WorldWideScience

Sample records for frequency doubling perimetry

  1. Comparison of Standard Automated Perimetry, Short-Wavelength Automated Perimetry, and Frequency-Doubling Technology Perimetry to Monitor Glaucoma Progression.

    Science.gov (United States)

    Hu, Rongrong; Wang, Chenkun; Gu, Yangshun; Racette, Lyne

    2016-02-01

    Detection of progression is paramount to the clinical management of glaucoma. Our goal is to compare the performance of standard automated perimetry (SAP), short-wavelength automated perimetry (SWAP), and frequency-doubling technology (FDT) perimetry in monitoring glaucoma progression.Longitudinal data of paired SAP, SWAP, and FDT from 113 eyes with primary open-angle glaucoma enrolled in the Diagnostic Innovations in Glaucoma Study or the African Descent and Glaucoma Evaluation Study were included. Data from all tests were expressed in comparable units by converting the sensitivity from decibels to unitless contrast sensitivity and by expressing sensitivity values in percent of mean normal based on an independent dataset of 207 healthy eyes with aging deterioration taken into consideration. Pointwise linear regression analysis was performed and 3 criteria (conservative, moderate, and liberal) were used to define progression and improvement. Global mean sensitivity (MS) was fitted with linear mixed models.No statistically significant difference in the proportion of progressing and improving eyes was observed across tests using the conservative criterion. Fewer eyes showed improvement on SAP compared to SWAP and FDT using the moderate criterion; and FDT detected less progressing eyes than SAP and SWAP using the liberal criterion. The agreement between these test types was poor. The linear mixed model showed a progressing trend of global MS overtime for SAP and SWAP, but not for FDT. The baseline estimate of SWAP MS was significantly lower than SAP MS by 21.59% of mean normal. FDT showed comparable estimation of baseline MS with SAP.SWAP and FDT do not appear to have significant benefits over SAP in monitoring glaucoma progression. SAP, SWAP, and FDT may, however, detect progression in different glaucoma eyes.

  2. The Groningen Longitudinal Glaucoma Study. II. A prospective comparison of frequency doubling perimetry, the GDx nerve fibre analyser and standard automated perimetry in glaucoma suspect patients

    NARCIS (Netherlands)

    Jansonius, Nomdo M.; Heeg, Govert P.

    We aimed to determine prospectively the incidence of abnormal test results on frequency doubling perimetry (FDT), the nerve fibre analyser (GDx) and standard automated perimetry (SAP) in a cohort of glaucoma suspect patients with normal findings for all these tests at baseline. Seventy glaucoma

  3. An evaluation of algorithms designed to classify the results from frequency doubling perimetry

    NARCIS (Netherlands)

    Muskens, RPHM; Heeg, GP; Jansonius, NM

    2004-01-01

    All previously published algorithms for the interpretation of frequency doubling perimetry test results were compared in full-threshold mode in a large group of glaucoma patients (n = 452) and normal subjects (n = 237). Areas under the receiver-operating characteristic (ROC) curve ranged from 0.86 t

  4. Frequency doubling perimetry screening mode compared to the full-threshold mode

    NARCIS (Netherlands)

    Stoutenbeek, R; Heeg, GP; Jansonius, NM

    2004-01-01

    The diagnostic performance of the frequency doubling perimetry (FDT) C20-1 screening mode was compared to that of the C20 full-threshold mode. For the number of defects p <1% in the total deviation plot, both modes appeared to perform similarly in terms of sensitivity, specificity, and area under th

  5. Learning effect of humphrey matrix frequency doubling technology perimetry in patients with ocular hypertension.

    Science.gov (United States)

    Centofanti, Marco; Fogagnolo, Paolo; Oddone, Francesco; Orzalesi, Nicola; Vetrugno, Michele; Manni, Gianluca; Rossetti, Luca

    2008-09-01

    To evaluate the learning effect of Frequency Doubling Technology (FDT) perimetry using the Humphrey Matrix-FDT perimetry (Matrix) 24-2 full-threshold program on patients with ocular hypertension experienced with standard automated perimetry. Twenty-four patients with ocular hypertension underwent 5 full-threshold Matrix tests at intervals of 5+/-2 days. Learning effect was defined as an improvement at results for duration, perimetric indices, foveal sensitivity, Glaucoma Hemifield Test, and the number of points with a Plearning effect. Test-retest variability was also calculated for each repetition as the mean of the point-to-point interindividual standard deviations. A learning effect was demonstrated for mean defect (P=0.031, analysis of variance) and foveal sensitivity (P=0.009) and it only affected the first test for both parameters. All the other parameters did not show any significant learning effect. The effect was independent from eccentricity and quadrant or hemifield sensitivities. The results of this study demonstrate that the learning effect for Matrix-FDT is mild and it may affect only the first test. Caution is needed in the analysis of the first Matrix-FDT examination and retest may be advisable in the presence of low mean defect.

  6. Humphrey visual field and frequency doubling perimetry in the diagnosis of early glaucoma.

    Directory of Open Access Journals (Sweden)

    Chandrasekhar G

    2003-01-01

    Full Text Available Purpose: To compare Humphrey Visual Field Analyzer (HVF and Frequency Doubling Perimetry (FDP testing in the diagnosis of early glaucoma. Methods: We performed HVF (24-2 standard full threshold and FDP (N-30 evaluations in 34 consecutive patients with early primary glaucoma and 96 normal subjects. Early glaucoma was defined on the basis of disc changes of glaucoma; the mean deviation on white-on-white perimetry had to be no worse than 6 decibels. Glaucomatous optic neuropathy was defined as a combination of cup-disc asymmetry of more than 0.2, notching, excavation, thinning or pallor of superior or inferior neuroretinal rims, retinal nerve fibre layer defects of the wedge or diffuse type and neuroretinal rim haemorrhage. Both the glaucoma patients and normal subjects had vision better than 6/9 with correction. They had no media opacities other than early nuclear sclerosis and no fundus pathology. Further, normal subjects were free of systemic diseases known to affect the retina or optic nerve, The sensitivity and specificity of HVF and FDP were calculated. Results: There were 44 eligible eyes among the 34 subjects. The glaucomatous disc findings included notch (n=8, pallor (n=21, thinning (n=23 and haemorrhage (n=1 of the neuroretinal rim. The sensitivity and the specificity of the HVF were 52.3% and 57.3% respectively. The sensitivity and the specificity of FDP were 65.9% and 61.5% respectively. Conclusion: The difference between FDP and HVF in the diagnosis of early glaucoma is not marked.

  7. Changes in Frequency-Doubling Perimetry in Patients with Type I Diabetes prior to Retinopathy

    Directory of Open Access Journals (Sweden)

    Isabel Pinilla

    2013-01-01

    Full Text Available Purpose. To evaluate the ability of frequency-doubling technology (FDT perimetry in detecting visual field defects in young adults with type I diabetes prior to retinopathy or with minor retinovascular changes. Methods. This comparative cross-sectional study included 30 healthy subjects and 73 age-matched patients with type I diabetes mellitus. All subjects underwent a full ocular examination including an FDT with the threshold C-20-5 strategy. Only one eye per subject was randomly included in the statistical analysis. FDT results and time to perform the test were compared between the groups. Results. The mean age was 27.1 years in the control group and 26.6 years in the diabetic group (P=0.875. The mean period from the onset of diabetes was 12.6±6.7 years, while minimal retinovascular changes were observed in 18 eyes. Mean deviation of FDT did not differ between the groups. Although global indices of FDT were within normal limits, pattern standard deviation of FDT was higher in the diabetic group (P=0.035. The area under the receiver operating characteristic curve was 0.647 for pattern standard deviation of FDT (standard error = 0.052; P=0.017. Conclusion. FDT can detect retinal dysfunctions in diabetic patients prior to the onset of significant vascular complications.

  8. Comparison of visual field test results obtained through Humphrey matrix frequency doubling technology perimetry versus standard automated perimetry in healthy children

    Directory of Open Access Journals (Sweden)

    Sibel Kocabeyoglu

    2013-01-01

    Full Text Available Aims : The aim of this study was to compare the visual field test results in healthy children obtained via the Humphrey matrix 24-2 threshold program and standard automated perimetry (SAP using the Swedish interactive threshold algorithm (SITA-Standard 24-2 test. Materials and Methods: This prospective study included 55 healthy children without ocular or systemic disorders who underwent both SAP and frequency doubling technology (FDT perimetry visual field testing. Visual field test reliability indices, test duration, global indices (mean deviation [MD], and pattern standard deviation [PSD] were compared between the 2 tests using the Wilcoxon signed-rank test and paired t-test. The performance of the Humphrey field analyzer (HFA 24-2 SITA-standard and frequency-doubling technology Matrix 24-2 tests between genders were compared with Mann-Whitney U-test. Results: Fifty-five healthy children with a mean age of 12.2 ± 1.9 years (range from 8 years to 16 years were included in this prospective study. The test durations of SAP and FDT were similar (5.2 ± 0.5 and 5.1 ± 0.2 min, respectively, P = 0.651. MD and the PSD values obtained via FDT Matrix were significantly higher than those obtained via SAP (P < 0.001, and fixation losses and false negative errors were significantly less with SAP (P < 0.05. A weak positive correlation between the two tests in terms of MD (r = 0.352, P = 0.008 and PSD (r = 0.329, P = 0.014 was observed. Conclusion: Children were able to complete both the visual test algorithms successfully within 6 min. However, SAP testing appears to be associated with less depression of the visual field indices of healthy children. FDT Matrix and SAP should not be used interchangeably in the follow-up of children.

  9. Multifocal and pattern-reversal visual evoked potentials vs. automated perimetry frequency-doubling technology matrix in optic neuritis

    Directory of Open Access Journals (Sweden)

    Marcella Nebbioso

    2013-01-01

    Full Text Available Background: To compare the usefulness of the traditional pattern-reversal Visual Evoked Potentials (VEP with multifocal VEP (mfVEP and Frequency-Doubling Technology (FDT perimetry in the evaluation of the ocular abnormalities induced by acute or subacute optic neuritis (ON. Materials and Methods: The test results of 24 ON patients were compared with those obtained in 40 normal control subjects. MfVEP recordings were obtained by using an Optoelectronic Stimulator that extracts topographic VEP using a pseudorandom m-sequence stimulus. Receiver operator characteristic (ROC curves were calculated to determine the sensitivity and specificity of abnormal values. Results: The frequency of the abnormal ocular findings differed in the ON patients according to the used technique. Reduced visual sensitivity was demonstrated in 12 eyes (54.5% using FDT perimetry; 17 eyes (77.2% showed decreased amplitude and/or an increase in the implicit time of the P1 wave in mfVEP and 20 eyes (90.9% showed an abnormal decrease in the amplitude and/or an increase in the latency of the P100 peak at VEP examination. The areas under the ROC curves ranged from 0.743 to 0.935, with VEP having the largest areas. The VEP and mfVEP amplitudes and latencies yielded the greatest sensitivity and specificity. Conclusions: The mfVEP and the FDT perimetry can be used for the evaluation and monitoring of visual impairment in patients with ON. The most sensitive and practical diagnostic tool in patients with ON is, however, the traditional VEP. The mfVEP can be utilized in those cases with doubtful or negative VEP results.

  10. Frequency-doubling technology perimetry and multifocal visual evoked potential in glaucoma, suspected glaucoma, and control patients

    Directory of Open Access Journals (Sweden)

    Kanadani FN

    2014-07-01

    Full Text Available Fabio N Kanadani,1 Paulo AA Mello,1 Syril K Dorairaj,2 Tereza CM Kanadani31Federal University of Sao Paulo, Sao Paulo, Brazil; 2Mayo Clinic, Department of Ophthalmology, Jacksonville, Florida, USA; 3Sao Jose University Hospital, Belo Horizonte, BrazilIntroduction: The gold standard in functional glaucoma evaluation is standard automated perimetry (SAP. However, SAP depends on the reliability of the patients’ responses and other external factors; therefore, other technologies have been developed for earlier detection of visual field changes in glaucoma patients. The frequency-doubling perimetry (FDT is believed to detect glaucoma earlier than SAP. The multifocal visual evoked potential (mfVEP is an objective test for functional evaluation.Objective: To evaluate the sensitivity and specificity of FDT and mfVEP tests in normal, suspect, and glaucomatous eyes and compare the monocular and interocuar mf VEP.Methods: Ninety-five eyes from 95 individuals (23 controls, 33 glaucoma suspects, 39 glaucomatous were enrolled. All participants underwent a full ophthalmic examination, followed by SAP, FDT, and mfVEP tests. Results: The area under the curve for mean deviation and pattern standard deviation were 0.756 and 0.761, respectively, for FDT, 0.564 and 0.512 for signal and alpha for interocular mfVEP, and 0.568 and 0.538 for signal and alpha for monocular mfVEP. This difference between monocular and interocular mfVEP was not significant. Conclusion: The FDT matrix was superior to mfVEP in glaucoma detection. The difference between monocular and interocular mfVEP in the diagnosis of glaucoma was not significant. Keywords: standard automated perimetry, electrophysiology, glaucomatous eyes

  11. Glaucoma progression detection with frequency doubling technology (FDT) compared to standard automated perimetry (SAP) in the Groningen Longitudinal Glaucoma Study.

    Science.gov (United States)

    Wesselink, Christiaan; Jansonius, Nomdo M

    2017-09-01

    To determine the usefulness of frequency doubling perimetry (FDT) for progression detection in glaucoma, compared to standard automated perimetry (SAP). Data were used from 150 eyes of 150 glaucoma patients from the Groningen Longitudinal Glaucoma Study. After baseline, SAP was performed approximately yearly; FDT every other year. First and last visit had to contain both tests. Using linear regression, progression velocities were calculated for SAP (Humphrey Field Analyzer) mean deviation (MD) and FDT MD and the number of test locations with a total deviation probability below p SAP and FDT classifications were made using a Mantel Haenszel chi-square test. Longitudinal signal-to-noise ratios (LSNRs) were calculated, per patient and per technique, defined as progression velocity divided by the standard deviation of the residuals. Mean (SD) follow-up was 6.4 (1.7) years; median (interquartile range [IQR]) baseline SAP MD -6.6 (-14.2 to -3.6) dB. On average 8.2 and 4.5 tests were performed for SAP and FDT, respectively. Median (IQR) MD slope was -0.16 (-0.46 to +0.02) dB/year for SAP and -0.05 (-0.39 to +0.17) dB/year for FDT. Mantel Haenszel chi-squares of SAP MD vs FDT MD and TD were 12.5 (p SAP MD (median -0.17 yr(-1) ) were better than those for FDT MD (-0.04 yr(-1) ; p = 0.010). FDT may be a useful technique for monitoring glaucoma progression in patients who cannot perform SAP reliably. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

  12. Combining Frequency Doubling Technology Perimetry and Scanning Laser Polarimetry for Glaucoma Detection.

    Science.gov (United States)

    Mwanza, Jean-Claude; Warren, Joshua L; Hochberg, Jessica T; Budenz, Donald L; Chang, Robert T; Ramulu, Pradeep Y

    2015-01-01

    To determine the ability of frequency doubling technology (FDT) and scanning laser polarimetry with variable corneal compensation (GDx-VCC) to detect glaucoma when used individually and in combination. One hundred ten normal and 114 glaucomatous subjects were tested with FDT C-20-5 screening protocol and the GDx-VCC. The discriminating ability was tested for each device individually and for both devices combined using GDx-NFI, GDx-TSNIT, number of missed points of FDT, and normal or abnormal FDT. Measures of discrimination included sensitivity, specificity, area under the curve (AUC), Akaike's information criterion (AIC), and prediction confidence interval lengths. For detecting glaucoma regardless of severity, the multivariable model resulting from the combination of GDx-TSNIT, number of abnormal points on FDT (NAP-FDT), and the interaction GDx-TSNIT×NAP-FDT (AIC: 88.28, AUC: 0.959, sensitivity: 94.6%, specificity: 89.5%) outperformed the best single-variable model provided by GDx-NFI (AIC: 120.88, AUC: 0.914, sensitivity: 87.8%, specificity: 84.2%). The multivariable model combining GDx-TSNIT, NAP-FDT, and interaction GDx-TSNIT×NAP-FDT consistently provided better discriminating abilities for detecting early, moderate, and severe glaucoma than the best single-variable models. The multivariable model including GDx-TSNIT, NAP-FDT, and the interaction GDx-TSNIT×NAP-FDT provides the best glaucoma prediction compared with all other multivariable and univariable models. Combining the FDT C-20-5 screening protocol and GDx-VCC improves glaucoma detection compared with using GDx or FDT alone.

  13. 青光眼中倍频视野检查与Octopus视野检查的相关性%Relationship between indices of Frequency Double Technique perimetry and Octopus perimetry in Glaucoma

    Institute of Scientific and Technical Information of China (English)

    金晓红; 孙兴怀

    2005-01-01

    目的评价青光眼中倍频视野计(Frequency Doubling Technique FDT)与传统自动视野计Octopus检查结果的相关性.方法35例正常对照,27例可疑青光眼患者,37例原发性开角型青光眼和50例正常眼压性青光眼患者进行FDT和Octopus检查.记录FDT视野检查的平均缺损(Mean Defect,MD)、图形标准偏差(Pattern Standard Deviation,PSD),Octopus视野检查中的平均缺损、丢失方差(Loss Variance,LV).应用线性回归分析计算回归方程及相关系数.结果原发性开角型青光眼中,FDT-MD与Octopus-MD,FDT-PSD与Octopus-LV均显著相关(r=0.828,r=0.758,P均<0.001).正常眼压性青光眼中,FDT-MD与Octopus-MD,PDT-PSD与Octopus-LV均显著相关(r=0.827,r=0.783,P均<0.001).结论FDT检查的各指标无论在POAG还是NTG中均与传统自动视野计Octopus有很好的相关性.

  14. [I have tested for you. Automated kinetic perimetry].

    Science.gov (United States)

    Chopin-Mouton, D

    2006-05-01

    We compared the kinetic perimetry of the Humphrey Field Anayzer and the Haag Streit Octopus 101 and assessed their use in relation to Goldmann perimetry. The Humphrey kinetic perimetry comes close to Goldmann perimetry and the Octopus shows clear advantages, notably in terms of ergonomics and its more sophisticated software. The Goldmann requires a high level of skill; examination time with the Humphrey and the Octopus is at least double the time required by a skilled Goldmann operator. The examiner can to a certain degree be passive during the static visual field examination, but is entirely active during the kinematic visual field examination. Therefore, contrary to static perimetry, the examination can only be performed by a physician. The future of automated kinematic perimetry depends on simplification of the software.

  15. The Groningen Longitudinal Glaucoma Study. I. Baseline sensitivity and specificity of the frequency doubling perimeter and the GDx nerve fibre analyser

    NARCIS (Netherlands)

    Heeg, GP; Blanksma, LJ; Hardus, PLLJ; Jansonius, NM

    2005-01-01

    Purpose: To describe the baseline data of a large cohort of patients included for follow-up with perimetry using the frequency doubling technique (FDT) and with quantification of the retinal nerve fibre layer as assessed by GDx, and to calculate the sensitivity and specificity of both devices from t

  16. Frequency doubling crystals

    Science.gov (United States)

    Wang, Francis; Velsko, Stephan P.

    1989-01-01

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  17. [Cartographic errors in perimetry].

    Science.gov (United States)

    Papoulis, C; Weber, J

    1991-02-01

    Cartography in perimetry repeats the problem of the cartography of the globe: it is impossible to transfer the image properly without a distortion of either angles, distances or areas. The projection type mostly used in perimetry leads to an enlargement and a tangential deformation that increases overproportionally towards the periphery (30 degrees: +5%, 60 degrees: +20%, 90 degrees: +57%). A circular scotoma, for example, is charted as en ellipse. In the opposite case, when a test point pattern is transferred from the perimetric chart to a perimetric sphere, there is a deformation, too. The distances between the test points are reduced in tangential direction, compared to the chart. A test grid with equidistant points on the chart appears in a rhomboid or rectangular distortion. This phenomenon has to be considered in the design of test point patterns for automatic static perimeters.

  18. Objective perimetry in glaucoma.

    Science.gov (United States)

    Klistorner, A; Graham, S L

    2000-12-01

    Objective perimetry in glaucoma is described using the multifocal pattern visually evoked potential (VEP). A multichannel recording technique was used to improve signal detection in healthy volunteers and assess its ability to detect glaucoma and early changes in patients with suspected glaucoma. Prospective, case-control study. Thirty healthy volunteers, 30 patients with suspected glaucoma, and 30 patients with glaucomatous visual field defects were tested. The VEP was recorded using cortically scaled, multifocal, pseudorandomly alternated pattern stimuli with the VERIS system (Electro-Diagnostic Imaging, Inc., San Francisco, CA). An array of four bipolar occipital electrodes provided four differently oriented channels for simultaneous recording. Signals were compared for different locations within the field up to 26 degrees of eccentricity. Healthy volunteers, patients with suspected glaucoma, and glaucoma patients with established visual field defects were tested, and results were compared with Humphrey visual fields (Humphrey Systems, Dublin, CA) performed on the same day. For reproducibility, five healthy volunteers were each tested on four separate days. The patients with suspected glaucoma and the established glaucoma patients were analyzed for intereye asymmetry of signals, and these data were compared with the asymmetry values of the healthy volunteers. Multiple recording channels significantly enhanced the recording of signals from parts of the visual field not reliably sampled with a single channel technique in all healthy volunteers, particularly along the horizontal meridian (P: < 0.001). Signal amplitude did not decline with age in healthy volunteers. Recordings showed good reproducibility within individuals. In all 30 glaucoma patients, the Humphrey visual field defects were well demonstrated by the VEP, and topographic location was strongly correlated (r(s) = 0.79). Despite large interindividual variations in amplitude, scotomas were well

  19. Frequency Doubling Broadband Light in Multiple Crystals

    Energy Technology Data Exchange (ETDEWEB)

    ALFORD,WILLIAM J.; SMITH,ARLEE V.

    2000-07-26

    The authors compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk off compensation, and with doubling in five crystals adjusted for offset phase matching frequencies. Using a plane-wave, dispersive numerical model of frequency doubling they study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance the offset phase matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second harmonic bandwidth. The walk off compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single crystal efficiency while maintaining broad bandwidth.

  20. Short wave–automated perimetry (SWAP versus optical coherence tomography in early detection of glaucoma

    Directory of Open Access Journals (Sweden)

    Zaky AG

    2016-09-01

    Full Text Available Adel Galal Zaky,1 Ahmed Tarek Yassin,2 Saber Hamed El Sayid1 1Ophthalmology Department, Faculty of Medicine, Menoufia University, Shebin El Kom, Menoufia, Egypt; 2Ophthalmology Department, Banha Educational Hospital, Banha, El Kalyobia, Egypt Objective: To assess the role and diagnostic effectiveness of optical coherence tomography (OCT and short wave–automated perimetry (SWAP to distinguish between normal, glaucoma suspects, and surely diagnosed glaucomatous eye.Background: Changes in the optic disc and retinal nerve fiber layer (RNFL often precede the appearance of visual field defect with standard automated perimetry. Unfortunately, RNFL defect can be difficult to identify during clinical examination. Early detection of glaucoma is still controversial, whether by OCT, SWAP, or frequency-doubling technology perimetry.Patients and methods: In this randomized controlled, consecutive, prospective study, a total 70 subjects (140 eyes were included in the study, divided into three groups: Group A, 10 healthy volunteers (20 eyes; Group B, 30 patients (60 eyes with glaucoma suspect; and Group C, 30 patients (60 eyes with already diagnosed glaucomatous eyes.Results: Average RNFL thickness was 75±9.0 in the glaucoma group, 99±15.5 in the control group, and 94±12 in glaucoma suspect. The inferior quadrant was the early parameter affected. There was significant correlation between visual field parameters and RNFL thickness in both glaucoma and glaucoma suspect groups.Conclusion: Both RNFL thickness measured by OCT and SWAP indices are good discrimination tools between glaucomatous, glaucoma suspect, and normal eyes. OCT parameters tend to be more sensitive than SWAP parameters. Keywords: OCT, SWAP, glaucoma, intraocular pressure, RNFL

  1. Intracavity frequency-doubled degenerate laser

    CERN Document Server

    Liew, Seng Fatt; Weiler, Sascha; Monjardin-Lopez, Jesus Fernando; Ramme, Mark; Redding, Brandon; Choma, Michael A; Cao, Hui

    2016-01-01

    We develop a green light source with low spatial coherence via intracavity frequency doubling of a solid-state degenerate laser. The second harmonic emission supports many more transverse modes than the fundamental emission, and exhibit lower spatial coherence. A strong suppression of speckle formation is demonstrated for both fundamental and second harmonic beams. Using the green emission for fluorescence excitation, we show the coherent artifacts are removed from the full-field fluorescence images. The high power, low spatial coherence and good directionality makes the green degenerate laser an attractive illumination source for parallel imaging and projection display.

  2. Cyclone frequency in east asia and double-cyclones

    OpenAIRE

    Umemoto, Tohru

    1982-01-01

    Japanese meteorologists call a certain type of cyclone "Futatsudama-teikiatsu" (Double-cyclone). The relationships between frequencies of extratropical cyclones and Double-cyclones were studied. Using a 2° latitude/longitude grid covering East Asia, three high frequency belts were found. Double-cyclones were classified into three types. Features of occurrence of these three types were discussed.

  3. Conical Double Frequency Emission by Femtosecond Laser Pulses from DKDP

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xi-Peng; JIANG Hong-Bing; TANG Shan-Chun; GONG Qi-Huang

    2009-01-01

    Conical double frequency emission is investigated by femtosecond laser pulses at a wavelength of 800nm in a DKDP crystal. It is demonstrated that the sum frequency of incident wave and its scattering wave accounts for the conical double frequency emission. The gaps on the conical rings are observed and they are very sensitive to the propagation direction, and thus could be used to detect the small angle deviation of surface direction.

  4. Spatial frequency doubling - Retinal or central. [visual illusion

    Science.gov (United States)

    Richards, W.; Felton, T. B.

    1973-01-01

    When a wide field is sinusoidally modulated both in space and in time, the spatial frequency of the pattern will appear doubled at high rates of modulation. Kelly (1966) proposed that this illusion is due to temporal integration of the nonlinear brightness response of the visual system. The anatomical locus of this temporal integrator is uncertain, and could be subcortical. Results indicate that spatial frequency doubling follows binocular disparity detection and is thus a cortical phenomenon.

  5. Multiorder nonlinear diffraction in frequency doubling processes

    DEFF Research Database (Denmark)

    Saltiel, Solomon M.; Neshev, Dragomir N.; Krolikowski, Wieslaw

    2009-01-01

    We analyze experimentally light scattering from 2 nonlinear gratings and observe two types of second-harmonic frequency-scattering processes. The first process is identified as Raman–Nath type nonlinear diffraction that is explained by applying only transverse phase-matching conditions. The angular...... position of this type of diffraction is defined by the ratio of the second-harmonic wavelength and the grating period. In contrast, the second type of nonlinear scattering process is explained by the longitudinal phase matching only, being insensitive to the nonlinear grating...

  6. Meta-analysis of the diagnostic efficiency of frequency-doubling technology for primary glaucoma

    Institute of Scientific and Technical Information of China (English)

    LIU Ting; HE Xiangge

    2007-01-01

    The overall diagnostic capabilities and utility of frequency-doubling technology (FDT) in patients with primary glaucoma,which was diagnosed by standard automated perimetry (SAP) and/or optic disc appearance as the gold standard,were assessed.A comprehensive electric retrieval in MEDLINE,EMBASE,Cochrane Library,BIOSIS,Previews,HMIC,IPA,OVID,CNKI,CBMdisc,VIP information,CMCC,CCPD,SSreader,21dmedia and manual retrieval in related textbooks,journals,congress articles and their references at home and abroad were performed to identify relevant articles in English or Chinese.The corresponding references were retrieved by means of electric retrieval and manual retrieval from different databases or materials.Criteria for inclusion or exclusion were established according to validity criteria for diagnostic studies published by the Cochrane Methods Group on Screening and Diagnostic Tests.The quality of the included articles was then assessed and characteristics were extracted.Statistical analysis was performed with Meta Test version 0.6 software to test the heterogeneity of the included articles.The appropriate effects model was selected to calculate pooled weighted sensitivity and specificity.Summary receiver operating characteristic (SROC)curve was drawn and the area under the curve (AUC)was calculated.Finally,sensitivity analysis was performed.Twenty-one studies out of 206 retrieved articles were included,with a total of 3172 patients.The reported sensitivity of FDT ranged from 0.51 to 1.00,and specificity from 0.58 to 1.00.The pooled weighted sensitivity and specificity of FDT with 95% confidence intervals (95% CI) after correction for standard error were 0.86 (0.80-0.90) and 0.87 (0.81-0.91),respectively.The AUC of SROC was 93.01%.Sensitivity analysis demonstrated no disproportionate influences of individual studies.The included articles are of good quality and FDT can be a highly efficient diagnostic test for primary glaucoma based on Meta-analysis.

  7. A frequency-doubled, pulsed laser system for rubidium manipulation

    CERN Document Server

    Dingjan, J; Beugnon, J; Jones, M P A; Bergamini, S; Messin, G; Browaeys, A; Grangier, P

    2005-01-01

    We have constructed a pulsed laser system for the manipulation of cold Rb atoms. The system combines optical telecommunications components and frequency doubling to generate light at 780 nm. Using a fast, fibre-coupled intensity modulator, output from a continuous laser diode is sliced into pulses with a length between 1.3 and 6.1 ns and a repetition frequency of 5 MHz. These pulses are amplified using an erbium-doped fibre amplifier, and frequency-doubled in a periodically poled lithium niobate crystal, yielding a peak power up to 12 W. Using the resulting light at 780 nm, we demonstrate Rabi oscillations on the F = 2 F=3-transition of a single 87Rb atom.

  8. Comparison of Size Modulation Standard Automated Perimetry and Conventional Standard Automated Perimetry with a 10-2 Test Program in Glaucoma Patients.

    Science.gov (United States)

    Hirasawa, Kazunori; Takahashi, Natsumi; Satou, Tsukasa; Kasahara, Masayuki; Matsumura, Kazuhiro; Shoji, Nobuyuki

    2017-08-01

    This prospective observational study compared the performance of size modulation standard automated perimetry with the Octopus 600 10-2 test program, with stimulus size modulation during testing, based on stimulus intensity and conventional standard automated perimetry, with that of the Humphrey 10-2 test program in glaucoma patients. Eighty-seven eyes of 87 glaucoma patients underwent size modulation standard automated perimetry with Dynamic strategy and conventional standard automated perimetry using the SITA standard strategy. The main outcome measures were global indices, point-wise threshold, visual defect size and depth, reliability indices, and test duration; these were compared between size modulation standard automated perimetry and conventional standard automated perimetry. Global indices and point-wise threshold values between size modulation standard automated perimetry and conventional standard automated perimetry were moderately to strongly correlated (p 33.40, p size modulation standard automated perimetry than with conventional standard automated perimetry, but the visual-field defect size was smaller (p size modulation-standard automated perimetry than on conventional standard automated perimetry. The reliability indices, particularly the false-negative response, of size modulation standard automated perimetry were worse than those of conventional standard automated perimetry (p size modulation standard automated perimetry than with conventional standard automated perimetry (p = 0.02). Global indices and the point-wise threshold value of the two testing modalities correlated well. However, the potential of a large stimulus presented at an area with a decreased sensitivity with size modulation standard automated perimetry could underestimate the actual threshold in the 10-2 test protocol, as compared with conventional standard automated perimetry.

  9. Volume of visual field assessed with kinetic perimetry and its application to static perimetry

    Directory of Open Access Journals (Sweden)

    Christoforidis JB

    2011-04-01

    Full Text Available John B ChristoforidisCollege of Medicine, The Ohio State University, Columbus, OH, USABackground: The purpose of this study was to quantify the volume of the kinetic visual field with a single unit that accounts for visual field area and differential luminance sensitivity.Methods: Kinetic visual field perimetry was performed with a Goldmann perimeter using I4e, I3e, I2e, and I1e targets. The visual fields of 25 normal volunteers (17 women, eight men of mean age 33.9 ± 10.1 (range 17–64 years were obtained and digitized. Isopter areas were measured with a method devised to correct cartographic distortion due to polar projection inherent in perimetry and are expressed in steradians. The third dimension of each isopter represents sensitivity to target luminance and was calculated as log (target luminance-1. If luminance is expressed in cd/m2, the values for the third dimension are 0.5 for I4e, 1.0 for I3e, 1.5 for I2e, and 2.0 for I1e. The resulting unit is a steradian (log 103 (cd/m2-1 which is referred to as a Goldmann. In addition, the visual fields of four patients with representative visual defect patterns were examined and compared with normal subjects.Results: Mean isopter areas for normal subjects were 3.092 ± 0.242 steradians for I4e, 2.349 ± 0.280 steradians for I3e, 1.242 ± 0.263 steradians for I2e, and 0.251 ± 0.114 steradians for the I1e target. Isopter volumes were 1.546 ± 0.121 Goldmanns for the I4e target, 1.174 ± 0.140 Goldmanns for I3e, 0.621 ± 0.131 Goldmanns for I2e, and 0.126 ± 0.057 Goldmanns for I1e. The total mean visual field volume in our study for the I target was 3.467 ± 0.371 Goldmanns.Conclusion: The volume of the island of vision may be used to quantify a visual field with a single value which contains information about both visual field extension and differential luminance sensitivity. This technique may be used to assess the progression or stability of visual field defects over time. A similar method may

  10. The relationship between standard automated perimetry and GDx VCC measurements

    NARCIS (Netherlands)

    N.J. Reus; H.G. Lemij (Hans)

    2004-01-01

    textabstractPURPOSE: To investigate the relationship between retinal light sensitivity measured with standard automated perimetry (SAP) and retardation of the peripapillary retinal nerve fiber layer (RNFL) measured with the GDx VCC (Laser Diagnostic Technologies, Inc., San Diego,

  11. A phase mixing model for the frequency-doubling illusion.

    Science.gov (United States)

    Wielaard, James; Smith, R Theodore

    2013-10-01

    We introduce a temporal phase mixing model for a description of the frequency-doubling illusion (FDI). The model is generic in the sense that it can be set to refer to retinal ganglion cells, lateral geniculate cells, as well as simple cells in the primary visual cortex (V1). Model parameters, however, strongly suggest that the FDI originates in the cortex. The model shows how noise in the response phases of cells in V1, or in further processing of these phases, easily produces observed behavior of FDI onset as a function of spatiotemporal frequencies. It also shows how this noise can accommodate physiologically plausible spatial delays in comparing neural signals over a distance. The model offers an explanation for the disappearance of the FDI at sufficiently high spatial frequencies via increasingly correlated coding of neighboring grating stripes. Further, when the FDI is equated to vanishing perceptual discrimination between asynchronous contrast-reversal gratings, the model proposes the possibility that the FDI shows a resonance behavior at sufficiently high spatial frequencies, by which it is alternately perceived and not perceived in sequential temporal frequency bands.

  12. Intracavity frequency-doubled green vertical external cavity surface emitting laser

    Institute of Scientific and Technical Information of China (English)

    Yanrong Song; Peng Zhang; Xinping Zhang; Boxia Yan; Yi Zhou; Yong Bi; Zhigang Zhang

    2008-01-01

    @@ An intracavity frequency-doubled vertical external cavity surface emitting laser (VECSEL) with green light is demonstrated. The fundamental frequency laser cavity consists of a distributed Bragg reflector (DBR) of the gain chip and an external mirror. A 12-mW frequency-doubled output has been reached at 540 nm with a nonlinear crystal LBO when the fundamental frequency output is 44 mW at 1080 nm. The frequency doubling efficiency is about 30%.

  13. Tunable Single-Frequency Intracavity Frequency-Doubled Ti:Sapphire Laser around 461 nm

    Institute of Scientific and Technical Information of China (English)

    李凤琴; 石柱; 李永民; 彭堃墀

    2011-01-01

    We demonstrate a tunable continuous-wave single frequency intracavity frequency-doubled Ti:sapphire laser.The highest output power of 280mW at 461.62nm is obtained by employing a type-I phase-matched BIBO crystal and the peak-to-peak fluctuation of the power is less than ±1% within three hours.The frequency stability is better than ±2.22 MHz over 10min when the laser is locked to a confocal Fabry-Perot cavity.A three-plate birefringent filter allows for the tunable range from 457nm to 467nm,which covers the absorption line of the strontium atoms(460.86nm).%We demonstrate a tunable continuous-wave single frequency intracavity frequency-doubled Ti:sapphire laser. The highest output power of 280mW at 461.62nm is obtained by employing a type-I phase-matched BIBO crystal and the peak-to-peak fluctuation of the power is less than ±1% within three hours. The frequency stability is better than ±2.22MHz over lOmin when the laser is locked to a confocal Fabry-Perot cavity. A three-plate birefringent filter allows for the tunable range from 457nm to 467 nm, which covers the absorption line of the strontium atoms (460.86 nm).

  14. Double-loop frequency selective surfaces for multi frequency division multiplexing in a dual reflector antenna

    Science.gov (United States)

    Wu, Te-Kao (Inventor)

    1994-01-01

    A multireflector antenna utilizes a frequency-selective surface (FSS) in a subreflector to allow signals in two different RF bands to be selectively reflected back into a main reflector and to allow signals in other RF bands to be transmitted through it to the main reflector for primary focus transmission. A first approach requires only one FSS at the subreflector which may be an array of double-square-loop conductive elements. A second approach uses two FSS's at the subreflector which may be an array of either double-square-loop (DSL) or double-ring (DR). In the case of DR elements, they may be advantageously arranged in a triangular array instead of the rectangular array for the DSL elements.

  15. [New diagnostic aids in automatic perimetry].

    Science.gov (United States)

    Weber, J; Papoulis, C; Schmitz, A

    1993-04-01

    The Conformity Analysis is a new procedure for objective recognition of specific defect patterns in automated perimetry. The "Conformity Index," the measure of conformity between the distribution of defect values and several standard defect patterns, is calculated from the ratio of global variance and mean variance in particular regions. Using 68 visual fields from 68 normal persons, we determined normal values and limits of the Conformity Index for seven standard defect patterns: hemifields right-left, hemifields upper-lower, quadrants, sectors, rings with 5 degrees and 10 degrees radius interval and the perimetric nerve fiber bundles of Weber and Ulrich. The evaluation of 148 visual fields (68 normal eyes, 80 eyes with chronic glaucoma and all stages of damage) by both the Conformity Index and two experienced clinicians revealed an identical result in 89%. Using the Conformity Analysis in 37 cases of pituitary adenoma, we could objectively identify quadrants, sectors and hemifields right-left to be the most common defect patterns in this disease. In glaucoma fields with marked damage (n = 46), the most frequent pathological Conformity Index was the index for perimetric nerve fiber bundles.

  16. High frequency optical pulse generation by frequency doubling using polarization rotation

    Science.gov (United States)

    Liu, Yang

    2016-05-01

    In this work, we propose and experimentally characterize a stable 40 GHz optical pulse generation by frequency doubling using polarization rotation in a phase modulator (PM). Only half the electrical driving frequency is required (i.e. 20 GHz); hence the deployment cost can be reduced. Besides, precise control of the bias of the PM is not required. The generated optical pulses have a high center-mode-suppression-ratio (CMSR) of  >  28 dB. The single sideband (SSB) noise spectrum is also measured, and the time-domain waveforms under different CMSRs are also analyzed and discussed.

  17. Operation of the CAPRICE electron cyclotron resonance ion source applying frequency tuning and double frequency heating.

    Science.gov (United States)

    Maimone, F; Tinschert, K; Celona, L; Lang, R; Mäder, J; Rossbach, J; Spädtke, P

    2012-02-01

    The properties of the electromagnetic waves heating the electrons of the ECR ion sources (ECRIS) plasma affect the features of the extracted ion beams such as the emittance, the shape, and the current, in particular for higher charge states. The electron heating methods such as the frequency tuning effect and the double frequency heating are widely used for enhancing the performances of ECRIS or even for the routine operation during the beam production. In order to better investigate these effects the CAPRICE ECRIS has been operated using these techniques. The ion beam properties for highly charged ions have been measured with beam diagnostic tools. The reason of the observed variations of this performance can be related to the different electromagnetic field patterns, which are changing inside the plasma chamber when the frequency is varying.

  18. Diagnostic ability of Humphrey perimetry, Octopus perimetry, and optical coherence tomography for glaucomatous optic neuropathy.

    Science.gov (United States)

    Monsalve, B; Ferreras, A; Calvo, P; Urcola, J A; Figus, M; Monsalve, J; Frezzotti, P

    2016-11-11

    PurposeTo evaluate and compare the diagnostic accuracy of the Humphrey Field Analyzer (HFA), Octopus perimetry, and Cirrus OCT for glaucomatous optic neuropathy.MethodsEighty-eight healthy individuals and 150 open-angle glaucoma patients were consecutive and prospectively selected. Eligibility criteria for the glaucoma group were intraocular pressure ≥21 mm Hg and glaucomatous optic nerve head morphology. All subjects underwent a reliable standard automated perimetry with the HFA and Octopus perimeter, and were imaged with the Cirrus OCT. Receiver-operating characteristic (ROC) curves were plotted for the threshold values and main indices of the HFA and Octopus, the peripapillary retinal nerve fiber layer thicknesses, and the optic nerve head parameters. Sensitivities at 85 and 95% fixed-specificities were also calculated. The best areas under the ROC curves (AUCs) were compared using the DeLong method.ResultsIn the glaucoma group, mean deviation (MD) was -5.42±4.6 dB for HFA and 3.90±3.6 dB for Octopus. The MD of the HFA (0.966; P<0.001), mean sensitivity of the Octopus (0.941; P<0.001), and average cup-to-disc (C/D) ratio measured by the Cirrus OCT (0.958; P<0.001) had the largest AUCs for each test studied. There were no significant differences among them. Sensitivities at 95% fixed-specificity were 82% for pattern standard deviation of the HFA, 81.3% for average C/D ratio of OCT, and 80% for the MD of the Octopus.ConclusionsHFA, Octopus, and Cirrus OCT demonstrated similar diagnostic accuracies for glaucomatous optic neuropathy. Visual field and OCT provide supplementary information and thus these tests are not interchangeable.Eye advance online publication, 11 November 2016; doi:10.1038/eye.2016.251.

  19. Long-pulse, single-frequency 1064 nm laser and frequency doubling

    Institute of Scientific and Technical Information of China (English)

    Xiafei Xu; Gang Xie; Yanhua Lu; Lei Zhang; Min Wan

    2015-01-01

    An all-solid-state single-frequency 1064 nm laser with a 100 μs pulse width, 500 Hz repetition rate and 700 m J single pulse energy is designed using seed injection and a three-stage master oscillator power amplifier(MOPA) construction.Using this as a basis, research on long-pulse laser frequency doubling is carried out. By designing and optimizing the lithium triborate(LBO) crystal, the theoretically calculated maximum conversion efficiency ηmax reaches 68% at M2=1, while ηminis 33% at M2=3. Generation of 212 m J pulses of green light with a repetition rate as high as500 Hz is obtained from a fundamental energy of 700 m J. The experimental conversion efficiency reaches 31% and the power stability is better than±1%.

  20. Efficient frequency doubling at 776 nm in a ring cavity

    Science.gov (United States)

    Han, Zhen-Hai; Liu, Shi-Long; Liu, Shi-Kai; Ding, Dong-Sheng; Zhou, Zhi-Yuan

    2017-08-01

    We report efficient frequency doubling (FD) at 776 nm using periodically poled LiNbO3 (PPLN) in a ring cavity pumped by a commercial erbium-doped fiber amplifier (EDFA) operating at 1552 nm. Two sets of input couplers are used that have been optimized to operate in the low pump and high pump regimes. The maximum conversion efficiencies measured for these couplers are 65.8% (transmittance T=4.5%) and 65.9% (T=9.1%). The internal conversion efficiencies are 85.0% and 88.2%, respectively, after the mode-matching efficiency and filtering transmittance have been taken into account. The maximum output powers obtained for the two couplers are 333 mW and 602 mW at pump powers of 535 mW and 999 mW, respectively. Coupling efficiency of more than 80% to single mode fibers indicates the high beam quality of the FD laser. This FD laser will be useful for quantum optics experiments in the telecommunications band and atomic physics experiments.

  1. Bacterial colonization of double J stents and bacteriuria frequency

    Directory of Open Access Journals (Sweden)

    Berat Cem Ozgur

    2013-12-01

    Full Text Available Stents and catheters are widely used in urology. In this study, the frequency of double J (DJ stent colonization and stent-associated bacteriuria was investigated. Between June 2011 and June 2012, 130 patients (17–72 years old who underwent DJ stenting were enrolled in the study. Surgeries prior to stenting included stone extraction/lithotripsy, endopyelotomy, and diagnostic ureteroscopy. Prior to stenting, sterile urine samples were obtained, and urinary cultures were performed upon removal of the DJ stents, the second procedure. DJ stent cultures were also performed. Sixty-three stents were inserted into the right ureter and 67 into the left ureter of the patients. Cultures showed bacterial colonization in 10 (7.7% cases. There was no significant association between positive stent culture and patient age, sex, or stent laterality. The rate of colonization was 2.2%, 2.9%, and 25% when indwelling time was less than 4 weeks, 4–6 weeks, and more than 6 weeks, respectively. In the present study, the rate of infection associated with a DJ stent and urinary infection was not very high. However, bacterial colonization increases significantly with indwelling time of the stent, and sterile culture of urine does not rule out colonization of the stent. Bacteriological investigation showed very low rates of colonization within 6 weeks after the insertion of stents, indicating that ureteral stents can be used safely within that time period.

  2. Quantitative perimetry under binocular viewing conditions in microstrabismus

    NARCIS (Netherlands)

    M.V. Joosse (Maurits); H.J. Simonsz (Huib); H.M. van Minderhout; P.T.V.M. de Jong (Paulus); B. Noordzij (Bastiaantje); P.G.H. Mulder (Paul)

    1997-01-01

    textabstractIn order to elucidate the type, size and depth of suppression scotomata in microstrabismus and small angle convergent strabismus, we performed binocular static perimetry in 14 subjects with strabismus and four normal observers. The strabismic cases had an objective angle of convergent

  3. The effect of cataract on eye movement perimetry

    NARCIS (Netherlands)

    G. Thepass; J.J.M. Pel (Johan); K.A. Vermeer (Koen); O. Creten; S. Bryan (Stirling); H.G. Lemij (Hans); J. van der Steen (Hans)

    2015-01-01

    textabstractPurpose. To determine how different grades of cataract affect sensitivity threshold and saccadic reaction time (SRT) in eye movement perimetry (EMP). Methods. In EMP, the visual field is tested by assessing the saccades that a subject makes towards peripheral stimuli using an eye

  4. Multifocal objective perimetry in the detection of glaucomatous field loss.

    Science.gov (United States)

    Goldberg, Ivan; Graham, Stuart L; Klistorner, Alexander I

    2002-01-01

    To test the ability of a new type of multifocal objective perimetry to identify glaucomatous visual field defects. A multichannel visual evoked potential was recorded using the ObjectiVision Accumap perimeter. One hundred patients (age, 62.2 +/- 9.8 years, mean MD -6.5 +/- 4.17 dB) with open-angle glaucoma and confirmed glaucomatous visual field defects were tested and compared with the normal database of 100 normal subjects (age, 58.9 +/- 10.7 years). Both eyes were tested, but for determining sensitivity the eye with the lesser field defect was chosen if both qualified. The amplitude and intereye asymmetry coefficient for each zone of the field were calculated. A mean amplitude and multifocal objective perimetry severity index was calculated for each subject. In 95 of 100 (95%) patients with glaucoma Humphrey field defects were correlated with visual evoked potential amplitude reductions identifying a cluster of three or more abnormal zones. In two of five remaining patients with glaucoma the defect was detected on the intereye asymmetry analysis. Topographic location was well correlated with Humphrey fields. Mean amplitude was significantly reduced in 86 of the glaucoma cases (86%). The glaucoma severity index was abnormal in 93 glaucoma cases and showed a correlation with Humphrey MD (r = 0.67 right eyes, 0.69 left eyes). In 37 glaucoma cases with no scotoma by definition in the fellow eye, 22 (59.4%) had an abnormal multifocal objective perimetry, whereas only eight had some other aspect of their Humphrey visual field flagged as abnormal. Multifocal objective perimetry can assess the visual field and identify glaucomatous visual field defects. It may have the potential for identifying defects earlier than conventional perimetry.

  5. Static and flicker perimetry in age-related macular degeneration.

    Science.gov (United States)

    Luu, Chi D; Dimitrov, Peter N; Wu, Zhichao; Ayton, Lauren N; Makeyeva, Galina; Aung, Khin-Zaw; Varsamidis, Mary; Robman, Luba; Vingrys, Algis J; Guymer, Robyn H

    2013-05-01

    The relationship between clinical severity of age-related macular degeneration (AMD) and macular function has not been well established. In this study, we investigated the correlation between clinical severity and functional deficits as detected by static and flicker perimetry. This cross-sectional study consisted of 279 AMD subjects and 24 control participants. AMD subjects were allocated into 1 of 10 AMD severity groups depending on the status of the designated study eye and the fellow eye, as assessed by color fundus photographs. Visual acuity, and static and flicker perimetry were tested on one eye during the same session. The geometric means, SDs, and percentage of abnormal eyes of static and flicker sensitivity of each AMD severity group were determined and compared. The pattern of change in sensitivity and percentage of abnormal eyes for static perimetry across all AMD severity groups were similar to flicker perimetry. Eyes with drusen > 125 μm (P[static] = 0.018, P[flicker] = 0.024), drusenoid epithelial detachment (P[static and flicker] static and flicker] static and flicker sensitivities compared to normal eyes. Static (β-coefficient -1.59, 95% confidence interval [CI] -4.78-1.60) and flicker (β-coefficient -1.29, 95% CI -4.66-2.08) sensitivities declined at a similar rate in eyes that showed clinical signs of progression. Static and flicker perimetry were affected similarly across the spectrum of AMD severity, and methods appeared to be valid techniques for assessing retinal sensitivity in AMD once drusen > 125 μm are present, but before the development of late AMD.

  6. Effect of yellow-tinted intraocular lens on standard automated perimetry and short wavelength automated perimetry in patients with glaucoma

    Directory of Open Access Journals (Sweden)

    Naveed Nilforushan

    2014-01-01

    Conclusions: In mild to moderate glaucoma patients with cataracts, the perimetry indices of SWAP testing improved after phacoemulsification and yellow-tinted IOL implantation. This suggests that the yellow-tinted IOLs have less effect on SWAP testing than visually significant cataracts.

  7. Theory modeling and experimental research of external-cavity frequency doubling technology of short pulse laser

    Science.gov (United States)

    Duan, Cun-li; Zhang, Su-juan; He, Jiang-long

    2011-06-01

    Q-switched Short pulse laser has been widely applied in many fields, such as optical ranging, remote sensing, communications, nonlinear optics and spectroscopy etc. Q-switched Nd3+: YAG laser, with its high thermal conductivity and resistance to damage threshold, longer energy levels were generally used especially. Second harmonics generation was usually obtained through optical nonlinear effects in crystal. To the frequency doubling technology, poor conversion efficiency and multi-output frequency are the main problems. Researchers focus more on phase and group velocity matching induced by nonlinear effects, but pays less attention on theoretical modeling and numerical calculation of factors affecting frequency doubling of pulsed laser. In this article, nonlinear effects of double frequency crystals in Q-switched Nd3+: YAG laser was first analyzed in theory, then we deduced the relation expressions between factors affecting the efficiency of frequency doubling( thickness of frequency doubling crystal, cross section area of incident beam, power of the fundamental field, phase matching of incidence light)and double frequency efficiency. Secondly, taken KTP Crystal for example; numerical results and theirs' corresponding curves on these relation expressions was calculated and drawn with MATLAB software. These findings can be used for processing the specific requests of frequency doubling crystal. Finally, Theory modeling and numerical calculation were tested in experiment. The experiment results are in good agreement with those obtained in theory.

  8. High power, continuous-wave, single frequency fiber amplifier at 1091 nm and frequency doubling to 545.5 nm

    CERN Document Server

    Stappel, M; Kolbe, D; Walz, J

    2012-01-01

    We present a high power single-frequency ytterbium fiber amplifier system with an output power of 30 W at 1091 nm. The amplifier system consists of two stages, a preamplifier stage in which amplified spontaneous emission is efficiently suppressed (>40 dB) and a high power amplifier with an efficiency of 52 %. Two different approaches of frequency doubling are compared. We achieve 8.6 W at 545.5 nm by single-pass frequency doubling in a MgO-doped periodically poled stoichiometric LiTaO3 and up to 19.3 W at 545.5 nm by frequency doubling with a lithium-triborate (LBO) crystal in an external enhancement cavity.

  9. Single-frequency and tunable operation of a continuous intracavity-frequency-doubled singly resonant optical parametric oscillator.

    Science.gov (United States)

    My, Thu-Hien; Drag, Cyril; Bretenaker, Fabien

    2008-07-01

    A widely tunable continuous intracavity-frequency-doubled singly resonant optical parametric oscillator based on MgO-doped periodically poled stoichiometric lithium tantalate crystal is described. The idler radiation resonating in the cavity is frequency doubled by an intracavity BBO crystal. Pumped in the green, this system can provide up to 485 mW of single-frequency orange radiation. The system is continuously temperature tunable between 1170 and 1355 nm for the idler, 876 and 975 nm for the signal, and between 585 and 678 nm for the doubled idler. The free-running power and frequency stability of the system have been observed to be better than those for a single-mode dye laser.

  10. The green light generation by self-frequency-doubled Yb:YCOB crystal

    CERN Document Server

    Fang, Qiannan; Zhang, Huaijin; Wang, Jiyang

    2016-01-01

    Taking advantages of the broad emission bands of a Yb3+ doped calcium yttrium oxoborate (Yb:YCOB) crystal cut along the optimized direction out of principle planes with the maximum effective nonlinear coefficient, the self-frequency-doubled green light based on the self-frequency-doubling behavior of Yb:YCOB was achieved with a maximum output power of 710 mW at 523 nm.

  11. Quantum frequency doubling based on tripartite entanglement with cavities

    Science.gov (United States)

    Juan, Guo; Zhi-Feng, Wei; Su-Ying, Zhang

    2016-02-01

    We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cavities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the transmission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network. Project supported by the National Natural Science Foundation of China (Grant No. 91430109), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111401110004), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011005-3).

  12. Quad-Chip Double-Balanced Frequency Tripler

    Science.gov (United States)

    Lin, Robert H.; Ward, John S.; Bruneau, Peter J.; Mehdi, Imran; Thomas, Bertrand C.; Maestrini, Alain

    2010-01-01

    Solid-state frequency multipliers are used to produce tunable broadband sources at millimeter and submillimeter wavelengths. The maximum power produced by a single chip is limited by the electrical breakdown of the semiconductor and by the thermal management properties of the chip. The solution is to split the drive power to a frequency tripler using waveguides to divide the power among four chips, then recombine the output power from the four chips back into a single waveguide. To achieve this, a waveguide branchline quadrature hybrid coupler splits a 100-GHz input signal into two paths with a 90 relative phase shift. These two paths are split again by a pair of waveguide Y-junctions. The signals from the four outputs of the Y-junctions are tripled in frequency using balanced Schottky diode frequency triplers before being recombined with another pair of Y-junctions. A final waveguide branchline quadrature hybrid coupler completes the combination. Using four chips instead of one enables using four-times higher power input, and produces a nearly four-fold power output as compared to using a single chip. The phase shifts introduced by the quadrature hybrid couplers provide isolation for the input and output waveguides, effectively eliminating standing waves between it and surrounding components. This is accomplished without introducing the high losses and expense of ferrite isolators. A practical use of this technology is to drive local oscillators as was demonstrated around 300 GHz for a heterodyne spectrometer operating in the 2-3-THz band. Heterodyne spectroscopy in this frequency band is especially valuable for astrophysics due to the presence of a very large number of molecular spectral lines. Besides high-resolution radar and spectrographic screening applications, this technology could also be useful for laboratory spectroscopy.

  13. Internal oscillation frequencies and anharmonic effects for the double sine-Gordon kink

    DEFF Research Database (Denmark)

    Salerno, M.; Samuelsen, Mogens Rugholm

    1989-01-01

    A simple derivation of the small oscillation frequency around 4π-kink solutions of the double sine-Gordon equation is presented. Small corrections to these frequencies due to anharmonic effects are also numerically and analytically investigated. The analysis is based on energetic considerations...

  14. Improved automated perimetry performance following exposure to Mozart.

    Science.gov (United States)

    Fiorelli, V Macedo Batista; Kasahara, N; Cohen, R; França, A Santucci; Della Paolera, M; Mandia, C; de Almeida, G Vicente

    2006-05-01

    To evaluate the performance on automated perimetry (AP) after listening to a Mozart sonata in normal subjects naive to AP. 60 naive normal subjects underwent AP (SITA 24-2). The study group (30 subjects) underwent AP after listening to Mozart's Sonata for Two Pianos in D Major and the control group (30 subjects) underwent AP without previous exposure to the music. The study group had significantly less fixation loss, false positive, and false negative rates compared to controls (p Mozart seems to improve AP performance in normal naive subjects.

  15. Efficient generation of 3.5W laser light at 515nm by frequency doubling a single-frequency high power DBR tapered diode laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Hansen, Anders Kragh; Müller, André

    2017-01-01

    More than 3.5 W of green light at 515 nm is generated by frequency doubling a single-frequency high power DBR tapered diode laser. The frequency doubling is performed in a cascade of PPMgLN and PPMgSLT crystals in order to reach high power and avoid thermal effects present in PPMgLN at high power...

  16. A double expansion method for the frequency response of finite-length beams with periodic parameters

    Science.gov (United States)

    Ying, Z. G.; Ni, Y. Q.

    2017-03-01

    A double expansion method for the frequency response of finite-length beams with periodic distribution parameters is proposed. The vibration response of the beam with spatial periodic parameters under harmonic excitations is studied. The frequency response of the periodic beam is the function of parametric period and then can be expressed by the series with the product of periodic and non-periodic functions. The procedure of the double expansion method includes the following two main steps: first, the frequency response function and periodic parameters are expanded by using identical periodic functions based on the extension of the Floquet-Bloch theorem, and the period-parametric differential equation for the frequency response is converted into a series of linear differential equations with constant coefficients; second, the solutions to the linear differential equations are expanded by using modal functions which satisfy the boundary conditions, and the linear differential equations are converted into algebraic equations according to the Galerkin method. The expansion coefficients are obtained by solving the algebraic equations and then the frequency response function is finally determined. The proposed double expansion method can uncouple the effects of the periodic expansion and modal expansion so that the expansion terms are determined respectively. The modal number considered in the second expansion can be reduced remarkably in comparison with the direct expansion method. The proposed double expansion method can be extended and applied to the other structures with periodic distribution parameters for dynamics analysis. Numerical results on the frequency response of the finite-length periodic beam with various parametric wave numbers and wave amplitude ratios are given to illustrate the effective application of the proposed method and the new frequency response characteristics, including the parameter-excited modal resonance, doubling-peak frequency response

  17. Active and passive stabilization of a high-power UV frequency-doubled diode laser

    CERN Document Server

    Eismann, Ulrich; Simeonidis, Konstantinos; Keller, Felix; Rohde, Felix; Opalevs, Dmitrijs; Scholz, Matthias; Kaenders, Wilhelm; Stuhler, Jürgen

    2016-01-01

    We present a resonantly frequency-doubled tapered amplified semiconductor laser system emitting up to 2.6 W blue light at 400 nm. The output power is stable on both short and long timescales with 0.12% RMS relative intensity noise, and less than 0.15%/h relative power loss over 16 hours of free running continuous operation. Furthermore, the output power can be actively stabilized, and the alignment of the input beams of the tapered amplifier chip, the frequency doubling cavity and-in case of fiber output-the fiber can be optimized automatically using computer-controlled mirrors.

  18. Intracavity frequency doubling of CW Ti:Sapphire laser utilising BiBO nonlinear crystal

    DEFF Research Database (Denmark)

    Thorhauge, Morten; Mortensen, Jesper Liltorp; Tidemand-Lichtenberg, Peter

    Utilising BiBO nonlinear crystal frequency doubling a Ti:Sapphire CW laser gave 100 mW at 405 nm and 53 mW at 392 nm. Stability proved excellent without servo control. Broad tunability was shown around 392 nm.......Utilising BiBO nonlinear crystal frequency doubling a Ti:Sapphire CW laser gave 100 mW at 405 nm and 53 mW at 392 nm. Stability proved excellent without servo control. Broad tunability was shown around 392 nm....

  19. Changing and predicting the frequency of double wall carbon nanotubes oscillator

    Directory of Open Access Journals (Sweden)

    Xing Huang

    2017-06-01

    Full Text Available Double wall carbon nanotubes have been considered as potential candidate for ultra-high frequency oscillator. However, the exact frequency change versus the nanotubes’ shape has not been detailed discussed. In this article, a series of double wall carbon nanotubes oscillators are investigated using molecular dynamics simulation. We find that, by changing the tube length and radius, the oscillation frequency can be easily modified. To better understand the simulation result above, a theoretical model with maximum main force approximation is introduced. Then the tendency for the frequency change can be well interpreted. Moreover, we find the effective force increases linearly with the tube radius. After a careful derivation, a universal formula is given, which can predict the oscillation period with a good accuracy.

  20. 倍频视野检测在40岁以上人群中筛查青光眼的价值%The value of frequency doubling perimetry in glaucoma screening of aged 40 or more population

    Institute of Scientific and Technical Information of China (English)

    李建军; 徐亮; 张蓉秀; 孙秀英; 杨桦; 邹洋; 赵家良

    2005-01-01

    目的探讨倍频视野检测(FDP)程序在40岁以上自然人群中筛查青光眼的敏感性和特异性.方法 2001年5至10月对北京市大兴区榆垡乡3个自然村及市区北部4个社区40岁以上居民4439人进行青光眼筛查.所有受试者均用倍频视野计的C-20-1筛查程序检测视野.对可疑青光眼者在非筛查日进行Octopus阈值视野、前房角镜及视乳头立体照相检查.根据Octopus视野检测的平均缺损(MD)值,将筛查出的青光眼分为轻、中、重三级.FDP的分析指标包括FDP检测时间、异常位点数、FDP计分、4个象限FDP计分等.正常人随机选一只眼的数据用于分析;双眼青光眼患者选择视神经或Octopus视野损害较轻的眼用于分析.结果 4330例(97.5%)用于FDP分析.以FDP结果≥1个点异常为临界点,将人群分为正常人与青光眼两组,则FDP检查青光眼的敏感性为50.7%(72/142),特异性为96.6%(2260/2340),受试者工作特征曲线下面积(AUC)为0.7,阳性预测值47.7%,阴性预测值96.9%,阳性似然比14.8,阴性似然比0.5.若除外无青光眼性视神经与Octopus视野损害的青光眼,则FDP检测青光眼的敏感性为76.4%,AUC为0.9, 阳性预测值为40.7%,阴性预测值99.2%,阳性似然比22.3,阴性似然比0.2.检测轻、中、重度青光眼的敏感性分别为54.2%、76.0%、100.0%.FDP视野的4个象限计分与Octopus视野4个相应象限的MS呈显著负相关(Rs分别为-0.732、-0.628、-0.639、-0.679,均P<0.01).结论 C-20-1 FDP筛查程序适用于在大规模人群中筛查青光眼,具有较高的特异性;对中、重度青光眼性视野缺损患者具有良好的敏感性.

  1. Study on 660-nm quasi-continuous-wave intracavity frequency-doubled Nd:YAG laser

    Institute of Scientific and Technical Information of China (English)

    Tao Wang(王涛); Jianquan Yao(姚建铨); Baigang Zhang(张百钢); Guiyan Zang(臧贵艳); Peng Wang(王鹏); Yizhong Yu(于意仲)

    2003-01-01

    A quasi-continuous-wave intracavity frequency-doubled Nd:YAG laser which operates at 660 nm is studied.By using a flat-flat laser cavity, 2 Kr-lamps, KTP crystal and an acousto-optically Q-switch, 2-W outputpower at 660 nm is obtained. The relationship between laser cavity length and output power is analyzed.

  2. Passively Q-switched Self-frequency Doubling NYAB laser with GaAs Saturable Absorber

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shengzhi(赵圣之); ZHENG Jiaan(郑加安); CHEN Lei(陈磊); CHENG Zhenxiang(程振祥); CHEN Huanchu(陈焕矗)

    2002-01-01

    By using a passive Q-switch with GaAs saturable absorber, the Q-switched self-frequency doubling NYAB laser at 0.531μm has been successfully realized. The pulse width and the single pulse energy are measured. The numerical solutions of the coupling wave rate equations are in agreement with the experimental results.

  3. Multifocal pattern VEP perimetry: analysis of sectoral waveforms.

    Science.gov (United States)

    Klistorner, A I; Graham, S L

    1999-01-01

    The objective detection of local visual field defects using multi-focal pattern visual evoked potentials (VEP) has recently been described. The individual waveforms show variable polarity in different parts of the visual field due to underlying cortical convolutions. Normal trace arrays were examined to determine if certain areas of similar waveform could be grouped for analysis, while minimising cancellation of data. The VEP was assessed using multi-focal pseudo-randomly alternated pattern stimuli which were cortically scaled in size. Bipolar occipital electrodes were used for recording. Waveforms were compared for different locations within the field up to 25 degrees of eccentricity. Analysis of sectors showing similarly shaped waveforms was performed. Twelve normal subjects were studied. Grouping waveforms by sectors of similar waveform increased the total calculated upper hemifield amplitude by 60%, compared with simple summations of responses for the whole hemifield. The inferior hemifield showed more consistent waveforms throughout, with the amplitude only increasing by 11% with sectoral summation. Intra-subject variability (10.6%) is less for sectors than for individual points (17.3%). Inter-subject amplitude differences are high, calculated at 56% for individual points and 45% for sectors. Due to differences in waveform as a result of underlying cortical anatomy, individual VEP responses from multifocal recordings should be grouped as sectors along the vertical meridian and above and below the horizontal, rather than by hemifields or quadrants. This finding is significant if one is considering within-field grouping strategies similar to the glaucoma hemifield test used in conventional perimetry, or reporting derived overall VEP amplitudes and latencies from a multifocal recording. Large amplitude variations between individuals and small signals from horizontal and upper field seen in single channel recording, still limit the application of this technique as

  4. Clinical usefulness of transpapillary removal of common bile duct stones by frequency doubled double pulse Nd: YAG laser

    Institute of Scientific and Technical Information of China (English)

    Tae Hyeon Kim; Hyo Jeong Oh; Chang-Soo Choi; Dong Han Yeom; Suck Chei Choi

    2008-01-01

    AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique.METHODS: The seventeen patients (7 male and 10 female; mean age 67.8 years) with difficult common bile duct (CBD) stones were not amenable for conventional endoscopic maneuvers such as sphincterotomy and mechanical lithotripsy were included in this study. Laser wavelengths of 532 nm and 1064 nm as a double pulse were applied with pulse energy of 120 mJ. The laser fiber was advanced under fluoroscopic control through the ERCP balloon catheter. Laser lithotripsy was continued until the fragment size seemed to be less than 10 mm.Endoscopic extraction of the stones and fragments was performed with the use of the Dormia basket and balloon catheter.RESULTS: Bile duct clearance was achieved in 15 of 17 patients (88%). The mean number of treatment sessions was 1.7 ± 0.6. Endoscopic stone removal could not be achieved in 2 patients (7%). Adverse effects were noted in three patients (hemobilia, pancreatitis, and cholangitis).CONCLUSION: The Frequency Doubled Double Pulse Nd:YAG (FREDDY) laser may be an effective and safe technique in treatment of difficult bile duct stones.

  5. Translocation frequency of double-stranded DNA through a solid-state nanopore

    CERN Document Server

    Bell, Nicholas A W; Keyser, Ulrich F

    2015-01-01

    Solid-state nanopores are single molecule sensors that measure changes in ionic current as charged polymers such as DNA pass through. Here, we present comprehensive experiments on the length, voltage and salt dependence of the frequency of double-stranded DNA translocations through conical quartz nanopores with mean opening diameter 15 nm. We observe an entropic barrier limited, length dependent translocation frequency at 4M LiCl salt concentration and a drift-dominated, length independent translocation frequency at 1M KCl salt concentration. These observations are described by a unifying convection-diffusion equation which includes the contribution of an entropic barrier for polymer entry.

  6. Frequency Characteristics of Double-Walled Carbon Nanotube Resonator with Different Length

    Directory of Open Access Journals (Sweden)

    Jun-Ha LEE

    2016-05-01

    Full Text Available In this paper, we have conducted classical molecular dynamics simulations for DWCNTs of various wall lengths to investigate their use as ultrahigh frequency nano-mechanical resonators. We sought to determine the variations in the frequency of these resonators according to changes in the DWCNT wall lengths. For a double-walled carbon nanotube resonator with a shorter inner nanotube, the shorter inner nanotube can be considered to be a flexible core, and thus, the length influences the fundamental frequency. In this paper, we analyze the variation in frequency of ultra-high frequency nano-mechnical resonators constructed from DWCNTs with different wall lengths.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12951

  7. Improved automated perimetry performance in elderly subjects after listening to Mozart

    OpenAIRE

    Junia Cabral Marques; Adriana Chaves Oliveira Vanessa; Macedo Batista Fiorelli; Niro Kasahara

    2009-01-01

    PURPOSE: To evaluate the performance of automated perimetry of elderly subjects naïve to AP after listening to a Mozart sonata. INTRODUCTION: Automated perimetry (AP) is a psychophysical test used to assess visual fields in patients with neurological disorders and glaucoma. In a previous study, Fiorelli et al. showed that young subjects who listened to a Mozart sonata prior to undergoing AP performed better in terms of reliability than those who did not listen to the sonata. METHODS: Fifty-tw...

  8. Comparison of Threshold Saccadic Vector Optokinetic Perimetry (SVOP) and Standard Automated Perimetry (SAP) in Glaucoma. Part II: Patterns of Visual Field Loss and Acceptability.

    Science.gov (United States)

    McTrusty, Alice D; Cameron, Lorraine A; Perperidis, Antonios; Brash, Harry M; Tatham, Andrew J; Agarwal, Pankaj K; Murray, Ian C; Fleck, Brian W; Minns, Robert A

    2017-09-01

    We compared patterns of visual field loss detected by standard automated perimetry (SAP) to saccadic vector optokinetic perimetry (SVOP) and examined patient perceptions of each test. A cross-sectional study was done of 58 healthy subjects and 103 with glaucoma who were tested using SAP and two versions of SVOP (v1 and v2). Visual fields from both devices were categorized by masked graders as: 0, normal; 1, paracentral defect; 2, nasal step; 3, arcuate defect; 4, altitudinal; 5, biarcuate; and 6, end-stage field loss. SVOP and SAP classifications were cross-tabulated. Subjects completed a questionnaire on their opinions of each test. We analyzed 142 (v1) and 111 (v2) SVOP and SAP test pairs. SVOP v2 had a sensitivity of 97.7% and specificity of 77.9% for identifying normal versus abnormal visual fields. SAP and SVOP v2 classifications showed complete agreement in 54% of glaucoma patients, with a further 23% disagreeing by one category. On repeat testing, 86% of SVOP v2 classifications agreed with the previous test, compared to 91% of SAP classifications; 71% of subjects preferred SVOP compared to 20% who preferred SAP. Eye-tracking perimetry can be used to obtain threshold visual field sensitivity values in patients with glaucoma and produce maps of visual field defects, with patterns exhibiting close agreement to SAP. Patients preferred eye-tracking perimetry compared to SAP. This first report of threshold eye tracking perimetry shows good agreement with conventional automated perimetry and provides a benchmark for future iterations.

  9. Physiologic statokinetic dissociation is eliminated by equating static and kinetic perimetry testing procedures.

    Science.gov (United States)

    Phu, Jack; Al-Saleem, Noha; Kalloniatis, Michael; Khuu, Sieu K

    2016-11-01

    In the present study, we measured the extent of statokinetic dissociation (SKD) in normal observers and then equated the psychophysical tasks into a two-interval forced choice (2IFC) procedure. In Experiment 1, we used the Humphrey visual field analyzer in static perimetry and automated kinetic perimetry modes to measure contrast sensitivity thresholds and the Goldmann manual kinetic perimeter to measure isopters. This was carried out using a Goldmann size II target. Goldmann kinetic perimetry was performed manually with both inward (peripheral to center) and outward (center to periphery) directions of movement to deduce an "average" isopter. This revealed the presence of SKD when superimposed upon the map of static contrast threshold results. There was no evidence of any contribution of examiner technique or instrument-specific differences to SKD. In Experiment 2, we determined the psychometric curves plotting proportion seen as a function of stimulus eccentricity with static and kinetic stimuli with a 2IFC procedure and method of constant stimuli. In an additional experiment, we also showed that subjects were able to reliably discriminate whether a stimulus was static, moving inward, or moving outward, and hence, comparisons could be made between static and kinetic perimetry tasks. Overall, by making the task objective and reducing criterion bias, eccentricity thresholds were equated across static and kinetic perimetry methods; hence, no evidence of SKD was seen. We suggest SKD is inherent to the differences in methodology of threshold measurement in conventional static and kinetic perimetry and individual criterion bias.

  10. Low-cost, smartphone based frequency doubling technology visual field testing using virtual reality (Conference Presentation)

    Science.gov (United States)

    Alawa, Karam A.; Sayed, Mohamed; Arboleda, Alejandro; Durkee, Heather A.; Aguilar, Mariela C.; Lee, Richard K.

    2017-02-01

    Glaucoma is the leading cause of irreversible blindness worldwide. Due to its wide prevalence, effective screening tools are necessary. The purpose of this project is to design and evaluate a system that enables portable, cost effective, smartphone based visual field screening based on frequency doubling technology. The system is comprised of an Android smartphone to display frequency doubling stimuli and handle processing, a Bluetooth remote for user input, and a virtual reality headset to simulate the exam. The LG Nexus 5 smartphone and BoboVR Z3 virtual reality headset were used for their screen size and lens configuration, respectively. The system is capable of running the C-20, N-30, 24-2, and 30-2 testing patterns. Unlike the existing system, the smartphone FDT tests both eyes concurrently by showing the same background to both eyes but only displaying the stimulus to one eye at a time. Both the Humphrey Zeiss FDT and the smartphone FDT were tested on five subjects without a history of ocular disease with the C-20 testing pattern. The smartphone FDT successfully produced frequency doubling stimuli at the correct spatial and temporal frequency. Subjects could not tell which eye was being tested. All five subjects preferred the smartphone FDT to the Humphrey Zeiss FDT due to comfort and ease of use. The smartphone FDT is a low-cost, portable visual field screening device that can be used as a screening tool for glaucoma.

  11. High-frequency manipulation of few-electron double quantum dots-toward spin qubits

    Science.gov (United States)

    Kodera, T.; van der Wiel, W. G.; Ono, K.; Sasaki, S.; Fujisawa, T.; Tarucha, S.

    2004-04-01

    We use a photon-assisted tunneling (PAT) technique to study the high-frequency response of one- and two-electron states in a semiconductor vertically coupled double-dot system. In particular, PAT associated with two-electron spin states in the spin-blockade regime is observed up to the absorption of 10 photons, indicating the preservation of long relaxation times and hence the robustness of our electron spin device under strong microwave irradiation. An alternative double-dot structure with greater flexibility in tuning the inter-dot coupling is presented and its transport characteristics are discussed. This structure is proposed for high-frequency control of two-electron spin states, as required for quantum computation schemes using electron spins in quantum dots.

  12. Treatment of nevus of OTA by Q-switched, frequency doubled, ND: Yag laser

    Directory of Open Access Journals (Sweden)

    National Skin and Hair Care Centre

    2002-01-01

    Full Text Available Nevus of Ota is a dermal melanocytic nevus for which hitherto no effective therapy was available. Lasers have been successfully tried for ablation. But there is no Indian experience till date. Q- Switched, Frequency Doubled, Nd: YAG Laser was installed at our centre an year ago. The first operated case, which has shown near complete pigment dilution, is being presented. The patient underwent three treatments with a minimum of 2 months between sessions. Pre and post therapy photographs were taken and side effects documented. The patient has shown near complete pigment dilution after 3 treatments. Q-Switched, Frequency Doubled, Nd: YAG Laser is effective in treating Nevus of Ota in the Indian skin types. There are no complications noticed till date in our experience.

  13. Study of fuzzy adaptive PID controller on thermal frequency stabilizing laser with double longitudinal modes

    Science.gov (United States)

    Mo, Qingkai; Zhang, Tao; Yan, Yining

    2016-10-01

    There are contradictions among speediness, anti-disturbance performance, and steady-state accuracy caused by traditional PID controller in the existing light source systems of thermal frequency stabilizing laser with double longitudinal modes. In this paper, a new kind of fuzzy adaptive PID controller was designed by combining fuzzy PID control technology and expert system to make frequency stabilizing system obtain the optimal performance. The experiments show that the frequency stability of the designed PID controller is similar to the existing PID controller (the magnitude of frequency stability is less than 10-9 in constant temperature and 10-7 in open air). But the preheating time is shortened obviously (from 10 minutes to 5 minutes) and the anti-disturbance capability is improved significantly (the recovery time needed after strong interference is reduced from 1 minute to 10 seconds).

  14. Frequency doubled high-power disk lasers in pulsed and continuous-wave operation

    Science.gov (United States)

    Weiler, Sascha; Hangst, Alexander; Stolzenburg, Christian; Zawischa, Ivo; Sutter, Dirk; Killi, Alexander; Kalfhues, Steffen; Kriegshaeuser, Uwe; Holzer, Marco; Havrilla, David

    2012-03-01

    The disk laser with multi-kW output power in infrared cw operation is widely used in today's manufacturing, primarily in the automotive industry. The disk technology combines high power (average and/or peak power), excellent beam quality, high efficiency and high reliability with low investment and operating costs. Additionally, the disk laser is ideally suited for frequency conversion due to its polarized output with negligible depolarization losses. Laser light in the green spectral range (~515 nm) can be created with a nonlinear crystal. Pulsed disk lasers with green output of well above 50 W (extracavity doubling) in the ps regime and several hundreds of Watts in the ns regime with intracavity doubling are already commercially available whereas intracavity doubled disk lasers in continuous wave operation with greater than 250 W output are in test phase. In both operating modes (pulsed and cw) the frequency doubled disk laser offers advantages in existing and new applications. Copper welding for example is said to show much higher process reliability with green laser light due to its higher absorption in comparison to the infrared. This improvement has the potential to be very beneficial for the automotive industry's move to electrical vehicles which requires reliable high-volume welding of copper as a major task for electro motors, batteries, etc.

  15. Topological charge transfer in frequency doubling of fractional orbital angular momentum state

    Science.gov (United States)

    Ni, R.; Niu, Y. F.; Du, L.; Hu, X. P.; Zhang, Y.; Zhu, S. N.

    2016-10-01

    Nonlinear frequency conversion is promising for manipulating photons with orbital angular momentum (OAM). In this letter, we investigate the second harmonic generation (SHG) of light beams carrying fractional OAM. By measuring the OAM components of the generated second harmonic (SH) waves, we find that the integer components of the fundamental beam will interact with each other during the nonlinear optical process; thus, we figure out the law for topological charge transfer in frequency doubling of the fractional OAM state. Theoretical predictions by solving the nonlinear coupled wave equations are consistent with the experimental results.

  16. A K-Band Push-Push VCO MMIC using embedded frequency doubling mechanism

    OpenAIRE

    Sim, Sang-Hoon; Ko, Sangsoo; Hong, Songcheol

    2004-01-01

    A K-Band Push-Push VCO MMIC which has small size, high output power and low phase noise is presented. This push-push VCO utilize the embedded frequency doubling mechanism of cross coupled topology. A commercial InGaP/GaAs HBT technology with the f T of 60 GHz and the fMAX of 110 GHz was used for the implementation. The oscillation frequency is from 21.02 GHz to 21.17 GHz. The peak output power of the VCO is 1.7dBm. The phase noise is -110dBc/Hz at 1MHz offset from 2...

  17. Evaluation of magnocellular pathway abnormalities in schizophrenia: a frequency doubling technology study and clinical implications

    Directory of Open Access Journals (Sweden)

    Fabiana Benites Vaz de Lima

    2013-04-01

    Full Text Available BACKGROUND: Visual processing deficits have been reported for patients with schizophrenia. Previous studies demonstrated differences in early-stage processing of schizophrenics, although the nature, extent, and localization of the disturbance are unknown. The magnocellular and parvocellular visual pathways are associated with transient and sustained channels, but their respective contributions to schizophrenia-related visual deficits remains controversial. PURPOSE: The aim of this study was to evaluate magnocellular dysfunction in schizophrenia using frequency doubling technology. METHODS: Thirty-one patients with schizophrenia and 34 healthy volunteers were examined. Frequency doubling technology testing was performed in one session, consisting of a 15-minute screening strategy followed by the C-20 program for frequency doubling technology. RESULTS: Schizophrenic patients showed lower global mean sensitivity (30,97 ± 2,25 dB compared with controls (32,17 ± 3,08 dB, p<0.009. Although there was no difference in the delta sensitivity of hemispheres, there was a difference in sensitivity analysis of the fibers crossing the optic chiasm, with lower mean sensitivity in the patient group (28,80 dB versus controls (30,66 dB. The difference was higher in fibers that do not cross the optic chiasm, with lower mean sensitivity in patients (27,61 dB versus controls (30,26 dB, p<0.005. CONCLUSIONS: Our results suggest that there are differences between global sensitivity and fiber sensitivity measured by frequency doubling technology. The different sensitivity of fibers that do not cross the optic chiasm is consistent with most current etiological hypotheses for schizophrenia. The decreased sensitivity responses in the optic radiations may significantly contribute to research assessing early-stage visual processing deficits for patients with schizophrenia.

  18. Dynamics of two coupled chaotic multimode Nd:YAG lasers with intracavity frequency doubling crystal

    Indian Academy of Sciences (India)

    Thomas Kuruvilla; V M Nandakumaran

    2000-03-01

    The effect of coupling two chaotic Nd:YAG lasers with intracavity KTP crystal for frequency doubling is numerically studied for the case of the laser operating in three longitudinal modes. It is seen that the system goes from chaotic to periodic and then to steady state as the coupling constant is increased. The intensity time series and phase diagrams are drawn and the Lyapunov characteristic exponent is calculated to characterize the chaotic and periodic regions.

  19. Ultrahigh contrast from a frequency-doubled chirped-pulse-amplification beamline.

    Science.gov (United States)

    Hillier, David; Danson, Colin; Duffield, Stuart; Egan, David; Elsmere, Stephen; Girling, Mark; Harvey, Ewan; Hopps, Nicholas; Norman, Michael; Parker, Stefan; Treadwell, Paul; Winter, David; Bett, Thomas

    2013-06-20

    This paper describes frequency-doubled operation of a high-energy chirped-pulse-amplification beamline. Efficient type-I second-harmonic generation was achieved using a 3 mm thick 320 mm aperture KDP crystal. Shots were fired at a range of energies achieving more than 100 J in a subpicosecond, 527 nm laser pulse with a power contrast of 10(14).

  20. A Micro Blue-violet Laser by Frequency Doubling of Semiconductor Laser

    Institute of Scientific and Technical Information of China (English)

    周寿桓; 姜东升; 赵鸿

    2001-01-01

    In this paper, a micro blue-violet laser by frequency doubling of a semiconductor laser with a new nonlinear organometallic complex cadmium mercury thiocyanate crystal (CMTC) is reported. At room temperature, the blue-violet laser output of 11.8 mW at 404 nm and the conversion4efficiency of the second harmonic generation (SHG) of 0. 60% were obtained with a 1. 98 W, 808 nm semiconductor laser and a 4 mm crystal.

  1. Effects of fabricated error on transmission performance of double layer frequency selective surface configuration

    Institute of Scientific and Technical Information of China (English)

    HE Bin; SUN Lian-chun

    2005-01-01

    Based on the experimental results, in which the fabricated error of the double layer frequency selective surface (FSS) leads to the transmission loss and the resonant frequency leaves away the design resonant frequency, the inter-layer separation distance (ISD) and the unit cell aligning error (UAE) were used as main variables to study the transmission performance attenuation of the double layer FSS configuration. The numerical analysis model for ISD and UAE was established and also was used to simulate the ring unit cell FSS transmission performance by the finite element and periodic moment methods. The double layer ring aperture FSS configuration designed was used as the numerical model. As a result of the numerical analysis, it is shown that both ISD and UAE produce insertion transmission loss (ITL) and insertion phase distortion (IPD) directly. Furthermore, ISD results in more loss of the amplitude of the transmitted signal for the FSS than UAE. It is significant for the designer of the multiplayer FSS to assign the fabricated error of the FSS dielectric layers. The UAE introduces the insertion phase variation badly.

  2. The relationship between temporal phase discrimination ability and the frequency doubling illusion.

    Science.gov (United States)

    Vallam, Kunjam; Metha, Andrew B

    2007-12-20

    The frequency doubling illusion (FDI) occurs when a low spatial frequency sinusoidal grating is modulated at high temporal frequencies--its apparent spatial frequency increases. A recent study suggests that this illusion is perceived due to a frequency-dependent loss of temporal phase encoding ability. We sought to elucidate the relationship between temporal phase encoding and the FDI by exploring the spatiotemporal characteristics of temporal phase discrimination (TPD) thresholds using a novel stimulus comprising three grating patches presented simultaneously in a triangular pattern. A reference grating was presented superiorly, and six degrees below two gratings (one a copy of the reference) were each randomly presented in one of two fixed positions. The odd grating had abutting regions of spatial half-cycles with alternate half-cycles locked in temporal phase. The temporal phase difference between adjoining half-cycles was varied between 0 degrees and 180 degrees via QUEST staircase--subjects had to identify which lower stimulus appeared different from the reference grating. TPD thresholds were measured for 0.25, 0.50, and 2.20 cpd stimulus at six temporal frequencies (1 to 28 Hz) at 2x, 4x, and 8x orientation identification contrast thresholds. For all subjects, thresholds were variable at low contrasts. At higher contrasts, TPD thresholds increase for 0.25 and 0.50 cpd gratings with increasing flicker rate. These data support the idea that frequency-dependent loss of temporal phase encoding ability could possibly underlie the FDI.

  3. Efficient generation of 3.5 W laser light at 515 nm by frequency doubling a single-frequency high power DBR tapered diode laser

    Science.gov (United States)

    Jensen, Ole Bjarlin; Hansen, Anders Kragh; Müller, André; Sumpf, Bernd; Petersen, Paul Michael; Andersen, Peter E.

    2017-06-01

    More than 3.5 W of green light at 515 nm is generated by frequency doubling a single-frequency high power DBR tapered diode laser. The frequency doubling is performed in a cascade of PPMgLN and PPMgSLT crystals in order to reach high power and avoid thermal effects present in PPMgLN at high power. The green light is diffraction limited (M2 <1.1) and single-frequency operation is demonstrated with a linewidth less than 2 pm.

  4. The Effect of Cataract on Eye Movement Perimetry

    Directory of Open Access Journals (Sweden)

    G. Thepass

    2015-01-01

    Full Text Available Purpose. To determine how different grades of cataract affect sensitivity threshold and saccadic reaction time (SRT in eye movement perimetry (EMP. Methods. In EMP, the visual field is tested by assessing the saccades that a subject makes towards peripheral stimuli using an eye tracker. Forty-eight cataract patients underwent pre- and postoperative EMP examination in both eyes. The subjects had to fix a central stimulus presented on the eye tracker monitor and to look at any detected peripheral stimulus upon its appearance. A multilevel mixed model was used to determine the factors that affected the sensitivity threshold and the SRT as a function of cataract grade. Results. We found no effect of cataract severity (LOCS III grades I through IV on SRT and the sensitivity thresholds. In cataract of LOCS III grade V, however, we found an increase by 27% and 21% (p<0.001, respectively, compared to the SRT and the sensitivity threshold in LOCS III grade I. Eyes that underwent cataract surgery showed no change in mean SRTs and sensitivity thresholds after surgery in LOCS III grade IV and lower. Conclusion. The present study shows that EMP can be readily used in patients with cataract with LOCS III grade IV and below.

  5. High-efficiency frequency doubling of continuous-wave laser light

    CERN Document Server

    Ast, Stefan; Schönbeck, Axel; Lastzka, Nico; Steinlechner, Jessica; Eberle, Tobias; Mehmet, Moritz; Steinlechner, Sebastian; Schnabel, Roman

    2011-01-01

    We report on the observation of high efficiency frequency doubling of 1550 nm continuous-wave laser light in a nonlinear cavity containing a periodically poled potassium titanyl phosphate crystal (PPKTP). The fundamental field had a power of 1.10 W and was converted into 1.05 W at 775 nm, yielding a total external conversion efficiency of (95 \\pm 1)%. The latter value is based on the measured depletion of the fundamental field being consistent with the absolute values derived from numerical simulations. According to our model, the conversion efficiency achieved was limited by the non-perfect mode-matching into the nonlinear cavity and the pump power available. Our result shows that cavity-assisted frequency conversion based on PPKTP is well suited for low-decoherence frequency conversion of quantum states of light.

  6. Improved automated perimetry performance in elderly subjects after listening to Mozart

    Directory of Open Access Journals (Sweden)

    Junia Cabral Marques

    2009-01-01

    Full Text Available PURPOSE: To evaluate the performance of automated perimetry of elderly subjects naïve to AP after listening to a Mozart sonata. INTRODUCTION: Automated perimetry (AP is a psychophysical test used to assess visual fields in patients with neurological disorders and glaucoma. In a previous study, Fiorelli et al. showed that young subjects who listened to a Mozart sonata prior to undergoing AP performed better in terms of reliability than those who did not listen to the sonata. METHODS: Fifty-two AP-naïve, normal subjects underwent Automated perimetry (SITA 24-2. The study group (25 subjects underwent AP after listening to Mozart's Sonata for Two Pianos in D Major, and the control group (27 subjects underwent Automated perimetry without prior exposure to the music. RESULTS: The study group had significantly lower false negative rates and a lower visual field reliability score than the controls (P=0.04 and P=0.04, respectively. The test time was shorter for the study group (P=0.03. DISCUSSION: This study shows that elderly subjects, when exposed to the Mozart sonata immediately before AP testing, have lower false negative rates and lower visual field reliability scores when compared with an age- and gender-matched control group. Our results differ from those of Fiorelli et al. who found lower false positive rates and less fixation loss in addition to lower false negative rates. CONCLUSION: Listening to a Mozart sonata seems to improve automated perimetry reliability in elderly subjects.

  7. Chromatic-achromatic perimetry in four clinic cases: Glaucoma and diabetes

    Directory of Open Access Journals (Sweden)

    Inmaculada Cabezos

    2015-01-01

    Full Text Available Background: Some diseases that affect the visual system may show loss of chromatic-achromatic sensitivity before obvious physical signs appear in the usual examination of the eye′s posterior segment. A perimetric study has been conducted with four typical patients with glaucoma and diabetes, at different stages of the disease. Materials and Methods: In addition to the standard white-on-white (standard automated perimetry [SAP], a test battery has been used to study patient′s contrast sensitivity, using stimuli with different chromatic, spatial, and temporal content (multichannel perimetry. The choice of stimuli tries to maximize the response of different visual mechanisms: Achromatic (parvocellular and magnocellular origin; chromatic red-green (parvocellular origin; and chromatic blue-yellow (koniocellular origin. Results: The results seem to indicate losses in the achromatic-parvocellular perimetry and both chromatic perimetry tests, undetected by conventional SAP. Conclusions: Our results illustrate that our patients without visible retinal alterations show signs of suspicion in multichannel perimetry.

  8. Improved automated perimetry performance in elderly subjects after listening to Mozart.

    Science.gov (United States)

    Marques, Junia Cabral; Vanessa, Adriana Chaves Oliveira; Fiorelli, Macedo Batista; Kasahara, Niro

    2009-01-01

    To evaluate the performance of automated perimetry of elderly subjects naïve to AP after listening to a Mozart sonata. Automated perimetry (AP) is a psychophysical test used to assess visual fields in patients with neurological disorders and glaucoma. In a previous study, Fiorelli et al. showed that young subjects who listened to a Mozart sonata prior to undergoing AP performed better in terms of reliability than those who did not listen to the sonata. Fifty-two AP-naïve, normal subjects underwent Automated perimetry (SITA 24-2). The study group (25 subjects) underwent AP after listening to Mozart's Sonata for Two Pianos in D Major, and the control group (27 subjects) underwent Automated perimetry without prior exposure to the music. The study group had significantly lower false negative rates and a lower visual field reliability score than the controls (P=0.04 and P=0.04, respectively). The test time was shorter for the study group (P=0.03). This study shows that elderly subjects, when exposed to the Mozart sonata immediately before AP testing, have lower false negative rates and lower visual field reliability scores when compared with an age- and gender-matched control group. Our results differ from those of Fiorelli et al. who found lower false positive rates and less fixation loss in addition to lower false negative rates. Listening to a Mozart sonata seems to improve automated perimetry reliability in elderly subjects.

  9. In-field frequencies and characteristics of oilseed rape with double herbicide resistance.

    Science.gov (United States)

    Dietz-Pfeilstetter, Antje; Zwerger, Peter

    2009-01-01

    When growing different transgenic herbicide-resistant oilseed rape cultivars side by side, seeds with multiple herbicide resistance can arise, possibly causing problems for the management of volunteer plants. Large-scale field experiments were performed in the years 1999/2000 and 2000/2001 in order to investigate the frequencies and the consequences of the transfer of herbicide resistance genes from transgenic oilseed rape to cultivars grown on neighboring agricultural fields. Transgenic oilseed rape with resistance to glufosinate-ammonium (LibertyLink, LL) and with glyphosate resistance (RoundupReady, RR), respectively, was sown in adjacent 0.5 ha plots, surrounded by about 8 ha non-transgenic oilseed rape. The plots and the field were either in direct contact (0.5 m gap width) or they were separated by 10 m of fallow land. Seed samples taken during harvest in the transgenic plots at different distances were investigated for progeny with resistance to the respective other herbicide. It was found that outcrossing frequencies were reduced to different extents by a 10 m isolation distance. In addition to pollen-mediated transgene flow as a result of outcrossing, we found considerable seed-mediated gene flow by adventitious dispersal of transgenic seeds through the harvesting machine. Volunteer plants with double herbicide resistance emerging in the transgenic plots after harvest were selected by suitable applications of the complementary herbicides Basta and Roundup Ultra. In both years, double-resistant volunteers were largely restricted to the inner edges of the plots. Expression analysis under controlled laboratory conditions of double-resistant plants generated by manual crosses revealed stability of transgene expression even at elevated temperatures. Greenhouse tests with double-resistant oilseed rape plants gave no indication that the sensitivity to a range of different herbicides is changed as compared to non-transgenic oilseed rape.

  10. Frequency locking to a high-finesse Fabry-Perot cavity of a Frequency doubled Nd YAG laser used as the optical phase modulator

    CERN Document Server

    Bregant, M; Valle, F D; Ruoso, G; Zavattini, G

    2002-01-01

    We report on the frequency locking of a frequency doubled Nd:YAG laser to a 45 000 finesse, 87-cm-long, Fabry-Perot cavity using a modified form of the Pound-Drever-Hall technique. Necessary signals, such as light phase modulation and frequency correction feedback, are fed direcly to the infrared pump laser. This is sufficient to achieve a stable locking of the 532 nm visible beam to the cavity, also showing that the doubling process does not degrade laser performances.

  11. High power frequency doubled GaInNAs semiconductor disk laser emitting at 615 nm.

    Science.gov (United States)

    Härkönen, Antti; Rautiainen, Jussi; Guina, Mircea; Konttinen, Janne; Tuomisto, Pietari; Orsila, Lasse; Pessa, Markus; Okhotnikov, Oleg G

    2007-03-19

    We report on an optically-pumped intracavity frequency doubled GaInNAs/GaAs -based semiconductor disk laser emitting around 615 nm. The laser operates at fundamental wavelength of 1230 nm and incorporates a BBO crystal for light conversion to the red wavelength. Maximum output power of 172 mW at 615 nm was achieved from a single output. Combined power from two outputs was 320 mW. The wavelength of visible emission could be tuned by 4.5 nm using a thin glass etalon inside the cavity.

  12. Ultra low frequency waves observed by Double Star TC-1 in the plasmasphere boundary layer

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The characteristic and properties of ULF waves in the plasmasphere boundary layer during two very quiet periods are present. The ULF waves were detected by Double Star TC-1 when the spacecraft passed through the plasmasphere in an outbound and inbound trajectories, respectively. A clear association between the ULF waves and periodic variations of energetic ions fluxes was observed. The ob-servations showed that the wave frequency was higher inside the plasmasphere than outside. The mechanism generating these ULF waves and possible diagnos-ing of the "classical plasmapause" location with the ULF wave were discussed.

  13. Temporal structure of double plasma frequency emission of thin beam-heated plasma

    Energy Technology Data Exchange (ETDEWEB)

    Postupaev, V. V.; Ivanov, I. A.; Arzhannikov, A. V.; Vyacheslavov, L. N. [Budker Institute of Nuclear Physics, 11 Lavrentjev Avenue, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 2 Pirogova st., 630090 Novosibirsk (Russian Federation); Burdakov, A. V.; Polosatkin, S. V. [Budker Institute of Nuclear Physics, 11 Lavrentjev Avenue, 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 20 Karl Marks Avenue, 630092 Novosibirsk (Russian Federation); Sklyarov, V. F.; Gavrilenko, D. Ye.; Kandaurov, I. V.; Kurkuchekov, V. V.; Mekler, K. I.; Popov, S. S.; Rovenskikh, A. F.; Sudnikov, A. V.; Sulyaev, Yu. S.; Trunev, Yu. A. [Budker Institute of Nuclear Physics, 11 Lavrentjev Avenue, 630090 Novosibirsk (Russian Federation); Kasatov, A. A. [Novosibirsk State University, 2 Pirogova st., 630090 Novosibirsk (Russian Federation)

    2013-09-15

    In the work presented here dynamics of spiky microwave emission of a beam-heated plasma near the double plasma frequency in ∼100 GHz band was studied. The plasma is heated by 80 keV, ∼2 MW, sub-ms electron beam that is injected into the multiple-mirror trap GOL-3. The beam-heated plasma diameter is of the order of the emitted wavelength. Modulation of individual emission spikes in the microwave radiation is found. The radiation dynamics observed can be attributed to a small number of compact emitting zones that are periodically distorted.

  14. All-solid-state ultraviolet laser based on frequency doubling in an external ring cavity

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An all-solid-state ultraviolet laser based on frequency doubling in an external ring cavity with low input pump power is reported. Both second harmonic generation (SHG) and fourth harmonic generation (FHG) occurred in an external threemirrors ring cavity. The need for impedance matching of this cavity to the input radiation was eliminated and the cavity adaptation was simplified, because the mirrors were not highly reflecting at 1064 nm and the cavity resonates only at 532 nm. Experiment results demonstrate that the conversion efficiency of this external cavity is higher than that of the singlepass condition.

  15. Green frequency-doubled laser-beam propagation in high-temperature hohlraum plasmas.

    Science.gov (United States)

    Niemann, C; Berger, R L; Divol, L; Froula, D H; Jones, O; Kirkwood, R K; Meezan, N; Moody, J D; Ross, J; Sorce, C; Suter, L J; Glenzer, S H

    2008-02-01

    We demonstrate propagation and small backscatter losses of a frequency-doubled (2omega) laser beam interacting with inertial confinement fusion hohlraum plasmas. The electron temperature of 3.3 keV, approximately a factor of 2 higher than achieved in previous experiments with open geometry targets, approaches plasma conditions of high-fusion yield hohlraums. In this new temperature regime, we measure 2omega laser-beam transmission approaching 80% with simultaneous backscattering losses of less than 10%. These findings suggest that good laser coupling into fusion hohlraums using 2omega light is possible.

  16. Frequency-doubled telecom fiber laser for a cold atom interferometer using optical lattices

    Science.gov (United States)

    Theron, Fabien; Bidel, Yannick; Dieu, Emily; Zahzam, Nassim; Cadoret, Malo; Bresson, Alexandre

    2017-06-01

    A compact and robust frequency-doubled telecom laser system at 780 nm is presented for a rubidium cold atom interferometer using optical lattices. Adopting an optical switch at 1.5 μm and a dual-wavelength second harmonic generation system, only one laser amplifier is required for the laser system. Our system delivers a 900 mW laser beam with a detuning of 110 GHz for the optical lattice and a 650 mW laser beam with an adjustable detuning between 0 and -1 GHz for the laser cooling, the detection and the Raman transitions.

  17. Frequency doubled telecom fiber laser for a cold atom interferometer using optical lattices

    CERN Document Server

    Theron, Fabien; Dieu, Emily; Zahzam, Nassim; Cadoret, Malo; Zahzam, Nassim; Bresson, Alexandre

    2016-01-01

    A compact and robust laser system, based on a frequency-doubled telecom laser, providing all the lasers needed for a rubidium cold atom interferometer using optical lattices is presented. Thanks to an optical switch at 1.5 \\mu m and a dual-wavelength second harmonic generation system, only one laser amplifier is needed for all the laser system. Our system delivers at 780 nm a power of 900 mW with a detuning of 110 GHz for the optical lattice and a power of 650 mW with an adjustable detuning between 0 and -1 GHz for the laser cooling, the detection and the Raman transitions.

  18. Correcting LCD luminance non-uniformity for threshold Saccadic Vector Optokinetic Perimetry (SVOP).

    Science.gov (United States)

    Perperidis, Antonios; Murray, Ian; Brash, Harry; McTrusty, Alice; Cameron, Lorraine; Fleck, Brian; Minns, Robert

    2013-01-01

    The accurate assessment of visual field function can provide valuable information on a range of visual disorders. Saccadic Vector Optokinetic Perimetry (SVOP) is a novel instrument for measuring supra-threshold visual fields in young children who are otherwise unable to perform Automated Static Perimetry (ASP). However, limitations in Liquid Crystal Display (LCD) technology restrict the ability of SVOP to determine threshold values at various points in the visual field, often required in detailed perimetry examinations. This paper introduces a purpose-specific LCD luminance non-uniformity compensation approach to address this limitation. Thorough quantitative evaluation identifies the effectiveness of the proposed approach in (i) compensating for luminance non-uniformities across an LCD, and (ii) enabling SVOP to perform accurate and precise threshold visual field tests. The findings demonstrate that SVOP provides a promising alternative to the current threshold ASP standard (Humphrey Field Analyser).

  19. A double tuned rail damper—increased damping at the two first pinned-pinned frequencies

    Science.gov (United States)

    Maes, J.; Sol, H.

    2003-10-01

    Railway-induced vibrations are a growing matter of environmental concern. The rapid development of transportation, the increase of vehicle speeds and vehicle weights have resulted in higher vibration levels. In the meantime vibrations that were tolerated in the past are now considered to be a nuisance. Numerous solutions have been proposed to remedy these problems. The majority only acts on a specific part of the dynamic behaviour of the track. This paper presents a possible solution to reduce the noise generated by the 'pinned-pinned' frequencies. Pinned-pinned frequencies correspond with standing waves whose nodes are positioned exactly at the sleeper supports. The two first pinned-pinned frequencies are situated approximately at 950 and 2200 Hz (UIC60-rail and sleeper spacing of 0.60 m). To attenuate these vibrations, the Department of MEMC at the VUB has developed a dynamic vibration absorber called the Double Tuned Rail Damper (DTRD). The DTRD is mounted between two sleepers on the rail and is powered by the motion of the rail. The DTRD consists of two major parts: a steel plate which is connected to the rail with an interface of an elastic layer, and a rubber mass. The two first resonance frequencies of the steel plate coincide with the targeted pinned-pinned frequencies of the rail. The rubber mass acts as a motion controller and energy absorber. Measurements at a test track of the French railway company (SNCF) have shown considerable attenuation of the envisaged pinned-pinned frequencies. The attenuation rate surpasses 5 dB/m at certain frequency bands.

  20. Double-wavelet approach to study frequency and amplitude modulation in renal autoregulation

    DEFF Research Database (Denmark)

    Sosnovtseva, Olga; Pavlov, A N; Mosekilde, E;

    2004-01-01

    Biological time series often display complex oscillations with several interacting rhythmic components. Renal autoregulation, for instance, involves at least two separate mechanisms both of which can produce oscillatory variations in the pressures and flows of the individual nephrons. Using double......-wavelet analysis we propose a method to examine how the instantaneous frequency and amplitude of a fast mode is modulated by the presence of a slower mode. Our method is applied both to experimental data from normotensive and hypertensive rats showing different oscillatory patterns and to simulation results...... obtained from a physiologically based model of the nephron pressure and flow control. We reveal a nonlinear interaction between the two mechanisms that regulate the renal blood flow in the form of frequency and amplitude modulation of the myogenic oscillations....

  1. Compact two wavelength Brillouin fiber laser sensor with double Brillouin frequency spacing

    Science.gov (United States)

    Liu, Yi; Zhang, Mingjiang; Zhang, Jianzhong; Han, Hong; Yi, Xiaogang; Zhang, Jianguo; Wang, Yuncai

    2016-12-01

    A compact two wavelength Brillouin fiber laser (BFL) sensor with double Brillouin frequency spacing is proposed and demonstrated. In the experiment, 20 m polarization maintaining fiber is used as the sensing element and Brillouin gain medium. This short cavity configuration not only guarantees single longitudinal mode operation of two Stokes wavelengths, but also can effectively reduce external perturbations, complexity and noise of BFL in the absence of an erbium-doped fiber amplifier in intra-cavity. In experiment, about 2 MHz/°C sensitivity of beat frequency between the pump and the 2nd-order Stokes wavelength keep in good agreement with the theoretical value. Meanwhile, 0.2 °C temperature stability and  ±0.1 dB power fluctuation are better than the traditional structure. The system is simple and stable, making it convenient for more applications.

  2. Study of Optimal Perimetric Testing in Children (OPTIC: Feasibility, Reliability and Repeatability of Perimetry in Children.

    Directory of Open Access Journals (Sweden)

    Dipesh E Patel

    Full Text Available To investigate feasibility, reliability and repeatability of perimetry in children.A prospective, observational study recruiting 154 children aged 5-15 years, without an ophthalmic condition that affects the visual field (controls, identified consecutively between May 2012 and November 2013 from hospital eye clinics. Perimetry was undertaken in a single sitting, with standardised protocols, in a randomised order using the Humphrey static (SITA 24-2 FAST, Goldmann and Octopus kinetic perimeters. Data collected included test duration, subjective experience and test quality (incorporating examiner ratings on comprehension of instructions, fatigue, response to visual and auditory stimuli, concentration and co-operation to assess feasibility and reliability. Testing was repeated within 6 months to assess repeatability.Overall feasibility was very high (Goldmann=96.1%, Octopus=89% and Humphrey=100% completed the tests. Examiner rated reliability was 'good' in 125 (81.2% children for Goldmann, 100 (64.9% for Octopus and 98 (63.6% for Humphrey perimetry. Goldmann perimetry was the most reliable method in children under 9 years of age. Reliability improved with increasing age (multinomial logistic regression (Goldmann, Octopus and Humphrey, p<0.001. No significant differences were found for any of the three test strategies when examining initial and follow-up data outputs (Bland-Altman plots, n=43, suggesting good test repeatability, although the sample size may preclude detection of a small learning effect.Feasibility and reliability of formal perimetry in children improves with age. By the age of 9 years, all the strategies used here were highly feasible and reliable. Clinical assessment of the visual field is achievable in children as young as 5 years, and should be considered where visual field loss is suspected. Since Goldmann perimetry is the most effective strategy in children aged 5-8 years and this perimeter is no longer available, further

  3. Doubling of coastal flooding frequency within decades due to sea-level rise.

    Science.gov (United States)

    Vitousek, Sean; Barnard, Patrick L; Fletcher, Charles H; Frazer, Neil; Erikson, Li; Storlazzi, Curt D

    2017-05-18

    Global climate change drives sea-level rise, increasing the frequency of coastal flooding. In most coastal regions, the amount of sea-level rise occurring over years to decades is significantly smaller than normal ocean-level fluctuations caused by tides, waves, and storm surge. However, even gradual sea-level rise can rapidly increase the frequency and severity of coastal flooding. So far, global-scale estimates of increased coastal flooding due to sea-level rise have not considered elevated water levels due to waves, and thus underestimate the potential impact. Here we use extreme value theory to combine sea-level projections with wave, tide, and storm surge models to estimate increases in coastal flooding on a continuous global scale. We find that regions with limited water-level variability, i.e., short-tailed flood-level distributions, located mainly in the Tropics, will experience the largest increases in flooding frequency. The 10 to 20 cm of sea-level rise expected no later than 2050 will more than double the frequency of extreme water-level events in the Tropics, impairing the developing economies of equatorial coastal cities and the habitability of low-lying Pacific island nations.

  4. The Double Pulsar Eclipses I: Phenomenology and Multi-frequency Analysis

    CERN Document Server

    Breton, R P; McLaughlin, M A; Lyutikov, M; Kramer, M; Stairs, I H; Ransom, S M; Ferdman, R D; Camilo, F; Possenti, A

    2012-01-01

    The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to probe directly the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al., and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor (~ 10^5). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confin...

  5. Doubling of coastal flooding frequency within decades due to sea-level rise

    Science.gov (United States)

    Vitousek, Sean; Barnard, Patrick L.; Fletcher, Charles H.; Frazer, Neil; Erikson, Li; Storlazzi, Curt D.

    2017-01-01

    Global climate change drives sea-level rise, increasing the frequency of coastal flooding. In most coastal regions, the amount of sea-level rise occurring over years to decades is significantly smaller than normal ocean-level fluctuations caused by tides, waves, and storm surge. However, even gradual sea-level rise can rapidly increase the frequency and severity of coastal flooding. So far, global-scale estimates of increased coastal flooding due to sea-level rise have not considered elevated water levels due to waves, and thus underestimate the potential impact. Here we use extreme value theory to combine sea-level projections with wave, tide, and storm surge models to estimate increases in coastal flooding on a continuous global scale. We find that regions with limited water-level variability, i.e., short-tailed flood-level distributions, located mainly in the Tropics, will experience the largest increases in flooding frequency. The 10 to 20 cm of sea-level rise expected no later than 2050 will more than double the frequency of extreme water-level events in the Tropics, impairing the developing economies of equatorial coastal cities and the habitability of low-lying Pacific island nations.

  6. Effect of aspherical and yellow tinted intraocular lens on blue-on-yellow perimetry Efeito das lentes intraoculares asféricas e com pigmentação amarela na campimetria azul-amarelo

    Directory of Open Access Journals (Sweden)

    Rodrigo França de Espíndola

    2012-10-01

    Full Text Available PURPOSE: To investigate the possible effect of aspherical or yellow tinted intraocular lens (IOL on contrast sensitivity and blue-on-yellow perimetry. METHODS: This prospective randomized bilateral double-masked clinical study included 52 patients with visually significant bilateral cataracts divided in two groups; 25 patients (50 eyes received aspherical intraocular lens in one eye and spherical intraocular lens in the fellow eye; and 27 patients (54 eyes received ultraviolet and blue light filter (yellow tinted IOL implantation in one eye and acrylic ultraviolet filter IOL in the fellow eye. The primary outcome measures were contrast sensitivity and blue-on-yellow perimetry values (mean deviation [MD] and pattern standard deviation [PSD] investigated two years after surgery. The results were compared intra-individually. RESULTS: There was a statistically significant between-group (aspherical and spherical intraocular lens difference in contrast sensitivity under photopic conditions at 12 cycles per degree and under mesopic conditions at all spatial frequencies. There were no between-group significant differences (yellow tinted and clear intraocular lens under photopic or mesopic conditions. There was no statistically significant difference between all intraocular lens in MD or PSD. CONCLUSION: Contrast sensitivity was better under mesopic conditions with aspherical intraocular lens. Blue-on-yellow perimetry did not appear to be affected by aspherical or yellow tinted intraocular lens. Further studies with a larger sample should be carried out to confirm or not that hypotheses.OBJETIVO: Investigar a possibilidade de efeitos na sensibilidade ao contraste e nos resultados da campimetria azul-amarelo com implante de uma lente intraocular (LIO asférica ou de pigmentação amarela. MÉTODOS: Trata-se de um estudo prospectivo, randomizado, duplo-mascarado, envolvendo 52 pacientes portadores de catarata senil bilateral, divididos em dois grupos; 25

  7. THE DOUBLE PULSAR ECLIPSES. I. PHENOMENOLOGY AND MULTI-FREQUENCY ANALYSIS

    Energy Technology Data Exchange (ETDEWEB)

    Breton, R. P. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Kaspi, V. M. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Lyutikov, M. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Kramer, M. [Max Planck Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Ransom, S. M. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Ferdman, R. D. [University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester, M13 9PL (United Kingdom); Camilo, F. [Columbia University, New York, NY 10027 (United States); Possenti, A., E-mail: breton@astro.utoronto.ca [INAF-Osservatorio Astronomico di Cagliari, Poggio dei Pini, strada 54, I-09012 Capoterra (Italy)

    2012-03-10

    The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to directly probe the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al. and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor ({approx}10{sup 5}). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confinement of the absorbing plasma in the dipolar magnetic field of pulsar B as suggested by Lyutikov and Thompson and such a geometric connection explains that the observed periodicity is harmonically related to pulsar B's spin frequency. We observe that the eclipses require a sharp transition region beyond which the plasma density drops off abruptly. Such a region defines a plasmasphere that would be well inside the magnetospheric boundary of an undisturbed pulsar. It is also two times smaller than the expected standoff radius calculated using the balance of the wind pressure from pulsar A and the nominally estimated magnetic pressure of pulsar B.

  8. Tolerance of low-frequency ultrasound sonophoresis: a double-blind randomized study on humans.

    Science.gov (United States)

    Maruani, Annabel; Vierron, Emilie; Machet, Laurent; Giraudeau, Bruno; Halimi, Jean-Michel; Boucaud, Alain

    2012-05-01

    Sonophoresis [low-frequency ultrasound (US)] has been used in animals and in vitro to investigate enhanced percutaneous absorption of drugs. No study focused on its clinical human tolerance has been published as yet. We aimed to assess the bioeffects of low-frequency US in vivo on human skin in a double-blind randomized-controlled study. We applied pulse-mode US at 36 kHz for 5 min in a step procedure of increasing dosage, from 1.57 to 3.50 W/cm(2), and placebo. The primary outcome was toxic effects of the procedure, defined as a pain score >40 on a 0-100 mm visual analogue scale or necrosis. Erythema (scored from 0 to 3 in severity) was also evaluated. The secondary outcomes were measurements of skin thickness by high-resolution skin imaging, of skin capacitance and temperature. We included 34 healthy volunteers. We found no pain score >38 and no skin necrosis with either US or placebo. Erythema was systematically observed immediately after US application, but after 1 day, we observed three cases in the knee group. The most frequent adverse effect was tinnitus. We observed no marked increase in temperature or cutaneous thickness after US or placebo. Cutaneous capacitance increased immediately after both applications. Such data demonstrating good tolerance of sonophoresis can be useful before the initiation of a clinical trial of the therapeutic use of low-frequency sonophoresis in humans. © 2011 John Wiley & Sons A/S.

  9. A Comparative Evaluation of Humphrey Perimetry and the Multi-channel Pattern Visual Evoked Potentials

    Institute of Scientific and Technical Information of China (English)

    Caiping Hu; Lezheng Wu; De-Zheng Wu; Shixian Long

    2000-01-01

    Purposes: To compare the multi-channel pattern visual evoked potentials to Humphrey perimetry in the assessment of central visual function in primary open angle glaucoma.Methods: The multi-channel checkerboard reversal PVEPs waves to full-field and half-field stimulus of 25 normal persons and 74 patients with primary open angle glaucoma were recorded and analyzed, All patients were examined using Humphrey Field Analyzer. The area of visual field corresponding to the area of retina stimulated during multi-channel PVEPs testing were analysed, straight-line correlation and regression analyses of the various multi-channel PVEPs parameters and the total dB losses were performed.Results: The multi-channel PVEPs demonstrated a low detection rate compared with Humprey perimetry in the early glaucoma, absolute latency and field loss were correlated in the late stage of glaucoma, and absolute amplitude and field loss were not correlated.Conclusions: In relation to signalling “early” loss the multi-channel PVEPs was inferior to Humphrey perimetry, in late loss of primary open angle glaucoma, multi-channel PVEPs can provide a valuable, objective complement to Humphrey perimetry.

  10. Comparison of frequency distributions of doubled haploid and single seed descent lines in barley.

    Science.gov (United States)

    Choo, T M; Reinbergs, E; Park, S J

    1982-09-01

    Both doubled haploid (DH) and single seed descent (SSD) methods were used to derive homozygous lines from two crosses of barley. The frequency distributions of grain yield, heading date, and plant height of the DH and SSD lines were compared by the Mann-Whitney U test, Kolmogorov-Smirnov twosample test and Wald-Wolfowitz runs test. It was found that the DH lines distributed in the same manner as the SSD lines with respect to the three characters. The results indicated that although the SSD method had more opportunity for recombination than the DH method, it did not produce a sample of recombinants which differed significantly from the DH sample; thus both methods were equally efficient for use in deriving homozygous lines from F1 hybrids in a relatively short time.

  11. Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser

    Science.gov (United States)

    Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira

    A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.

  12. Frequency-doubled diode laser for direct pumping of Ti:sapphire lasers

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2012-01-01

    A single-pass frequency doubled high-power tapered diode laser emitting nearly 1.3 W of green light suitable for direct pumping of Ti:sapphire lasers generating ultrashort pulses is demonstrated. The pump efficiencies reached 75 % of the values achieved with a commercial solid-state pump laser....... However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the Ti:sapphire laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20...... fs are measured. These results open the opportunity of establishing diode laser pumped Ti:sapphire lasers for e.g. biophotonic applications like retinal optical coherence tomography or pumping of photonic crystal fibers for CARS microscopy....

  13. High-Power Blue Light Generation by External Frequency Doubling of an Optical Parametric Oscillator

    Institute of Scientific and Technical Information of China (English)

    毕勇; 张鸿博; 孙志培; 包照日格图; 李惠清; 孔宇鹏; 林学春; 王桂玲; 张杰; 侯玮; 李瑞宁; 崔大复; 许祖彦; 宋立维; 章萍; 崔建峰; 樊仲维

    2003-01-01

    We report on an all-solid-state high-power quasi-continuous blue light source by the frequency doubling of a signal wave from an optical parametric oscillator(OPO).A 50-mm-long LiB3O5(LBO)crystal is used for the OPO,which is pumped by a diode-pumped Nd:YAG green laser(10kHz,50ns).Tunable blue emission in a new nonlinear crystal BiB3O6(BiBO)is obtained with a wavelength range from 450 to 495 nm.The average power of the signal output is as high as 9.3 W from 924 to 970nm.The maximum output of the blue laser with the second harmonic walk-off compensation is 1.3 W average power at 470nm for 6.2 W of OPO signal light at 940nm.

  14. Compact intra-cavity frequency doubled line beam green laser by a laser diode array pumped

    Science.gov (United States)

    Yan, Boxia; Qi, Yan; Wang, Yanwei

    2016-10-01

    Compact, high power, and low-cost green laser light sources are needed in projection-related applications such as digital cinema, rear-projection television, simulators, and command and control stations. We report a LD array directly pumped intracavity SHG Nd:YVO4/PPMgLN laser without lens or waveguide in this letter. A compact 3.12 W green laser was demonstrated by intra-cavity frequency doubled using a PPMgLN bulk crystal by a 19-emitter LD array pumped(single bar), the conversion efficiency from input LD array was 9.2%. A line-beam output suitable for laser projectors was generated, which has the potential to be scalable to small volumes and low costs for laser projection displays.

  15. Laser cooling of beryllium ions using a frequency-doubled 626 nm diode laser.

    Science.gov (United States)

    Cozijn, F M J; Biesheuvel, J; Flores, A S; Ubachs, W; Blume, G; Wicht, A; Paschke, K; Erbert, G; Koelemeij, J C J

    2013-07-01

    We demonstrate laser cooling of trapped beryllium ions at 313 nm using a frequency-doubled extended cavity diode laser operated at 626 nm, obtained by cooling a ridge waveguide diode laser chip to -31°C. Up to 32 mW of narrowband 626 nm laser radiation is obtained. After passage through an optical isolator and beam shaping optics, 14 mW of 626 nm power remains of which 70% is coupled into an external enhancement cavity containing a nonlinear crystal for second-harmonic generation. We produce up to 35 μW of 313 nm radiation, which is subsequently used to laser cool and detect 6×10(2) beryllium ions, stored in a linear Paul trap, to a temperature of about 10 mK, as evidenced by the formation of Coulomb crystals. Our setup offers a simple and affordable alternative for Doppler cooling, optical pumping, and detection to presently used laser systems.

  16. Cold Testing Of A Radial Extraction Output Cavity For A Frequency-doubling Gyroklystron

    CERN Document Server

    Bharathan, K

    2004-01-01

    Research in the University of Maryland Gyroklystron program has centered around the development of a 17.136 GHz gyroklystron, that combines the gyrotron mechanism with the ballistic bunching of klystrons to produce a high power, high gain amplifier. The current tube is a 4- cavity (input, buncher, penultimate and output) coaxial, frequency doubling system that will be used as a driver for the Haimson Research Corporation (HRC) accelerator structure. This thesis presents the design, simulation, optimization, cold test methodology and performance data of a proposed radial extraction output cavity in which the microwave energy is extracted through an inner coaxial conductor in the TE01 circular mode. The positioning of dielectrics in the drift spaces and the effect of axial and radial misalignments between the inner and outer walls of the cavity were studied at depth and quantified. One advantage of this topology is that it reduces the size and complexity of the output waveguide chain otherwise needed to convert...

  17. [Retinal photocoagulation with a pulsed, frequency-doubled Nd:YAG laser (532 nm)].

    Science.gov (United States)

    Roider, J; Schiller, M; el Hifnawi, E S; Birngruber, R

    1994-12-01

    The small difference in wavelength between an argon laser (514 nm) and a frequency-doubled Nd:YAG laser (532 nm), together with the advantage of the solid-state technology, makes the Nd:YAG laser likely to play a major role in retinal photocoagulation in the near future. For technical reasons all frequency-doubled Nd:YAG lasers work in a quasi-continuous mode, emitting a burst of highly repetitive short laser pulses during the exposure time desired. We investigated the side effects due to high peak irradiances of those short laser pulse trains (Crystal Focus Nd:YAG laser, Emerald; pulse duration 1-10 microseconds, repetition rate 13 KHz) in rabbits in comparison with a standard argon laser system (Zeiss, Visulas, Argon II). The energy necessary for blanching the retina was similar in both cases. As opposed to the argon laser system, subretinal bubbles were regularly visible ophthalmoscopically with the Nd:YAG system, when average powers as high as 200 mW were used. The ED50 power for bubble formation is about 2-3 times above the ED50 power for blanching. Thermal calculations show that this bubble formation effect is likely to be related to the peak power of the short pulses. The hemorrhage threshold is similar in both systems. However, light microscopically there is no difference between the two laser systems. Panretinal photocoagulation (300-500 microns, 100-200 ms) in patients with proliferative diabetic retinopathy produced such bubbles about once per 1000 lesions.

  18. Influence of aspheric intraocular lens on frequency doubling technology and contrast sensitivity: a fellow eye study

    Directory of Open Access Journals (Sweden)

    Rodrigo França de Espíndola

    2014-12-01

    Full Text Available Purpose: To evaluate whether implantation of an aspheric intraocular lens (IOL results in reduced ocular aberrations and improved contrast sensitivity after cataract surgery and, therefore, changes on frequency-doubling technology (FDT testing. Methods: The present prospective clinical study enrolled 25 patients with bilateral cataract (50 eyes, who randomly received either an aspheric (Akreos AO or a spherical (Akreos Fit IOL in one eye and the other IOL in the second eye. Assessment 12 months postoperatively included photopic and mesopic contrast sensitivity testing. Higher-order aberrations (HOAs were computed. FDT testing was divided into four areas to evaluate the variation of the values at different points. The median values of the local pattern thresholds (median area contrast sensitivity [MACS] obtained with that division were calculated. Results: The Akreos AO group obtained statistically significantly lower values of HOAs and spherical aberration compared with the Akreos Fit group. There was a statistically significant between-group difference in contrast sensitivity under mesopic conditions at all spatial frequencies. No statistically significant differences were observed in mean deviation and pattern standard deviation. The aspheric IOL exhibited higher MACS in all areas, although a statistically significant difference was reached only in the 20-degree field area (P=0.043. Conclusion: Aspheric IOLs significantly reduced spherical aberration and HOAs, improving mesopic contrast sensitivity. Although there was a trend toward slightly improved FDT in the aspheric IOL group, it was not statistically significant.

  19. Double frequency piezoelectric transducer design for harmonic imaging purposes in NDT.

    Science.gov (United States)

    Montero de Espinosa, Francisco; Martínez, Oscar; Elvira Segura, Luis; Gómez-Ullate, Luis

    2005-06-01

    Harmonic imaging (HI) has emerged as a very promising tool for medical imaging, although there has been little published work using this technique in ultrasonic nondestructive testing (NDT). The core of the technique, which uses nonlinear propagation effects arising in the medium due to the microstructure or the existence of defects, is the ability to design transducers capable of emitting at one frequency and receiving at twice this frequency. The transducers that have been used so far are usually double crystal configurations with coaxial geometry, and commonly using a disc surrounded by a ring. Such a geometry permits the design of broadband transducers if each transducer element is adapted to the medium with its corresponding matching layers. Nevertheless, the different geometry of the emission and reception apertures creates difficulties when resolving the images. In this work, a new transducer design with different emission and reception apertures is resented. It makes use of the traditional construction procedures used to make piezocomposite transducers and the well-known theory of the mode coupling in piezoelectric resonators when the lateral dimensions are comparable with the thickness of the piezoceramic. In this work the design, construction, and characterization of a prototype to be used in NDT of metallic materials is presented. The acoustic field is calculated using water as a propagation medium, and these theoretical predictions then are compared with the experimental measurements. The predicted acoustic performances for the case of propagation in stainless steel are shown.

  20. Population and Coherence Transfer Induced by Double Frequency Sweeps in Half-Integer Quadrupolar Spin Systems

    Science.gov (United States)

    Iuga, Dinu; Schäfer, Hartmut; Verhagen, Rieko; Kentgens, Arno P. M.

    2000-12-01

    We have recently shown that the sensitivity of single- and multiple-quantum NMR experiments of half-integer (N/2) quadrupolar nuclei can be increased significantly by introducing so-called double frequency sweeps (DFS) in various pulse schemes. These sweeps consist of two sidebands generated by an amplitude modulation of the RF carrier. Using a time-dependent amplitude modulation the sidebands can be swept through a certain frequency range. Inspired by the work of Vega and Naor (J. Chem. Phys. 75, 75 (1981)), this is used to manipulate ±(m - 1) ↔ ±m (3/2 ≤ m ≤ N/2) satellite transitions in half-integer spin systems simultaneously. For 23Na (I = 3/2) and 27Al (I = 5/2) spins in single crystals it proved possible to transfer the populations of the outer ±m spin levels to the inner ±1/2 spin levels. A detailed analysis shows that the efficiency of this process is a function of the adiabaticity with which the various spin transitions are passed during the sweep. In powders these sweep parameters have to be optimized to satisfy the appropriate conditions for a maximum of spins in the powder distribution. The effects of sweep rate, sweep range, and RF field strength are investigated both numerically and experimentally. Using a DFS as a preparation period leads to significantly enhanced central transition powder spectra under both static and MAS conditions, compared to single pulse excitation. DFSs prove to be very efficient tools not only for population transfer, but also for coherence transfer. This can be exploited for the multiple- to single-quantum transfer in MQMAS experiments. It is demonstrated, theoretically and experimentally, that DFSs are capable of transferring both quintuple-quantum and triple-quantum coherence into single-quantum coherence in I = 5/2 spin systems. This leads to a significant enhancement in signal-to-noise ratio and strongly reduces the RF power requirement compared to pulsed MQMAS experiments, thus extending their applicability

  1. Efficient intracavity frequency doubling of a high-repetition-rate diode-pumped Nd:YAG laser.

    Science.gov (United States)

    Hanson, F; Poirier, P

    1994-10-01

    Efficient operation of a pulsed, high-repetition-rate diode-pumped and intracavity frequency-doubled Nd:YAG laser is reported. A 3-mm-diameter laser rod was side-pumped with a 5-bar stack of high-duty-cycle 1-cm diodearrays. The average Q-switched power at 1.06microum was 3.8 W at 1.33 kH(z), and more than 4 W at 0.532 ,microm wasobtained through intracavity frequency doubling with LiB(3)O(5).

  2. A 1.5-W frequency doubled semiconductor disk laser tunable over 40 nm at around 745 nm

    Science.gov (United States)

    Saarinen, Esa J.; Lyytikäinen, Jari; Ranta, Sanna; Rantamäki, Antti; Saarela, Antti; Sirbu, Alexei; Iakovlev, Vladimir; Kapon, Eli; Okhotnikov, Oleg G.

    2016-03-01

    We report on a semiconductor disk laser emitting 1.5 W of output power at the wavelength of 745 nm via intracavity frequency doubling. The high power level and the pumped with commercial low-cost 980 nm laser diode modules. Laser emission at 1490 nm was frequency-doubled with a bismuth borate crystal that was cut for type I critical phase matching. At the maximum output power, we achieved an optical-to-optical efficiency of 8.3% with beam quality parameter M2 below 1.5. The laser wavelength could be tuned with an intracavity birefringent plate from 720 to 764 nm.

  3. Double-grid finite-difference frequency-domain (DG-FDFD) method for scattering from chiral objects

    CERN Document Server

    Alkan, Erdogan; Elsherbeni, Atef

    2013-01-01

    This book presents the application of the overlapping grids approach to solve chiral material problems using the FDFD method. Due to the two grids being used in the technique, we will name this method as Double-Grid Finite Difference Frequency-Domain (DG-FDFD) method. As a result of this new approach the electric and magnetic field components are defined at every node in the computation space. Thus, there is no need to perform averaging during the calculations as in the aforementioned FDFD technique [16]. We formulate general 3D frequency-domain numerical methods based on double-grid

  4. Four-Wave Mixing of a Laser and Its Frequency-Doubled Version in a Multimode Optical Fiber

    Directory of Open Access Journals (Sweden)

    Hamed Pourbeyram

    2015-08-01

    Full Text Available It is shown that it is possible to couple a laser beam and its frequency-doubled daughter into a multimode optical fiber through the four-wave mixing nonlinear process and generate a new wavelength. The frequency-doubled daughter can be generated in an external crystal with a large second order nonlinearity. It is argued that while this possibility is within the design parameter range of conventional multimode optical fibers, it necessitates a lower-bound for the core-cladding refractive index contrast of the multimode optical fiber.

  5. Quartz optical filter for wavelength selection of frequency-doubled laser based on optical rotatory dispersion effect

    Institute of Scientific and Technical Information of China (English)

    Shan Zhang; Fuquan Wu; Wendi Wu; Haifeng Wang

    2007-01-01

    Based on the optical rotatory dispersion effect, an optical filter for selecting the second harmonic of a frequency-doubled laser is constructed from quartz in combination with polarizers. The operating principle is analyzed by matrix formulation, and the result indicates that the second harmonic of a frequency-doubled laser will be obtained when the rotation angle has a difference of (2n + 1)π/2 (n = 0, 1, 2, 3,… ) between the two polarizations of the second-harmonic laser and the fundamental laser. The spectrum of the output laser is taken by the AQ-6315A spectrometer, and the experimental results are in good agreement with the theoretical results.

  6. LDPC based time-frequency double differential space-time coding for multi-antenna OFDM systems

    Institute of Scientific and Technical Information of China (English)

    TIAN Ji-feng; JIANG Hai-ning; SONG Wen-tao; LUO Han-wen

    2006-01-01

    Differential space-time coding was proposed recently in the literature for multi-antenna systems, where neither the transmitter nor the receiver knows the fading coefficients. Among existing schemes, double differential space-time (DDST) coding is of special interest because it is applicable to continuous fast time-varying channels. However, it is less effective in frequency-selective fading channels. This paper's authors derived a novel time-frequency double differential space-time (TF-DDST)coding scheme for multi-antenna orthogonal frequency division multiplexing (OFDM) systems ina time-varying frequency-selective fading environment, where double differential space-time coding is introduced into both time domain and frequency domain. Our proposed TF-DDST-OFDM system has a low-complexity non-coherent decoding scheme and is robust for time- and frequency-selective Rayleigh fading. In this paper, we also propose the use of state-of-the-art low-density parity-check (LDPC) code in serial concatenation with our TF-DDST scheme as a channel code. Simulations revealed that the LDPC based TF-DDST OFDM system has low decoding complexity and relatively better performance.

  7. Specific features of low-frequency vibrational dynamics and low-temperature heat capacity of double-walled carbon nanotubes

    Science.gov (United States)

    Avramenko, M. V.; Roshal, S. B.

    2016-05-01

    A continuous model has been constructed for low-frequency dynamics of a double-walled carbon nanotube. The formation of the low-frequency part of the phonon spectrum of a double-walled nanotube from phonon spectra of its constituent single-walled nanotubes has been considered in the framework of the proposed approach. The influence of the environment on the phonon spectrum of a single double-walled carbon nanotube has been analyzed. A combined method has been proposed for estimating the coefficients of the van der Waals interaction between the walls of the nanotube from the spectroscopic data and the known values of the elastic moduli of graphite. The low-temperature specific heat has been calculated for doublewalled carbon nanotubes, which in the field of applicability of the model ( T nanotubes forming it.

  8. Laser at 532 nm by intracavity frequency-doubling in BBO

    Science.gov (United States)

    Yuan, Xiandan; Wang, Jinsong; Chen, Yongqi; Wu, Yulong; Qi, Yunfei; Sun, Meijiao; Wang, Qi

    2017-06-01

    A simple and compact linear resonator green laser at 532 nm is generated by intracavity frequency-doubling of a diode-side-pumped acousto-optically (AO) Q-switched Nd:YAG laser at 1064 nm. Two acousto-optic Q-switches were placed orthogonally with each other to improve the hold-off capacity. As high as 214 W of continuous-wave (CW) and 154 W of quasi-continuous-wave (QCW) output power at 1064 nm were obtained when the pumping power was 1598 W. The type I phase-matched BBO crystal was used as the nonlinear medium in the second harmonic generation. A green laser with an average output power of 37 W was obtained at a repetition rate of 20 kHz and a pulse width of 54 ns, which corresponds to pulse energy of 1.85 mJ per pulse and a peak power 34.26 kW, respectively. Project supported by the Beijing Engineering Technology Research Center of All-Solid-State Lasers Advanced Manufacturing, the National High Technology Research and Development Program of China (No. 2014AA032607), and the National Natural Science Foundation of China (Nos. 61404135, 61405186, 61308032, 61308033).

  9. A new solid-state, frequency-doubled neodymium-YAG photocoagulation system.

    Science.gov (United States)

    Jalkh, A E; Pflibsen, K; Pomerantzeff, O; Trempe, C L; Schepens, C L

    1988-06-01

    We have developed a solid-state laser system that produces a continuous green monochromatic laser beam of 532 nm by doubling the frequency of a neodymium-YAG laser wavelength of 1064 nm with a potassium-titamyl-phosphate crystal. Photocoagulation burns of equal size and intensity were placed in two rabbit eyes with the solid-state laser system and the regular green argon laser system, respectively, using the same slit-lamp mode of delivery. Histologic findings of lesion sections revealed no important differences between the two systems. In theory, the longer wavelength of the solid-state laser offers the advantages of less scattering in ocular media, higher absorption by oxyhemoglobin, and less absorption by macular xanthophyll than the 514-nm wavelength of the regular green argon laser. The solid-state laser has impressive technical advantages: it contains no argon-ion gas tube that wears out and is expensive to replace; it is much more power efficient, and thus considerably smaller and compact; it is sturdier and easily movable; it does not require external cooling; it uses a 220-V monophasic alternating current; and it requires little maintenance.

  10. Theory of intracavity-frequency-doubled solid-state four-level lasers

    Institute of Scientific and Technical Information of China (English)

    张行愚; 王青圃; 赵圣之; 李剑峰; 李平; 任承; 郑加安

    2002-01-01

    The spatial distributions of the pumping,the population inversion density,and the intracavity photon densities of the fundamental and the second harmonic are taken into account in the rate equations of the intracavity-frequency-doubled cw lasers.By normalizing the related parameters,it is shown that the general solution of these space-dependent rate equations is dependent upon three dimensionless parameters:the pump to laser-mode size ratio,the normalized pump level,and a parameter written as ηSHG,which is related to the ability of the nonlinear crystal to convert the fundamental to the second harmonic.By numerically solving these rate equations,a group of general curves are obtained to express the relations between the solution and the three dimensionless parameters.In addition,the optimal pump to laser-mode size ratio and the optimal ηSHG are determined.A comparison with the result obtained under the plane-wave approximation is also given.``

  11. Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal

    Science.gov (United States)

    Kurzke, Henning; Kiethe, Jan; Heuer, Axel; Jechow, Andreas

    2017-05-01

    The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, {{g}(2)}(0)=1.9+/- 0.1 , indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments.

  12. PATTERN ELECTRORETINOGRAPHY IN RELATION TO KINETIC AND STATIC PERIMETRY AND VISUAL ACUITY IN RETINITIS PIGMENTOSA

    Directory of Open Access Journals (Sweden)

    Petra Popović

    2002-12-01

    Full Text Available Background. This study was conducted to assess whether pattern ERG is a sensitive test in evaluating the retinal function in patients with retinitis pigmentosa. We wanted to determine how pattern ERG, reflecting the activity of inner retinal layers, is related to other psychophysical tests such as perimetry and visual acuity.Methods. An analysis was performed on 50 eyes of 25 patients with typical rod-cone retinitis pigmentosa. The standard Snellen visual acuity was tested. Visual field sensitivity was measured with automated static perimetry (Octopus G2 program where mean defect was taken as an index of visual field loss. In kinetic perimetry (Goldmann the average radius of the visual field measured with target II/4 and V/4 was calculated. Transient pattern ERG and all five flash ERG responses were also measured according to ISCEV standards. Amplitudes of pattern ERG P50 and N95 waves were compared to results of visual acuity and visual field testing.Results. In our group of 25 RP patients with visual acuity ranging from 0.16 to 1.0, PERG responses were preserved much better than full field ERGs. 72% of them had still recordable PERG responses, while 48% had cone and only 32% maximal responses. Scotopic rod responses were extinguished in all eyes. The normalized amplitudes of the PERG responses were also much higher (43.5% than cone (22.5% or maximal responses (4.5%. A strong correlation of both P50 and N95 amplitudes with Octopus mean defect index was found. In kinetic perimetry the correlation with PERG amplitudes was also high, but it was better with II/4 than with V/4 target. Patients with high preserved ERG responses had good visual acuity. In all patients with visual acuity less than 0.4 both flash and pattern ERG responses were already absent.Conclusions. This study shows that pattern ERG is an objective and sensitive test in evaluating the functional visual loss in retinitis pigmentosa. Amplitudes of P50 and N95 responses are linearly

  13. High power red laser at 671nm by intracavity frequency doubling of a Nd:YVO4 laser

    Institute of Scientific and Technical Information of China (English)

    Yao Ai-Yun; Hou Wei; Li Hui-Qing; Bi Yong; Li Rui-Ning; Geng Ai-Cong; Kong Yu-Peng; Cui Da-Fu; Xu Zu-Yan

    2005-01-01

    This paper reports a high-power quasi-continuous wave (quasi-CW) source of red laser at 671nm obtained by intracavity frequency doubling of a double-end-pumped 1342nm Nd:YVO4 laser, based on the nonlinear crystal LiB3O5 (LBO)The average output power of 2.9W at 671nm was obtained at the incident pump power of 19.5W. The overall optical to optical efficiency is 14.9%. We have analyzed the influence of the optimal pump size, the optimal focal position and the reduction of the thermal effect on high output. The combination of double-end-pumping and the quasi-CW performance greatly reduces the thermal effect.

  14. Angular Multiplexing Storage in Azo-polymer Liquid Crystal Films Using Shearing Interferometer of Double-frequency Grating

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jiangying; MING Hai; WANG Pei; WU Yunxia; XIE Jianping; ZHANG Qijin; LIU Jian

    2002-01-01

    In this paper, the shearing interferometer of a double-frequency grating (DFG) and a small compact Nd∶YVO4 double frequency laser at 532 nm are used to study the multiple storage in azo-polymer liquid crystal (PLC) films. In a principle experiment, the angle-encoded multiple gratings are recorded and the experimental results give triplex gratings at the same region in azo-PLC films, the angle between two adjacent grating vectors being 45°. Compared to the two-beam interferometer and four-wave mixing method, this method has simple configuration, high fringe contrast and quake-proof. A compatible angular multiplexing storage system in azo-PLC films is proposed.

  15. MgO:PPLN frequency doubling optical chips for green light generation: from lab research to mass production

    Science.gov (United States)

    Xu, Chang-Qing; Gan, Yi; Sun, Jian

    2012-03-01

    Laser displays require red, green and blue (RGB) laser sources each with a low-cost, a high wall-plug efficiency, and a small size. However, semiconductor chips that directly emit green light with sufficient power and efficiency are not currently available on the market. A practical solution to the "green" bottleneck is to employ diode pumped solid state laser (DPSSL) technology, in which a frequency doubling crystal is used. In this paper, recent progress of MgO doped periodically poled lithium niobate (MgO:PPLN) frequency doubling optical chips will be presented. It is shown that MgO:PPLN can satisfy all of the requirements for laser displays and is ready for mass production.

  16. Realization of 1.5 W 780 nm single-frequency laser by using cavity-enhanced frequency doubling of an EDFA boosted 1560 nm diode laser

    Science.gov (United States)

    Ge, Yulong; Guo, Shanlong; Han, Yashuai; Wang, Junmin

    2015-01-01

    We demonstrated a continuous-wave (CW) 780 nm laser with Watt-level output power by using external-cavity-enhanced frequency doubling of an Erbium-doped fiber amplifier (EDFA) boosted 1560 nm diode laser in a periodically-poled magnesium-oxide-doped lithium niobate (PPMgO:LN) bulk crystal. A 780 nm laser with maximum output power of 1.5 W is obtained at an incident 1560 nm laser of 2.05 W, corresponding to a doubling efficiency of 73%. The typical fluctuation of 780 nm laser's power is 1.2% (rms) in about 30 min. This 780 nm laser can be potentially applied to laser cooling and manipulation of rubidium atoms, generating 1560 nm squeezed vacuum field as well as 1560 nm continuous-variable entanglement based on optical parametric oscillator if additional locking and noise suppression is applied.

  17. 双程腔内倍频激光器的谐波晶体腔内位置的理论研究%The Theory Research on the Location of a Frequency Doubling Crystal in a Double-pass Intracavity Frequency Doubling Laser

    Institute of Scientific and Technical Information of China (English)

    程一斌

    2000-01-01

    In this paper, the location of a frequency doubling crystal in a double-pass intra cavity frequency doubling and plano- concave confignration' s laser whose output was inone direc tion was analyzed in theory, and the formula of the suitable space between the frequency doubling crystal and the fiat mirror was obtained.%从理论上分析了平-凹腔结构的双程谐波、单方向输出的腔内谐波激光器的谐 波晶体腔内位置的选择,获得了谐波晶体与全反射镜的合理间距的解析式。

  18. MOSFET technologies for double-pole four-throw radio-frequency switch

    CERN Document Server

    Srivastava, Viranjay M

    2014-01-01

    This book provides analysis and discusses the design of various MOSFET technologies which are used for the design of Double-Pole Four-Throw (DP4T) RF switches for next generation communication systems. The authors discuss the design of the (DP4T) RF switch by using the Double-Gate (DG) MOSFET, as well as the Cylindrical Surrounding double-gate (CSDG) MOSFET.  The effect of HFO2 (high dielectric material) in the design of DG MOSFET and CSDG MOSFET  is also explored. Coverage includes comparison of Single-gate MOSFET and Double-gate MOSFET switching parameters, as well as testing of MOSFETs parameters using image acquisition.  ·         Provides a single-source reference to the latest technologies for the design of Double-gate MOSFET, Cylindrical Surrounding double-gate MOSFET and HFO2 based MOSFET; ·         Explains the design of RF switches using the technologies presented and simulates switches; ·         Verifies parameters and discusses feasibility of devices and switches.

  19. Wavelets, period-doubling, and time-frequency localization with application to organization of convection over the tropical western Pacific

    Science.gov (United States)

    Weng, Hengyi; Lau, K.-M.

    1994-01-01

    In this paper, preliminary results in using orthogonal and continuous wavelet transform (WT) to identify period doubling and time-frequency localization in both synthetic and real data are presented. First, the Haar WT is applied to synthetic time series derived from a simple nonlinear dynamical system- a first-order quadratic difference equation. Second, the complex Morlet WT is used to study the time-frequency localization of tropical convection based on a high-resolution Japanese Geostationary Meteorological Satellite infrared (IR) radiance dataset. The Haar WT of the synthetic time series indicates the presence and distinct separation of multiple frequencies in a period-doubling sequence. The period-doubling process generates a multiplicity of intermediate frequencies, which are manifested in the nonuniformity in time with respect to the phase of oscillations in the lower frequencies. Wavelet transform also enables the detection of extremely weak signals in high-order subharmonics resulting from the period-doubling bifurcations. These signals are either undetected or considered statistically insignificant by traditional Fourier analysis. The Morlet WT of the IR radiance dataset indicates the presence of multiple timescales, which are localized in both frequency and time. There are two regimes in the variation of IR radiance, corresponding to the wet and dry periods. Multiple timescales, ranging from semidiurnal, diurnal, synoptic, to intraseasonal with embedding structures, are active in the wet regime. In particular, synoptic variability is more prominent during the wet phase of an intensive intraseasonal cycle. These are not only consistent with, but also show more details than, previous findings by using other techniques. The phase-locking relationships among the oscillations with different time-scales suggest that both synoptic and intraseasonal variations may be mixed oscillations due to the interaction of self-excited oscillations in the tropical

  20. Clinical application of objective perimetry using multifocal visual evoked potentials in glaucoma practice.

    Science.gov (United States)

    Graham, Stuart L; Klistorner, Alexander I; Goldberg, Ivan

    2005-06-01

    To evaluate the role of objective perimetry using multifocal visual evoked potentials (mVEPs) in glaucoma practice, and to assess its utility in patients with inconclusive standard automated perimetry findings. Method A retrospective case series of 436 consecutive subjects referred for glaucoma investigation who underwent testing with the AccuMap V1.3 mVEP system (ObjectiVision Pty, Ltd, Sydney, New South Wales, Australia) within a defined 12-month period. Sensitivity was determined by comparing this testing with that of standard automated perimetry and that used in a subgroup in whom masked stereoscopic optic disc photographs were used as an alternative reference standard. Overall clinical diagnostic outcomes were assessed. The mVEP changes were correlated with the stage of disease and Humphrey mean deviation (r = 0.78). The overall sensitivity for detecting glaucoma with established subjective field loss was 97.5% (early glaucoma, 95.0%), whereas 92.2% of low-risk suspects had normal mVEPs. When masked disc assessment alone was used for diagnosis of abnormality, sensitivity of mVEP (80.6%) and Humphrey visual field results (81.9%) were similar, but mVEP specificity was better (89.2% vs 79.5%). The mVEP was particularly useful in assessing excessive subjective field loss (45 eyes) by showing a much closer correlation with the clinical picture. Multifocal VEP is an effective method for detecting visual field loss in glaucoma. It provides a valuable aid to the clinician in categorizing patients with unreliable, variable, unconfirmed, or excessive subjective field loss.

  1. Low frequency solitons and double layers in a magnetized plasma with two temperature electrons

    Energy Technology Data Exchange (ETDEWEB)

    Rufai, O. R. [Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535 (South Africa); Bharuthram, R. [Office of the Deputy Vice Chancellor (Academic), University of the Western Cape, Bellville (South Africa); Singh, S. V. [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai-410218 (India); School of Chemistry and Physics, University of Kwa-Zulu Natal, Durban (South Africa); Lakhina, G. S. [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai-410218 (India)

    2012-12-15

    Finite amplitude non-linear ion-acoustic solitary waves and double layers are studied in a magnetized plasma with cold ions fluid and two distinct groups of Boltzmann electrons, using the Sagdeev pseudo-potential technique. The conditions under which the solitary waves and double layers can exist are found both analytically and numerically. We have shown the existence of negative potential solitary waves and double layers for subsonic Mach numbers, whereas in the unmagnetized plasma they can only in the supersonic Mach number regime. For the plasma parameters in the auroral region, the electric field amplitude of the solitary structures comes out to be 49 mV/m which is in agreement of the Viking observations in this region.

  2. Comparison and characterization of efficient frequency doubling at 397.5 nm with PPKTP, LBO and BiBO crystals

    CERN Document Server

    Wen, Xin; Wang, Junmin

    2016-01-01

    A continuous-wave Ti:sapphire laser at 795 nm is frequency doubled in a bow-tie type enhancement four-mirror ring cavity with LiB3O5 (LBO), BiB3O6 (BiBO), and periodically polled KTiOPO4 (PPKTP) crystals, respectively. The properties of 397.5 nm ultra-violet (UV) output power, beam quality, stability for these different nonlinear crystals are investigated and compared. For PPKTP crystal, the highest doubling efficiency of 58.1% is achieved from 191 mW of 795 nm mode-matched fundamental power to 111 mW of 397.5 nm UV output. For LBO crystal, with 1.34 W of mode-matched 795 nm power, 770 mW of 397.5 nm UV output is achieved, implying a doubling efficiency of 57.4%. For BiBO crystal, with 323 mW of mode-matched 795 nm power, 116 mW of 397.5 nm UV output is achieved, leading to a doubling efficiency of 35.9%. The generated UV radiation has potential applications in the fields of quantum physics

  3. 750 nm 1.5 W frequency-doubled semiconductor disk laser with a 44 nm tuning range.

    Science.gov (United States)

    Saarinen, Esa J; Lyytikäinen, Jari; Ranta, Sanna; Rantamäki, Antti; Sirbu, Alexei; Iakovlev, Vladimir; Kapon, Eli; Okhotnikov, Oleg G

    2015-10-01

    We demonstrate 1.5 W of output power at the wavelength of 750 nm by intracavity frequency doubling a wafer-fused semiconductor disk laser diode-pumped at 980 nm. An optical-to-optical efficiency of 8.3% was achieved using a bismuth borate crystal. The wavelength of the doubled emission could be tuned from 720 to 764 nm with an intracavity birefringent plate. The beam quality parameter M2 of the laser output was measured to be below 1.5 at all pump powers. The laser is a promising tool for biomedical applications that can take advantage of the large penetration depth of light in tissue in the 700-800 nm spectral range.

  4. Ultra-flat and broad optical frequency combs generation based on novel dispersion-flattened double-slot microring resonator

    Science.gov (United States)

    Wang, Yuanwu; Zhang, Minming; Lu, Luluzi; Li, Meifeng; Wang, Jinghao; Zhou, Feiya; Dai, Jing; Deng, Lei; Liu, Deming

    2016-01-01

    In this paper, a novel double-slot microring resonator is proposed to produce flat dispersion of 0-3.8 ps/(nm km) over 1150 nm wavelength range. Moreover, the dispersion tailoring with different structural parameters of the proposed microring resonator is analyzed and simulated. The simulation results show that the dispersion fluctuation can be tailored by the height of the central and bottom As2S3 layer, and the slope can be adjusted by the waveguide width and lower SiO2 slot thickness. Furthermore, by means of the Lugiato-Lefever equation, an ultra-flat and broad optical frequency comb with 7-dB bandwidth of 1155 nm (1855-3010 nm) is obtained based on such dispersion-optimized resonator. The proposed double-slot microring resonator shows potential application in both telecommunication and mid-infrared research domain.

  5. A Frequency-Domain Adaptive Filter (FDAF) Prediction Error Method (PEM) Framework for Double-Talk-Robust Acoustic Echo Cancellation

    DEFF Research Database (Denmark)

    Gil-Cacho, Jose M.; van Waterschoot, Toon; Moonen, Marc

    2014-01-01

    In this paper, we propose a new framework to tackle the double-talk (DT) problem in acoustic echo cancellation (AEC). It is based on a frequency-domain adaptive filter (FDAF) implementation of the so-called prediction error method adaptive filtering using row operations (PEM-AFROW) leading...... to the FDAF-PEM-AFROW algorithm. We show that FDAF-PEM-AFROW is by construction related to the best linear unbiased estimate (BLUE) of the echo path. We depart from this framework to show an improvement in performance with respect to other adaptive filters minimizing the BLUE criterion, namely the PEM...

  6. A Compact 532-nm Source by Frequency Doubling of a Diode Stack End-Pumped Nd:YAG Slab Laser

    Institute of Scientific and Technical Information of China (English)

    ZHANG Heng-Li; LIU Xiao-Meng; LI Dai-Jun; SHI Peng; Alex Schell; Claus Rüdige Haas; Du Ke-Ming

    2007-01-01

    A near-diffraction-limited green source is generated at 1 kHz repetition rate by frequency doubling ofa diode stack end-pumped electro-optically Q-switched Nd:YAG slab laser. We obtain 9.7mJ green light with pulse width of 12.2ns at a repetition rates of 1 kHz. The pump to green optical conversion efficiency is 12.9%. The energy pulse stability at 532nm is about 0.8%.

  7. Highly-Efficient Blue-Light Generation by Intracavity Frequency Doubling with LiB3O5

    Institute of Scientific and Technical Information of China (English)

    林学春; 李瑞宁; 崔大复; 姚爱云; 冯衍; 毕勇; 许祖彦

    2002-01-01

    We have investigated the generation of highly-efficient blue light in critically type-I phase-matched LiBsO5(LBO) with intracavity frequency doubling of diode-pumped Nd: YA G laser. A maximum output power of 502 m W at 473nm blue light was obtained and the overall optical-to-optical efficiency is up to 11.2%. To the best of our knowledge, this is the highest conversion efficiency for 473 nm output using a diode pumped Nd:YAG laser through LBO.

  8. LD-pumped Nd:YVO sub 4 frequency-doubled by CPM LBO laser at 671 nm

    CERN Document Server

    Zheng Quan; Qian Long Sheng; Zhao Ling

    2001-01-01

    A design of LD-pumped high efficient Nd:YVO sub 4 /LBO red laser is reported. Using critical phase-matching LBO for the first time, 671 nm red laser is obtained by 1.342 mu m intracavity frequency doubling. With 800 mW incident pump laser, 52 mW and 97 mW TEM00 mode red laser output are obtained by II-typed and I-typed LBO. The optical-to-optical conversions are up to 6.5% and 12.1% respectively

  9. Doubling of coastal flooding frequency within decades due to sea-level rise

    OpenAIRE

    Sean Vitousek; Patrick L. Barnard; Fletcher, Charles H.; Neil Frazer; Li Erikson; Curt D. Storlazzi

    2017-01-01

    Global climate change drives sea-level rise, increasing the frequency of coastal flooding. In most coastal regions, the amount of sea-level rise occurring over years to decades is significantly smaller than normal ocean-level fluctuations caused by tides, waves, and storm surge. However, even gradual sea-level rise can rapidly increase the frequency and severity of coastal flooding. So far, global-scale estimates of increased coastal flooding due to sea-level rise have not considered elevated...

  10. Relay Selection Based Double-Differential Transmission for Cooperative Networks with Multiple Carrier Frequency Offsets: Model, Analysis, and Optimization

    Science.gov (United States)

    Zhao, Kun; Zhang, Bangning; Pan, Kegang; Liu, Aijun; Guo, Daoxing

    2014-07-01

    Due to the distributed nature, cooperative networks are generally subject to multiple carrier frequency offsets (MCFOs), which make the channels time-varying and drastically degrade the system performance. In this paper, to address the MCFOs problem in detect-andforward (DetF) multi-relay cooperative networks, a robust relay selection (RS) based double-differential (DD) transmission scheme, termed RSDDT, is proposed, where the best relay is selected to forward the source's double-differentially modulated signals to the destination with the DetF protocol. The proposed RSDDT scheme can achieve excellent performance over fading channels in the presence of unknown MCFOs. Considering double-differential multiple phase-shift keying (DDMPSK) is applied, we first derive exact expressions for the outage probability and average bit error rate (BER) of the RSDDT scheme. Then, we look into the high signal-to-noise ratio (SNR) regime and present simple and informative asymptotic outage probability and average BER expressions, which reveal that the proposed scheme can achieve full diversity. Moreover, to further improve the BER performance of the RSDDT scheme, we investigate the optimum power allocation strategy among the source and the relay nodes, and simple analytical solutions are obtained. Numerical results are provided to corroborate the derived analytical expressions and it is demonstrated that the proposed optimum power allocation strategy offers substantial BER performance improvement over the equal power allocation strategy.

  11. Efficiency of non-linear frequency conversion of double-scale pico-femtosecond pulses of passively mode-locked fiber laser.

    Science.gov (United States)

    Smirnov, Sergey V; Kobtsev, Sergey M; Kukarin, Sergey V

    2014-01-13

    For the first time we report the results of both numerical simulation and experimental observation of second-harmonic generation as an example of non-linear frequency conversion of pulses generated by passively mode-locked fiber master oscillator in different regimes including conventional (stable) and double-scale (partially coherent and noise-like) ones. We show that non-linear frequency conversion efficiency of double-scale pulses is slightly higher than that of conventional picosecond laser pulses with the same energy and duration despite strong phase fluctuations of double-scale pulses.

  12. Design and analysis of a new high frequency double-servo direct drive rotary valve

    Science.gov (United States)

    Zhu, Muzhi; Zhao, Shengdun; Li, Jingxiang

    2016-12-01

    Researchers have investigated direct drive valve for many years to solve problems, such as fluid force imbalance and switching frequency. The structure of the rotary valve has received considerable research interest because of its favorable dynamic properties and simple structure. This paper studied the high frequency doubleservo direct drive rotary valve (DDRV), and proposed a novel structure and drive method satisfying high reversing frequency and adequate quantity of flow. Servo motors are integrated into the valve by the innovative structure, which is designed to equilibrate the unbalanced radial fluid force with the symmetric distributed oil ports. Aside from the fast reversing function of the valve, the DDRV presented high performance in linearity of the flow quantity and valve opening as a result of the fan-shaped flow ports. In addition, a computational fluid dynamics (CFD) method based on Fluent was conducted to verify the flux regulation effect of the height change of the adjustable boss.

  13. Investigation of optical inhomogeneity of MgO:PPLN crystals for frequency doubling of 1560 nm laser

    Science.gov (United States)

    Guo, Shanlong; Ge, Yulong; Han, Yashuai; He, Jun; Wang, Junmin

    2014-09-01

    The asymmetrical phase-matching temperature tuning curves of periodically-poled 5%-mol MgO-doped lithium niobate (MgO:PPLN) bulk crystals for frequency doubling of 1560 nm telecom laser have been observed experimentally and analyzed theoretically. We find that the asymmetrical phenomena are resulted from the variation in the extraordinary refractive index by the doping concentration inhomogeneity of the crystals. The critical parameters of phase-matching temperature mismatching γ(γ=δTpm/ΔT, in which δTpm is the change of the phase-matching temperature due to the doping concentration inhomogeneity, and ΔT is the temperature acceptance bandwidth) and the thermal refractive index ∂(Δn)/∂T are investigated. Our analysis method is not only a reasonable explanation to the experiment, but also can be a simple evaluation way of optical quality of the given MgO:PPLN bulk crystals. Moreover, the MgO:PPLN bulk crystal is used in single-pass configuration for frequency doubling a 4.4 W Erbium-doped fiber amplifier boosted 1560 nm telecom laser, and 300 mW of tunable 780 nm laser is obtained, corresponding to a conversion efficiency of 6.9%. This source provides a simple and compact laser system for rubidium atom cooling and manipulation experiments.

  14. Effects of different levels of intraocular stray light on kinetic perimetry findings.

    Directory of Open Access Journals (Sweden)

    Kazunori Hirasawa

    Full Text Available To evaluate the effect of different levels of intraocular stray light on kinetic perimetry findings.Twenty-five eyes of 25 healthy young participants were examined by automated kinetic perimetry (Octopus 900 using Goldmann stimuli III4e, I4e, I3e, I2e, and I1e. Each stimulus was presented with a velocity of 3°/s at 24 meridians with 15° intervals. Four levels of intraocular stray light were induced using non-white opacity filter (WOF filters and WOFs applied to the clear plastic eye covers of the participants. The visual acuity, pupil diameter, isopter area, and kinetic sensitivity of each meridian were analyzed for each WOF density.Visual acuity deteriorated with increasing WOF densities (p < 0.01. With a visual acuity of 0.1 LogMAR units, the isopter areas for III4e, I4e, I3e, I2e, and I1e decreased by -32.7 degree2 (-0.2%, -255.7 degree2 (-2.6%, -381.2 degree2 (-6.2%, -314.8 degree2 (-12.8%, and -59.2 degree2 (-15.2%, respectively; kinetic sensitivity for those stimuli decreased by -0.1 degree (-0.1%, -0.8 degree (-1.4%, -1.6 degree (-3.7%, -2.7 degree (-9.7%, and -1.7 degree (-16.2%, respectively. The pupil diameter with each WOF density was not significantly different.Kinetic perimetry measurements with a high-intensity stimulus (i.e., III4e were unaffected by intraocular stray light. In contrast, measurements with the I4e, I3e, I2e, and I1e stimuli, especially I2e and I1e, were affected. Changes in the shape of the isopter resulting from opacity must be monitored, especially in cases of smaller and lower-intensity stimuli.

  15. Frequency analysis of tick quotes on foreign currency markets and the double-threshold agent model

    Science.gov (United States)

    Sato, Aki-Hiro

    2006-09-01

    Power spectrum densities for the number of tick quotes per minute (market activity) on three currency markets (USD/JPY, EUR/USD, and JPY/EUR) are analyzed for periods from January 2000 to December 2000. We find some peaks on the power spectrum densities at a few minutes. We develop the double-threshold agent model and confirm that the corresponding periodicity can be observed for the activity of this model even though market participants perceive common weaker periodic information than threshold for decision-making of them. This model is numerically performed and theoretically investigated by utilizing the mean-field approximation. We propose a hypothesis that the periodicities found on the power spectrum densities can be observed due to nonlinearity and diversity of market participants.

  16. The Open Perimetry Interface: an enabling tool for clinical visual psychophysics.

    Science.gov (United States)

    Turpin, Andrew; Artes, Paul H; McKendrick, Allison M

    2012-01-01

    Perimeters are commercially available instruments for measuring various attributes of the visual field in a clinical setting. They have several advantages over traditional lab-based systems for conducting vision experiments, including built-in gaze tracking and calibration, polished appearance, and attributes to increase participant comfort. Prior to this work, there was no standard to control such instruments, making it difficult and time consuming to use them for novel psychophysical experiments. This paper introduces the Open Perimetry Interface (OPI), a standard set of functions that can be used to control perimeters. Currently the standard is partially implemented in the open-source programming language R on two commercially available instruments: the Octopus 900 (a projection-based bowl perimeter produced by Haag-Streit, Switzerland) and the Heidelberg Edge Perimeter (a CRT-based system produced by Heidelberg Engineering, Germany), allowing these instruments to be used as a platform for psychophysical experimentation.

  17. Double Space Time Transmit Diversity OFDM System with Antenna Shuffling in Spatial Correlated Frequency Selective MIMO Channels

    Science.gov (United States)

    Zhou, Liang; Shimizu, Masahiko

    In this paper, we study low complexity transceiver for double space time transmit diversity (DSTTD) and orthogonal frequency division multiplexing (OFDM) system with antenna shuffling. Firstly, we propose a novel antenna shuffling method based on the criterion of minimizing the condition number of channel correlation matrix. The condition number is an indicator about the quality of the channel. By selecting the minimum of condition number which has better channel quality, consequently, a linear detector with respect to this new channel may achieve better performance results. A low complexity variant of the condition number calculation is also proposed, and it is shown that this criterion can be reduced to the minimum mean square error (MMSE) based criterion. Furthermore, the weighted soft decision Viterbi decoding is applied to mitigate noise enhancement inherent to zero forcing (ZF) and MMSE linear receivers and improve error rate performance. Next, we propose an algorithm to reduce the amount of feedback by exploiting the fact that the channel frequency responses across OFDM subcarriers are correlated. In the proposed algorithm, subcarriers are clustered in blocks, which are allocated the same shuffling pattern with the largest number of the shuffling patterns in the cluster. This way, the signaling overhead can be reduced in comparison with each subcarrier based feedback. Extensive simulations show that the proposed techniques for DSTTD-OFDM system outperform other existing techniques under both uncorrelated and highly spatial correlated frequency selective MIMO fading channels.

  18. Double resonance experiments in low magnetic field: dynamic polarization of protons by (14)N and measurement of low NQR frequencies.

    Science.gov (United States)

    Seliger, J; Zagar, V

    2009-08-01

    The possibilities of dynamically polarizing proton spin system via the quadrupole (14)N spin system in low magnetic field are analyzed. The increase of the proton magnetization is calculated. The polarization rate of the proton spin system is related to the transition probabilities per unit time between the (14)N quadrupole energy levels and proton energy levels. The experiments performed in 1,3,5-triazine confirm the results of the theoretical analysis. A new double resonance technique is proposed for the measurement of nuclear quadrupole resonance frequencies nu(Q) of the order of 100kHz and lower. The technique is based on magnetic field cycling between a high and a low static magnetic field and observation of the proton NMR signal in the high magnetic field. In the low magnetic field the quadrupole nuclei and protons resonantly interact at the proton Larmor frequency nu(H)=nu(Q)/2. The quadrupole nuclei are simultaneously excited by a resonant rf magnetic field oriented along the direction of the low static magnetic field. The experimental procedure is described and the sensitivity of the new technique is estimated. Some examples of the measurement of low (14)N and (2)H nuclear quadrupole resonance frequencies are presented.

  19. Design of Frequency Selective Surface with Double Bands%双带频率选择表面设计

    Institute of Scientific and Technical Information of China (English)

    曲宝龙; 李旭东; 朱鹏刚

    2012-01-01

    In order to realize double-band properties of frequency selective surface (FSS), the composite element FSS, composed of rectangle grid and three-ring loop element, is presented. The spectral domain solution method is described in detail for FSS. The frequency response properties of FSS are analyzed for electromagnetic waves with different incident angles and polarizations based on the spectral domain method. The result shows that the designed FSS can maintain stable double-band, flat top transmission and sharp skirt properties for electromagnetic waves with different incidence angles and polarizations. The double-band properties show stop-band from 1. 8 GHz to 5.4 GHz and pass-band from 5.4 GHz to 20.0 GHz. The resonant frequency of stop-band is situated at about 3. 1 GHz, and the bandwidth of flat top transmission is over 14.3 GHz at —4 dB. The sharp skirt properties show that the S-band signal is reflected intensively and other band signals are transmitted, and multi-band communication is achieved. The composite FSS can be used in satellite communications, radomes and other fields.%为了实现频率选择表面(FSS)的双带特性,设计了由矩形栅格和三圆环组合单元FSS.对FSS的谱域求解方法进行了详细的描述.采用谱域法分析了不同角度和极化入射波下FSS的频率响应性能.结果表明,所设计的FSS对于不同入射角度和极化电磁波具有稳定的双带、平顶传输及陡峭下降边缘特性.双带特性大致表现为1.8~5.4 GHz的阻带和5.4~20.0 GHz的通带.阻带谐振频率稳定在3.1 GHz左右,而通带在-4 dB的平顶传输带宽达14.3 GHz以上.其陡峭下降边缘特性表现为S波段信号强烈反射,而其他波段信号通过,从而实现多波段通讯.该结构FSS可应用于卫星通信、雷达罩及其他相关领域.

  20. Visual discrimination training improves Humphrey perimetry in chronic cortically induced blindness.

    Science.gov (United States)

    Cavanaugh, Matthew R; Huxlin, Krystel R

    2017-05-09

    To assess if visual discrimination training improves performance on visual perimetry tests in chronic stroke patients with visual cortex involvement. 24-2 and 10-2 Humphrey visual fields were analyzed for 17 chronic cortically blind stroke patients prior to and following visual discrimination training, as well as in 5 untrained, cortically blind controls. Trained patients practiced direction discrimination, orientation discrimination, or both, at nonoverlapping, blind field locations. All pretraining and posttraining discrimination performance and Humphrey fields were collected with online eye tracking, ensuring gaze-contingent stimulus presentation. Trained patients recovered ∼108 degrees(2) of vision on average, while untrained patients spontaneously improved over an area of ∼16 degrees(2). Improvement was not affected by patient age, time since lesion, size of initial deficit, or training type, but was proportional to the amount of training performed. Untrained patients counterbalanced their improvements with worsening of sensitivity over ∼9 degrees(2) of their visual field. Worsening was minimal in trained patients. Finally, although discrimination performance improved at all trained locations, changes in Humphrey sensitivity occurred both within trained regions and beyond, extending over a larger area along the blind field border. In adults with chronic cortical visual impairment, the blind field border appears to have enhanced plastic potential, which can be recruited by gaze-controlled visual discrimination training to expand the visible field. Our findings underscore a critical need for future studies to measure the effects of vision restoration approaches on perimetry in larger cohorts of patients. Copyright © 2017 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.

  1. Arm-length stabilisation for interferometric gravitational-wave detectors using frequency-doubled auxiliary lasers.

    Science.gov (United States)

    Mullavey, Adam J; Slagmolen, Bram J J; Miller, John; Evans, Matthew; Fritschel, Peter; Sigg, Daniel; Waldman, Sam J; Shaddock, Daniel A; McClelland, David E

    2012-01-02

    Residual motion of the arm cavity mirrors is expected to prove one of the principal impediments to systematic lock acquisition in advanced gravitational-wave interferometers. We present a technique which overcomes this problem by employing auxiliary lasers at twice the fundamental measurement frequency to pre-stabilise the arm cavities' lengths. Applying this approach, we reduce the apparent length noise of a 1.3 m long, independently suspended Fabry-Perot cavity to 30 pm rms and successfully transfer longitudinal control of the system from the auxiliary laser to the measurement laser.

  2. Arm-length stabilisation for interferometric gravitational-wave detectors using frequency-doubled auxiliary lasers

    CERN Document Server

    Mullavey, Adam J; Miller, John; Evans, Matthew; Fritschel, Peter; Sigg, Daniel; Waldman, Sam J; Shaddock, Daniel A; McClelland, David E

    2011-01-01

    Residual motion of the arm cavity mirrors is expected to prove one of the principal impediments to systematic lock acquisition in advanced gravitational-wave interferometers. We present a technique which overcomes this problem by employing auxiliary lasers at twice the fundamental measurement frequency to pre-stabilise the arm cavities' lengths. Applying this approach, we reduce the apparent length noise of a 1.3 m long, independently suspended Fabry-Perot cavity to 30 pm rms and successfully transfer longitudinal control of the system from the auxiliary laser to the measurement laser.

  3. Highly efficient, widely tunable, 10-Hz parametric amplifier pumped by frequency-doubled femtosecond Ti:sapphire laser pulses.

    Science.gov (United States)

    Zhang, J Y; Xu, Z; Kong, Y; Yu, C; Wu, Y

    1998-05-20

    We report a 10-Hz, highly efficient, widely tunable (from the visible to the IR), broadband femtosecond optical parametric generator and optical parametric amplifier (OPA) in BBO, LBO, and CBO crystals pumped by the frequency-doubled output of a regeneratively amplified Ti:sapphire laser at 400 nm. The output of the system is continuously tunable from 440 nm to 2.5 microm with a maximum overall efficiency of approximately 25% at 670 nm and an optical conversion efficiency of more than 36% in the OPA stage. The effects of the seed beam energy, the type of the crystal and the crystal length, and the pumping energy of the output of the OPA, such as the optical efficiency, the bandwidth, the pulse duration, and the group velocity mismatch between the signal and the idler and between the seeder and the pump, are investigated. The results provide useful information for optimization of the design of the system.

  4. Intra-cavity frequency-doubled mode-locked semiconductor disk laser at 325 nm.

    Science.gov (United States)

    Bek, Roman; Baumgärtner, Stefan; Sauter, Fabian; Kahle, Hermann; Schwarzbäck, Thomas; Jetter, Michael; Michler, Peter

    2015-07-27

    We present a passively mode-locked semiconductor disk laser (SDL) emitting at 650nm with intra-cavity second harmonic generation to the ultraviolet (UV) spectral range. Both the gain and the absorber structure contain InP quantum dots (QDs) as active material. In a v-shaped cavity using the semiconductor samples as end mirrors, a beta barium borate (BBO) crystal is placed in front of the semiconductor saturable absorber mirror (SESAM) for pulsed UV laser emission in one of the two outcoupled beams. Autocorrelation (AC) measurements at the fundamental wavelength reveal a FWHM pulse duration of 1.22ps. With a repetition frequency of 836MHz, the average output power is 10mW per beam for the red emission and 0.5mW at 325nm.

  5. Injection-locking of two frequency-doubled lasers with 3.2 GHz offset for driving Raman transitions with low photon scattering in $^{43}$Ca$^+$

    CERN Document Server

    Linke, N M; Lucas, D M

    2013-01-01

    We describe the injection locking of two infrared (794 nm) laser diodes which are each part of a frequency doubled laser system. An acousto-optic modulator (AOM) in the injection path gives an offset of 1.6 GHz between the lasers for driving Raman transitions between states in the hyperfine split (by 3.2 GHz) ground level of $^{43}$Ca$^+$. The offset can be disabled for use in $^{40}$Ca$^+$. We measure the relative linewidth of the frequency-doubled beams to be 42 mHz in an optical heterodyne measurement. The use of both injection locking and frequency doubling combines spectral purity with high optical power. Our scheme is applicable for providing Raman beams across other ion species and neutral atoms where coherent optical manipulation is required.

  6. Double-gated Si NW FET sensors: Low-frequency noise and photoelectric properties

    Science.gov (United States)

    Gasparyan, F.; Khondkaryan, H.; Arakelyan, A.; Zadorozhnyi, I.; Pud, S.; Vitusevich, S.

    2016-08-01

    The transport, noise, and photosensitivity properties of an array of silicon nanowire (NW) p+-p-p+ field-effect transistors (FETs) are investigated. The peculiarities of photosensitivity and detectivity are analyzed over a wide spectrum range. The absorbance of p-Si NW shifts to the short wavelength region compared with bulk Si. The photocurrent and photosensitivity reach increased values in the UV range of the spectrum at 300 K. It is shown that sensitivity values can be tuned by the drain-source voltage and may reach record values of up to 2-4 A/W at a wavelength of 300 nm at room temperature. Low-frequency noise studies allow calculating the photodetectivity values, which increase with decreasing wavelength down to 300 nm. We show that the drain current of Si NW biochemical sensors substantially depends on pH value and the signal-to-noise ratio reaches the high value of 105. Increasing pH sensitivity with gate voltage is revealed for certain source-drain currents of pH-sensors based on Si NW FETs. The noise characteristic index decreases from 1.1 to 0.7 with the growth of the liquid gate voltage. Noise behavior is successfully explained in the framework of the correlated number-mobility unified fluctuation model. pH sensitivity increases as a result of the increase in liquid gate voltage, thus giving the opportunity to measure very low proton concentrations in the electrolyte medium at certain values of the liquid gate voltage.

  7. Detection of Hydroxychloroquine Retinal Toxicity by Automated Perimetry in 60 Rheumatoid Arthritis Patients With Normal Fundoscopic Findings

    OpenAIRE

    Motarjemizadeh, Qader; Aidenloo, Naser Samadi; Abbaszadeh, Mohammad

    2015-01-01

    Hydroxychloroquine (HCQ) is an antimalarial drug used extensively in treatment of autoimmune diseases such as rheumatoid arthritis. Retinal toxicity is the most important side effects of this drug. Even after the drug is discontinued, retinal degeneration from HCQ can continue to progress. Consequently, multiple ophthalmic screening tests have been developed to detect early retinopathy. The aim of the current study was to evaluate the value of central 2-10 perimetry method in early detection ...

  8. AIR FLOW AND ENVIRONMENTAL WIND VISUALIZATION USING A CW DIODE PUMPED FREQUENCY DOUBLED Nd:YAG Laser

    Directory of Open Access Journals (Sweden)

    Mircea UDREA

    2009-09-01

    Full Text Available Preliminary results obtained in developing a visualisation technique for non-invasive analysis of air flow inside INCAS subsonic wind tunnel and its appendages are presented. The visualisation technique is based on using a green light sheet generated by a continuous wave (cw longitudinally diode pumped and frequency doubled Nd:YAG laser. The output laser beam is expanded on one direction and collimated on rectangular direction. The system is tailored to the requirements of qualitative analysis and vortex tracking requirements inside the INCAS 2.5m x 2.0m subsonic wind tunnel test section, for measurements performed on aircraft models. Also the developed laser techniques is used for non-invasive air flow field analysis into environmental facilities settling room (air flow calming area. Quantitative analysis is enabled using special image processing tools upon movies and pictures obtained during the experiments. The basic experimental layout in the wind tunnel takes advantage of information obtained from the investigation of various aircraft models using the developed visualisation technique. These results are further developed using a Particle Imaging Velocimetry (PIV experimental technique.The focus is on visualisation techniques to be used for wind flow characterization at different altitudes in indus-trial and civil buildings areas using a light sheet generated by a Nd:YAG cw pumped and doubled laser at 532 nm wave-length. The results are important for prevention of biological/chemical disasters such as spreading of extremely toxic pol-lutants due to wind. Numerical simulations of wind flow and experimental visualisation results are compared. A good agreement between these results is observed.

  9. Perimetria azul-amarelo em usuários de tabaco-álcool Blue-on-yellow perimetry in tobacco and alcohol consumers

    Directory of Open Access Journals (Sweden)

    José Fernando de Carvalho Júnior

    2006-10-01

    Full Text Available OBJETIVO: Avaliar as alterações de campo visual em usuários crônicos de tabaco e álcool por meio da perimetria azul-amarelo estratégia 10-2. MÉTODOS: Quarenta e dois olhos de vinte e um voluntários usuários de tabaco e álcool, todos do gênero masculino, foram selecionados após exame oftalmológico completo e normal, sendo submetidos a perimetria azul-amarelo estratégia 10-2. Quinze voluntários participaram do grupo controle. A análise dos dados foi realizada mediante gráfico da profundidade do defeito e número de pontos alterados. RESULTADOS: Observou-se que 40 olhos (95,3% dos usuários crônicos de tabaco e álcool, apresentaram maior freqüência de alterações no gráfico de profundidade do defeito (>10dB e 27 olhos (64,3% apresentaram número de pontos alterados (>10 pontos, (pPURPOSE: To evaluate the visual field changes in blue-on-yellow perimetry (B/Y strategy 10-2 in alcohol and tobacco smoking consumers. METHODS: Forty-two eyes of twenty-one users were studied. Fifteen individuals were used as a control group. All volunteers were males. After normal ophthalmologic examinations, central 10-2 (B/Y was performed in both eyes. Analysis of the results was performed through the alterations in the depth graph defect and number of altered points. RESULTS: It was found that the majority of the chronic alcohol and tobacco smoking consumers had a greater frequency of alterations in the depth graph defect; 40 eyes (95.3%, (>10dB, and 27 eyes (64.3% showed a number of altered points, (>10 points, (p<0.0001. All those who were used as a control group showed alterations in the depth graph defect and number of altered points, but had less than 10dB and 10 altered points, respectively. CONCLUSION: A higher number of abnormal points and depth graph defects and number of altered points were observed in alcohol and tobacco smoking consumers reflecting a higher number of alterations in the cells of the parvocellular system, responsible

  10. Modulated Pulse Generations in a Laser-diode-pumped Passively Q-switched Intracavity-frequency-doubling Nd∶YVO4 Laser

    Institute of Scientific and Technical Information of China (English)

    郑加安; 赵圣之; 陈磊

    2002-01-01

    The investigative results of modulated pulse output from an LD end-pumped passively Q-switched intracavity-frequency-doubling Nd∶YVO4/KTP laser with Cr4+∶YAG saturable absorber are presented. The numerical stimulations of these modulated pulses are carried out basing on the rate equations. It indicated that the modulations are attribute to the frequency beating of two eigenstates of the resonant polarized modes. The theoretical calculations are in good agreement with the experimental observations.

  11. Low and high-frequency TENS in post-episiotomy pain relief: a randomized, double-blind clinical trial

    Directory of Open Access Journals (Sweden)

    Ana C. R. Pitangui

    2014-01-01

    Full Text Available Objective: To evaluate the effectiveness of low-frequency TENS (LFT and high-frequency TENS (HFT in post-episiotomy pain relief. Method: A randomized, controlled, double-blind clinical trial with placebo composed of 33 puerperae with post-episiotomy pain. TENS was applied for 30 minutes to groups: HFT(100 Hz; 100 µs, LFT (5 Hz; 100 µs, and placebo (PT. Four electrodes were placed in parallel near the episiotomy and four pain evaluations were performed with the numeric rating scale. The first and the second evaluation took place before TENS application and immediately after its removal and were done in the resting position and in the activities of sitting and ambulating. The third and fourth evaluation took place 30 and 60 minutes after TENS removal, only in the resting position. Intragroup differences were verified using the Friedman and Wilcoxon tests, and the intergroup analysis employed the Kruskal-Wallis test. Results: In the intragroup analysis, there was no significant difference in the PT during rest, sitting, and ambulation (P>0.05. In the HFT and LFT, a significant difference was observed in all activities (P<0.001. In the intergroup analysis, there was a significant difference in the resting position in the HFT and LFT (P<0.001. In the sitting activity, a significant difference was verified in the second evaluation in the HFT and LFT (P<0.008. No significant difference was verified among the groups in ambulation (P<0.20. Conclusions: LFT and HFT are an effective resource that may be included in the routine of maternity wards.

  12. Cooperative Transmission in Mobile Wireless Sensor Networks with Multiple Carrier Frequency Offsets: A Double-Differential Approach

    Directory of Open Access Journals (Sweden)

    Kun Zhao

    2014-01-01

    Full Text Available As a result of the rapidly increasing mobility of sensor nodes, mobile wireless sensor networks (MWSNs would be subject to multiple carrier frequency offsets (MCFOs, which result in time-varying channels and drastically degrade the network performance. To enhance the performance of such MWSNs, we propose a relay selection (RS based double-differential (DD cooperative transmission scheme, termed RSDDCT, in which the best relay sensor node is selected to forward the source sensor node’s signals to the destination sensor node with the detect-and-forward (DetF protocol. Assuming a Rayleigh fading environment, first, exact closed-form expressions for the outage probability and average bit error rate (BER of the RSDDCT scheme are derived. Then, simple and informative asymptotic outage probability and average BER expressions at the large signal-to-noise ratio (SNR regime are presented, which reveal that the RSDDCT scheme can achieve full diversity. Furthermore, the optimum power allocation strategy in terms of minimizing the average BER is investigated, and simple analytical solutions are obtained. Simulation results demonstrate that the proposed RSDDCT scheme can achieve excellent performance over fading channels in the presence of unknown random MCFOs. It is also shown that the proposed optimum power allocation strategy offers substantial average BER performance improvement over the equal power allocation strategy.

  13. Second-order Scattering and Frequency Doubling Scattering Spectra of Thallium(III)-Methotrexate System and Its Analytical Application

    Institute of Scientific and Technical Information of China (English)

    XI Cun-Xian; LIU Zhong-Fang; HU Xiao-Li; LIU Shao-Pu; DUAN Hui

    2008-01-01

    In pH 4.9 Britton-Robinson buffer solution,methotrexate (MTX) reacted with thallium(III) to form a 3:1 che late.This resulted in great enhancement of second-order scattering (SOS) spectra and frequency doubling scattering (FDS) spectra and appearance of new SOS and FDS spectra.Their maximum wavelengths were located at 520 and 390 nm,respectively.The increments of scattering intensities (ΔI) were directly proportional to the concentrations of MTX in the ranges of 0.022--2.0 μg·mL-1 (SOS method) and 0.008--2.5μg·mL-1 (FDS method).The methods exhibited high sensitivities.The detection limits for MTX were 7.4 ng·mL-1 (SOS method) and 2.3 ng.mL-1 (FDS method),respectively.The optimum conditions of the reaction,the influencing factors and the effects of coexisting substances were investigated.A highly sensitive,simple and fast method for the determination of MTX has been developed.The method can be applied satisfactorily to the determination of MTX in human serum samples.In this work,the charge distribution of MTX was calculated by a CNDO quantum chemistry method.In addition,the reaction mechanism was discussed.

  14. High Power Diode-End-Pumped Nd:YAG 946-nm Laser and Its Efficient Frequency Doubling

    Institute of Scientific and Technical Information of China (English)

    ZHOU Rui; ZHAO Shi-Yong; CAI Zhi-Qiang; ZHANG Qiang; WEN Wu-Qi; DING Xin; WANG Peng; DING Li-Li; YAO Jian-Quan

    2005-01-01

    @@ We report a high power operation of the 4F3/2 → 4I9/2 transition in diode-end-pumped laser at 946nm. The maximum output of5.1 W is obtained with a short linear plano-concave cavity, and the slope efficiency is 24.5%at incident pump power of 23.3 W. To our knowledge, this is the highest value of the LD-pumped Nd:YAG 946nm lasers that employ the conversional Nd:YAG rod as the gain medium. By intracavity frequency doubling with an LBO crystal, up to 982mW cw output power in the blue spectral range at 473nm is achieved at an incident pump power of 10.9 W with a compact three-element cavity, leading to optical-to-optical conversion efficiency of 9%. The conversion efficiency should be increased to 15.1%, if the rather low absorption coefficient of this Nd:YAG is considered.

  15. Frequency-dependent Study of Ultrapure Solid 4He by Using Rigid Double-pendulum Torsional Oscillator

    Science.gov (United States)

    Choi, Jaewon; Shin, Jaeho; Kim, Eunseong

    2015-03-01

    The physical origin of the period drop found in the torsional oscillator (TO) containing solid 4He was previously interpreted as the appearance of supersolidity. The current consensus is that the increase in the shear modulus leads to the period anomaly. Further studies show that the stiffening effect in TO can be amplified if a TO is not properly designed to be ``rigid.'' In this study, we designed a rigid double-pendulum TO. High purity solid 4He sample (0.6ppb) was grown by the block capillary method. The resonant period of TO starts to decrease from the empty cell data at 80mK. The ratio of the resonant period changes to the total mass loading are 3 . 8 ×10-5 and 2 . 6 ×10-4 for 1st and 2nd mode, respectively. Unlike recent experiment, we could not found a frequency-independent period drop. The upper bound for the putative supersolid fraction is less than 4 ×10-6 . The dissipation peak accompanied with the period drop was also analyzed with Cole-Cole plot and ωτ plot. We conclude that major contribution for the anomalous TO responses comes from the elastic effect.

  16. Design and Operation of a Frequency Doubled Nd:YAG Thomson Scattering System with Transmission Grating ICCD Spectrometer

    Science.gov (United States)

    Schoenbeck, N. L.; Dowd, A. S.; Fonck, R. J.; Schlossberg, D. J.; Winz, G. R.

    2012-10-01

    A novel Thomson scattering system has been deployed on the Pegasus Toroidal Experiment. It provides a relatively low-cost, simplified design. Scattering is achieved using a 7 ns, 2 J frequency doubled Nd:YAG laser operating at 532 nm. The laser focuses to ˜3 mm diameter within the plasma via a 7 m beam-line. The beam-line contains cameras as beam finders and remotely adjustable mirrors for shot-to-shot alignment. A custom multi-element lens collects scattered photons from 15 cm 40%) image intensified CCD (ICCD) camera. Three spectrometers provide a total of 24 channels. Two interchangeable gratings exist to cover low (Te = 10--100 eV) and high (Te = 0.10--1 keV) electron temperature regimes on Pegasus. The spectrometer is optimized for ne from mid-10^18 to mid-10^19 m-3. The signal-to-noise expected is ˜0.5 of an equivalent system using Nd:YAG at 1064 nm and avalanche photodiode detectors.

  17. Study on Frequency Doubling Scattering and Second—Order Scattering Spectra of Heparin—Methylene Blue System

    Institute of Scientific and Technical Information of China (English)

    刘绍璞; 罗红群; 李念兵; 刘忠芳

    2003-01-01

    Binding of heparin with methylene blue(MB) in pH5.7 Britton-Robinson buffer can result in a significant enhancement of frequency doubling scattering (FDS) and second-order scattering (SOS).Their maximum scattering wavelengths(λmax) appear at 350nm for FDS and 700nm for SOS,respectively.The optimum conditions of the reaction,the influencing factors and the relationship between the two scattering intensities and the concentration of heparin have been investigated.The new methods for the determination of trace amounts of heparin bassed on the FDS and SOS methods have been developed,which exhibit high sensitivities.The detection limits of heparin are 4.36ng/mL for the FDS method and 3.55ng/mL for the SOS method,respectively.Both of the methods have fairly godd selectivity and ware applied to the determination of heparin in sodium heparinate injection samples with satisfactory results.Moreover,the relative mechamisms have also been discussed.

  18. One-shot and aberration-tolerable homodyne detection for holographic storage readout through double-frequency grating-based lateral shearing interferometry.

    Science.gov (United States)

    Yu, Yeh-Wei; Xiao, Shuai; Cheng, Chih-Yuan; Sun, Ching-Cherng

    2016-05-16

    A simple method to decode the stored phase signal of volume holographic data storage with adequate wave aberration tolerance is highly demanded. We proposed and demonstrated a one-shot scheme to decode a binary-phase encoding signal through double-frequency-grating based shearing interferometry (DFGSI). The lateral shearing amount is dependent on the focal length of the collimated lens and the frequency difference between the gratings. Diffracted waves with phase encoding were successfully decoded through experimentation. An optical model for the DFGSI was built to analyze phase-error induction and phase-difference control by shifting the double-frequency grating longitudinally and laterally, respectively. The optical model was demonstrated experimentally. Finally, a high aberration tolerance of the DFGSI was demonstrated using the optical model.

  19. Focus: Two-dimensional electron-electron double resonance and molecular motions: The challenge of higher frequencies

    Science.gov (United States)

    Franck, John M.; Chandrasekaran, Siddarth; Dzikovski, Boris; Dunnam, Curt R.; Freed, Jack H.

    2015-06-01

    The development, applications, and current challenges of the pulsed ESR technique of two-dimensional Electron-Electron Double Resonance (2D ELDOR) are described. This is a three-pulse technique akin to 2D Exchange Nuclear Magnetic Resonance, but involving electron spins, usually in the form of spin-probes or spin-labels. As a result, it required the extension to much higher frequencies, i.e., microwaves, and much faster time scales, with π/2 pulses in the 2-3 ns range. It has proven very useful for studying molecular dynamics in complex fluids, and spectral results can be explained by fitting theoretical models (also described) that provide a detailed analysis of the molecular dynamics and structure. We discuss concepts that also appear in other forms of 2D spectroscopy but emphasize the unique advantages and difficulties that are intrinsic to ESR. Advantages include the ability to tune the resonance frequency, in order to probe different motional ranges, while challenges include the high ratio of the detection dead time vs. the relaxation times. We review several important 2D ELDOR studies of molecular dynamics. (1) The results from a spin probe dissolved in a liquid crystal are followed throughout the isotropic → nematic → liquid-like smectic → solid-like smectic → crystalline phases as the temperature is reduced and are interpreted in terms of the slowly relaxing local structure model. Here, the labeled molecule is undergoing overall motion in the macroscopically aligned sample, as well as responding to local site fluctuations. (2) Several examples involving model phospholipid membranes are provided, including the dynamic structural characterization of the boundary lipid that coats a transmembrane peptide dimer. Additionally, subtle differences can be elicited for the phospholipid membrane phases: liquid disordered, liquid ordered, and gel, and the subtle effects upon the membrane, of antigen cross-linking of receptors on the surface of plasma membrane

  20. Focus: Two-dimensional electron-electron double resonance and molecular motions: The challenge of higher frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Franck, John M.; Chandrasekaran, Siddarth; Dzikovski, Boris; Dunnam, Curt R.; Freed, Jack H., E-mail: jhf3@cornell.edu [Department of Chemistry and Chemical Biology and National Biomedical Center for Advanced ESR Technology, Cornell University, Ithaca, New York 14853 (United States)

    2015-06-07

    The development, applications, and current challenges of the pulsed ESR technique of two-dimensional Electron-Electron Double Resonance (2D ELDOR) are described. This is a three-pulse technique akin to 2D Exchange Nuclear Magnetic Resonance, but involving electron spins, usually in the form of spin-probes or spin-labels. As a result, it required the extension to much higher frequencies, i.e., microwaves, and much faster time scales, with π/2 pulses in the 2-3 ns range. It has proven very useful for studying molecular dynamics in complex fluids, and spectral results can be explained by fitting theoretical models (also described) that provide a detailed analysis of the molecular dynamics and structure. We discuss concepts that also appear in other forms of 2D spectroscopy but emphasize the unique advantages and difficulties that are intrinsic to ESR. Advantages include the ability to tune the resonance frequency, in order to probe different motional ranges, while challenges include the high ratio of the detection dead time vs. the relaxation times. We review several important 2D ELDOR studies of molecular dynamics. (1) The results from a spin probe dissolved in a liquid crystal are followed throughout the isotropic → nematic → liquid-like smectic → solid-like smectic → crystalline phases as the temperature is reduced and are interpreted in terms of the slowly relaxing local structure model. Here, the labeled molecule is undergoing overall motion in the macroscopically aligned sample, as well as responding to local site fluctuations. (2) Several examples involving model phospholipid membranes are provided, including the dynamic structural characterization of the boundary lipid that coats a transmembrane peptide dimer. Additionally, subtle differences can be elicited for the phospholipid membrane phases: liquid disordered, liquid ordered, and gel, and the subtle effects upon the membrane, of antigen cross-linking of receptors on the surface of plasma membrane

  1. Expansion of lower-frequency locally resonant band gaps using a double-sided stubbed composite phononic crystals plate with composite stubs

    Energy Technology Data Exchange (ETDEWEB)

    Li, Suobin; Chen, Tianning [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Wang, Xiaopeng, E-mail: xpwang@mail.xjtu.edu.cn [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Li, Yinggang [Key Laboratory of High Performance Ship Technology of Ministry of Education, Wuhan University of Technology, Wuhan, 430070 (China); Chen, Weihua [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China)

    2016-06-03

    We studied the expansion of locally resonant complete band gaps in two-dimensional phononic crystals (PCs) using a double-sided stubbed composite PC plate with composite stubs. Results show that the introduction of the proposed structure gives rise to a significant expansion of the relative bandwidth by a factor of 1.5 and decreases the opening location of the first complete band gap by a factor of 3 compared to the classic double-sided stubbed PC plate with composite stubs. Furthermore, more band gaps appear in the lower-frequency range (0.006). These phenomena can be attributed to the strong coupling between the “analogous rigid mode” of the stub and the anti-symmetric Lamb modes of the plate. The “analogous rigid mode” of the stub is produced by strengthening the localized resonance effect of the composite plates through the double-sided stubs, and is further strengthened through the introduction of composite stubs. The “analogous rigid mode” of the stubs expands the out-of-plane band gap, which overlaps with in-plane band gap in the lower-frequency range. As a result, the complete band gap is expanded and more complete band gaps appear. - Highlights: • Expansion of lower-frequency locally resonant BGs using novel composite phononic crystals plates. • The proposed structure expands the relative bandwidth 1.5 times compared to classic doubled-sided stubbed PC plates. • The opening location of the first complete BG decreases 3 times compared to the classic doubled-sided stubbed PC plates. • The concept “analogous rigid mode” is put forward to explain the expansion of lower-frequency BGs.

  2. Objective VEP perimetry in glaucoma: asymmetry analysis to identify early deficits.

    Science.gov (United States)

    Graham, S L; Klistorner, A I; Grigg, J R; Billson, F A

    2000-02-01

    The multifocal visual evoked potential (VEP) shows markedly symmetrical responses between the two eyes of control subjects. Patients with glaucoma and patients considered at high risk for glaucoma were examined to determine if VEP asymmetry could be identified and used for diagnosis and detection of early damage. Multifocal pattern VEP recordings were performed using a single channel bipolar occipital electrode position and the Visual Evoked Response Imaging System (VERIS). There were 125 subjects: 24 control subjects, 70 patients with glaucoma, and 31 patients considered at high risk for glaucoma. A between-eye relative asymmetry coefficient (RAC) was determined for each of the 60 test points in the VEP field. The RAC for patients with glaucoma and patients considered at risk for glaucoma were compared with values from control subjects. Correlation between Humphrey thresholds and RAC scores was performed. Patients with glaucoma and patients considered at risk for glaucoma both showed significantly larger mean quadrant RAC values. When point by point analysis was performed, 69 out of 70 scotomas were identified with a cluster of at least 3 points of P < 0.05. For those considered at high risk for glaucoma, 10 out of 31 patients had abnormal areas in the VEP field. There was a strong correlation (r = 0.82) between quadrantic RAC mean values and Humphrey quadrant threshold scores in an asymmetric glaucoma subgroup. Abnormal VEP responses were identified in parts of the visual field that were still normal on perimetry. Asymmetry analysis correctly identifies patients with glaucomatous field loss and shows abnormalities in many patients considered at high risk for glaucoma who still have normal fields. Asymmetry analysis is able to identify objectively the extent of glaucomatous damage and may be able to detect changes before subjective field loss occurs.

  3. Detection of Hydroxychloroquine Retinal Toxicity by Automated Perimetry in 60 Rheumatoid Arthritis Patients with Normal Fundoscopic Findings.

    Science.gov (United States)

    Motarjemizadeh, Qader; Aidenloo, Naser Samadi; Abbaszadeh, Mohammad

    2015-06-25

    Hydroxychloroquine (HCQ) is an antimalarial drug used extensively in treatment of autoimmune diseases such as rheumatoid arthritis. Retinal toxicity is the most important side effects of this drug. Even after the drug is discontinued, retinal degeneration from HCQ can continue to progress. Consequently, multiple ophthalmic screening tests have been developed to detect early retinopathy. The aim of the current study was to evaluate the value of central 2-10 perimetry method in early detection of retinal toxicity. This prospective cross-sectional investigation was carried out on 60 rheumatoid arthritis patients, who had been receiving HCQ for at least 6 months and still were on their medication (HCQ intake) at the time of enrollment. An ophthalmologist examined participants using direct and indirect ophthalmoscopy. Visual field testing with automated perimetry technique (central 2-10 perimetry with red target) was performed on all included subjects twice in 6 months interval: The first one at the time of enrollment and the second one 6 months later. Males and females did not show any significant difference in terms of age, duration of therapy, daily and cumulative HCQ dose, anterior or posterior segment abnormalities, hypertension, body mass index, and best corrected visual acuity. Anterior segment was abnormal in 9 individuals including 3 subjects with macular pigmentary changes, 4 individuals with cataract and 2 cases with dry eyes. Moreover, 12 subjects had retinal pigmented epithelium (RPE) in their posterior segments. After 6 months, depressive changes appeared in 12 subjects. Additionally, HCQ therapy worsened significantly the perimetric results of 5 (55.6%) patients with abnormal anterior segment. A same trend was observed in perimetric results of 6 (50.0%) subjects with abnormal posterior segments (P=0.009). The daily dose of HCQ (P=0.035) as well as the cumulative dose of hydroxychloroquine (P=0.021) displayed statistically significant associations with

  4. 6.2-W deep blue light generation by intracavity frequency-doubled Nd:GdVO4 using BiBO

    Institute of Scientific and Technical Information of China (English)

    Yanfei Lü; Xihe Zhang; Zhihai Yao; Fengdong Zhang

    2007-01-01

    @@ Efficient continuous-wave (CW) intracavity frequency doubling of a diode-end-pumped Nd:GdVO4 laser operating on 4F3/2 - 4I9/2 transitions at 912 nm has been demonstrated. A symmetrical cavity with two laser rods is designed, which divides the pump power between the two laser rods, allowing for greater power scalability. An 18-mm-long BiBO crystal, cut for critical type Ⅰ phase matching, is used for the intracavity frequency-doubled laser. A maximum output power of 6.2 W in the blue spectral range at 456 nm has been achieved with the pump power of 36 W. The beam quality M2 value is 2.5 in both horizontal and vertical directions. The ellipticity of the deep blue laser is 0.98, and the power stability is better than 3.2% at the maximum output power.

  5. Low-Frequency Fatigue Assessed as Double to Single Twitch Ratio after Two Bouts of Eccentric Exercise of the Elbow Flexors.

    Science.gov (United States)

    Janecki, Damian; Jaskólska, Anna; Marusiak, Jarosław; Jaskólski, Artur

    2016-12-01

    The aim of this study was to assess low-frequency fatigue as a double to single twitch ratio after repeated eccentric exercise of the elbow flexors. Maximal isometric torque, single and double twitch responses and low-frequency fatigue were assessed on the elbow flexors in 16 untrained male volunteers before, immediately after, 24 and 48 hours following two bouts of eccentric exercise consisted of 30 repetitions of lowering a dumbbell adjusted to ~75% of each individual's maximal isometric torque. Maximal isometric torque and electrically evoked responses decreased significantly in all measurements after the first bout of eccentric exercise (p single twitch ratio could be used as a sensitive tool in the evaluation of muscle recovery and adaptation to repeated eccentric exercise.

  6. Evaluation of Optical Properties of Self-Frequency-Doubling Crystal Yb:GdYAl3(BO3)4 for Laser Applications

    Institute of Scientific and Technical Information of China (English)

    LI Jing; LI Qiang; WANG Ji-Yang; ZHAO Hong-Yang

    2007-01-01

    @@ Yb:GdYAl3(BO3)4(Yb:GdYAB) is investigated as a new laser crystal for potential applications in self-frequency doubling. The emission and absorption properties of Yb:GdYAB crystal are studied, and the emission decay times of the upper laser level are measured. The emission cross sections are evaluated using the absorption cross section and principle of reciprocity. The other laser performance parameters, such as the minimum inversion fraction βmin, pump saturation intensity Isat and minimum pump intensity Imin, are also calculated. The results are discussed in the framework of requirements for an effective diode-pumped Yb3+ laser system. Yb:GdYAB is expected to exhibit the most useful laser properties and to be superior to Yb:YAB crystal that has been excellent self-frequency-doubling crystal at present in many key spectroscopic parameter values.

  7. LD side-pumped intracavity frequency-doubled high power Nd:YAG green laser based on acousto-optic Q-switch

    Institute of Scientific and Technical Information of China (English)

    ZHANG Feng-chuan; FAN Xiu-wei; XUE Lin; CHAI Hong-liang; HE Jing-liang

    2006-01-01

    A highly efficient and high power green laser generated by intracavity frequency doubling of a diode-side pumped Q-switched Nd:YAG laser has been demonstrated. In the simple L-shaped cavity geometry,the maximum green output power of 28.5 W was obtained with a pulse width of 95 ns at a pulse repetition rate of 10 kHz by using a LBO crystal for frequency doubling,corresponding to a conversion efficiency of 11% from diode pump power to pulse green power. At a pulse repetition rate of 1 kHz,6.9 mJ of pulse energy,25 ns of pulse duration and 276 kW of peak power were obtained.

  8. Simultaneous Q-switching and Frequency-doubling by a Single KTP Crystal in a Diode-pumped Nd: YVO4 Laser

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei; HUO Yujing; HE Shufang; FENG Lichun

    2000-01-01

    The interrelation between the phase matching condition for second harmonic generation (SHG) and the electro-optic Q-switching in KTP was numerically analyzed. A diode-pumped Q-switched Nd: YVO4/KTP green laser was reported, where the KTP crystal was simultaneously used as both an electrooptic Q-switcher and a frequency-doubling crystal in type Ⅱ phase matching.Compared with the conventional frequency-doubling and Q-switching configuration, low loss and high efficiency characteristics were realized by using a single KTP crystal. The Q-switched green laser pulse with a peak power of 762 W and a pulse width of 12 ns was obtained with 1 W pump power.

  9. Determination of Light-beam Dispersion Angle by BBO Frequency-doubling%BBO倍频法测定光束发散角

    Institute of Scientific and Technical Information of China (English)

    沙先武; 是度芳; 陈长水; 谢建平

    2000-01-01

    A new method is designed to determinate the light beam dispersion angle according to the fact that the BBO crystal has a certain phase match angle on certain light-frequencies while doubling frequency. The method is simple and more precise.%光束发散角的测定方法有多种,本文提出一种新的测定方法,利用BBO晶体倍频中的角度匹配来测定发散角,精度较高.

  10. High Current Multi-finger InGaAs/InP Double Heterojunction Bipolar Transistor with the Maximum Oscillation Frequency 253 GHz

    Institute of Scientific and Technical Information of China (English)

    JIN Zhi; SU Yong-bo; CHENG Wei; LIU Xin-Yu; XU An-Huai; QI Ming

    2008-01-01

    @@ A four-finger InGaAs/InP double heterojunction bipolar transistor is designed and fabricated successfully by using planarization technology. The emitter area of each finger is 1 × 15 μm2. The breakdown voltage is more than 7V, the maximum collector current could be more than 100mA. The current gain cutoff frequency is as high as 155 GHz and the maximum oscillation frequency reaches 253 GHz. The heterostructure bipolar transistor can offer more than 70mW class-A maximum output power at W band and the maximum power density can be as high as 1.2 W/mm.

  11. Thermal birefringence-compensated linear intracavity frequency doubled Nd:YAG rod laser with 73 ns pulse duration and 160Wgreen output power

    Indian Academy of Sciences (India)

    S K Sharma; A J Singh; P K Gupta; P Hedaoo; P K Mukhopadhyay; K Ranganathan; K S Bindra; S M Oak

    2014-02-01

    In a thermally birefringence-compensated linear cavity configuration, ∼160 W of average green power by intracavity frequency doubling of AO Q-switched Nd:YAG/LBO-based laser is demonstrated. The corresponding optical to optical conversion efficiency is estimated to be ∼12.7%. The pulse repetition rate is 20 kHz with the individual pulse duration of 73 ns. The beam quality parameter is measured to be 18.

  12. Generation of 3.5W high efficiency blue-violet laser by intracavity frequency-doubling of an all-solid-state tunable Ti:sapphire laser.

    Science.gov (United States)

    Ding, X; Wang, R; Zhang, H; Wen, W Q; Huang, L; Wang, P; Yao, J Q; Yu, X Y; Li, Z

    2008-03-31

    In this paper, we report a high power, high efficiency blue-violet laser obtained by intracavity frequency-doubling of an all-solid-state Q-switched tunable Ti:sapphire laser, which was pumped by a 532 nm intracavity frequency-doubled Nd:YAG laser. A beta-BaB2O4 (BBO) crystal was used for frequency-doubling of the Ti:sapphire laser and a V-shape folded three-mirror cavity was optimized to obtain high power high efficiency second harmonic generation (SHG). At an incident pump power of 22 W, the tunable output from 355 nm to 475 nm was achieved, involving the maximum average output of 3.5 W at 400 nm with an optical conversion efficiency of 16% from the 532 nm pump laser to the blue-violet output. The beam quality factor M(2) was measured to be Mx(2)=2.15, My(2)=2.38 for characterizing the tunable blue laser.

  13. Low-Frequency Fatigue Assessed as Double to Single Twitch Ratio after Two Bouts of Eccentric Exercise of the Elbow Flexors

    Directory of Open Access Journals (Sweden)

    Damian Janecki, Anna Jaskólska, Jarosław Marusiak, Artur Jaskólski

    2016-12-01

    Full Text Available The aim of this study was to assess low-frequency fatigue as a double to single twitch ratio after repeated eccentric exercise of the elbow flexors. Maximal isometric torque, single and double twitch responses and low-frequency fatigue were assessed on the elbow flexors in 16 untrained male volunteers before, immediately after, 24 and 48 hours following two bouts of eccentric exercise consisted of 30 repetitions of lowering a dumbbell adjusted to ~75% of each individual’s maximal isometric torque. Maximal isometric torque and electrically evoked responses decreased significantly in all measurements after the first bout of eccentric exercise (p < 0.05. In measurements performed at 24 and 48 hours after the second bout both maximal voluntary isometric torque and electrically evoked contractions were significantly higher than in measurements performed after the first bout (p < 0.05. Although low-frequency fatigue significantly increased up to 48 hours after each bout of eccentric exercise, its values at 24 and 48 hours after the second bout were significantly lower than at respective time points after the first bout (p < 0.05. Double to single twitch ratio could be used as a sensitive tool in the evaluation of muscle recovery and adaptation to repeated eccentric exercise.

  14. Frequency and zero-point vibrational energy scale factors for double-hybrid density functionals (and other selected methods): can anharmonic force fields be avoided?

    Science.gov (United States)

    Kesharwani, Manoj K; Brauer, Brina; Martin, Jan M L

    2015-03-05

    We have obtained uniform frequency scaling factors λ(harm) (for harmonic frequencies), λ(fund) (for fundamentals), and λ(ZPVE) (for zero-point vibrational energies (ZPVEs)) for the Weigend-Ahlrichs and other selected basis sets for MP2, SCS-MP2, and a variety of DFT functionals including double hybrids. For selected levels of theory, we have also obtained scaling factors for true anharmonic fundamentals and ZPVEs obtained from quartic force fields. For harmonic frequencies, the double hybrids B2PLYP, B2GP-PLYP, and DSD-PBEP86 clearly yield the best performance at RMSD = 10-12 cm(-1) for def2-TZVP and larger basis sets, compared to 5 cm(-1) at the CCSD(T) basis set limit. For ZPVEs, again, the double hybrids are the best performers, reaching root-mean-square deviations (RMSDs) as low as 0.05 kcal/mol, but even mainstream functionals like B3LYP can get down to 0.10 kcal/mol. Explicitly anharmonic ZPVEs only are marginally more accurate. For fundamentals, however, simple uniform scaling is clearly inadequate.

  15. Patients double-seropositive for ANCA and anti-GBM antibodies have varied renal survival, frequency of relapse, and outcomes compared to single-seropositive patients.

    Science.gov (United States)

    McAdoo, Stephen P; Tanna, Anisha; Hrušková, Zdenka; Holm, Lisa; Weiner, Maria; Arulkumaran, Nishkantha; Kang, Amy; Satrapová, Veronika; Levy, Jeremy; Ohlsson, Sophie; Tesar, Vladimir; Segelmark, Mårten; Pusey, Charles D

    2017-09-01

    Co-presentation with both ANCA and anti-GBM antibodies is thought to be relatively rare. Current studies of such 'double-positive' cases report small numbers and variable outcomes. To study this further we retrospectively analyzed clinical features and long-term outcomes of a large cohort of 568 contemporary patients with ANCA-associated vasculitis, 41 patients with anti-GBM disease, and 37 double-positive patients with ANCA and anti-GBM disease from four European centers. Double-positive patients shared characteristics of ANCA-associated vasculitis (AAV), such as older age distribution and longer symptom duration before diagnosis, and features of anti-GBM disease, such as severe renal disease and high frequency of lung hemorrhage at presentation. Despite having more evidence of chronic injury on renal biopsy compared to patients with anti-GBM disease, double-positive patients had a greater tendency to recover from being dialysis-dependent after treatment and had intermediate long-term renal survival compared to the single-positive patients. However, overall patient survival was similar in all three groups. Predictors of poor patient survival included advanced age, severe renal failure, and lung hemorrhage at presentation. No single-positive anti-GBM patients experienced disease relapse, whereas approximately half of surviving patients with AAV and double-positive patients had recurrent disease during a median follow-up of 4.8 years. Thus, double-positive patients have a truly hybrid disease phenotype, requiring aggressive early treatment for anti-GBM disease, and careful long-term follow-up and consideration for maintenance immunosuppression for AAV. Since double-positivity appears common, further work is required to define the underlying mechanisms of this association and define optimum treatment strategies. Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

  16. Double modulation of X radiation diffracted in a quartz single crystal by high and low frequency acoustic waves

    CERN Document Server

    Kocharyan, L A; Bornazyan, H S

    1986-01-01

    The time dependence of X radiation diffracted in a quartz single crystal is experimentally investigated when surface acoustic waves modulated by low frequency oscillations of different frequencies and forms are excited in the crystal.

  17. Double relaxation phenomena of associated binary polar liquid mixture in non-polar solvent under high frequency electric field

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, S. [Department of Electronics and Instrumentation Engg (India)], E-mail: swapansit@yahoo.co.in; Sit, S.K. [Department of Physics, Dr. Meghnad Saha Institute of Technology, Debhog, Haldia, Purba Medinipore, West Bengal 721657 (India)

    2009-06-25

    Double relaxation times {tau}{sub 2} and {tau}{sub 1} due to whole molecular rotation and the flexible parts of the binary polar liquid mixture (jk) 3-bromoaniline and 1-propanol dissolved in non-polar solvent (i) benzene were estimated in terms of measured real {chi}{sup '}{sub ijk}, imaginary {chi}{sup ''}{sub ijk} parts of complex high frequency orientational susceptibility {chi}{sub ijk}{sup *} and {chi}{sub 0ijk} which is real at 20, 30, 40 and 47 deg. C experimental temperatures for 0.0, 0.25, 0.50,0.75 and 1.00 mole fractions x{sub j}'s of 1-propanol under 9.1 GHz electric field. The slopes {omega}({tau}{sub 2} + {tau}{sub 1}) and intercepts {omega}{sup 2}{tau}{sub 2}{tau}{sub 1} of the analytical straight line equations used to estimate {tau}{sub 2} and {tau}{sub 1} were derived from Bergmann's equation [U. Saha, S.K. Sit, R.C. Basak, S. Acharyya, J. Phys. D: Appl. Phys. 27 (1994) 596] based on two Debye type dispersion model of binary polar mixture. The systems 3-bromoaniline in C{sub 6}H{sub 6} and 1-propanol in C{sub 6}H{sub 6} show {tau}{sub 2} and {tau}{sub 1} only at 47 deg. C temperature like 3-bromoaniline + 1-propanol in C{sub 6}H{sub 6} at 20 and 47 deg. C temperatures for 0.25 and 0.50 mole fractions x{sub j}'s of 1-propanol. The binary polar mixture for x{sub j} = 0.75 of 1-propanol is an exception exhibiting double relaxation times at all the experimental temperatures. The relative contributions c{sub 1} and c{sub 2} due to {tau}{sub 1} and {tau}{sub 2} for eight non-rigid systems were calculated from Froehlich's equation as well as graphical plots of {chi}{sup '}{sub ijk}/{chi}{sub 0ijk}-w{sub jk} and {chi}{sup ''}{sub ijk}/{chi}{sub 0ijk}-w{sub jk} curve at w{sub jk}{yields}0. c{sub 1} and c{sub 2} are positive for Froehlich's method whereas most of the c{sub 2}'s are negative for graphical method. The dipole moments {mu}{sub 2} and {mu}{sub 1} for all the systems are calculated from

  18. Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

    Science.gov (United States)

    Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

  19. Quasi-continuous-wave 589-nm radiation based on intracavity frequency-doubled Nd:GGG/BaWO4 Raman laser

    Science.gov (United States)

    Liu, Yang; Liu, Zhaojun; Cong, Zhenhua; Men, Shaojie; Rao, Han; Xia, Jinbao; Zhang, Sasa; Zhang, Huaijin

    2016-07-01

    Quasi-continuous-wave (QCW) 589-nm radiation was realized based on a frequency-doubled crystalline Raman laser. The fundamental wave with macro-micro-pulse trains was generated from an acousto-optically Q-switched QCW diode side-pumped Nd:GGG laser. Intracavity Raman conversion was accomplished by a BaWO4 crystal and the second harmonic generation was finished by a KTP crystal. Under a pumping power of 126.0 W with a macro-pulse frequency of 300 Hz and duration of 300 μs, the maximum 589 nm output power of 4.2 W was obtained at a micro-pulse frequency of 33.3 kHz. The micro-pulse width was 13.6 ns.

  20. A dual-mode microwave resonator for double electron-electron spin resonance spectroscopy at W-band microwave frequencies

    Science.gov (United States)

    Tkach, Igor; Sicoli, Giuseppe; Höbartner, Claudia; Bennati, Marina

    2011-04-01

    We present a dual-mode resonator operating at/near 94 GHz (W-band) microwave frequencies and supporting two microwave modes with the same field polarization at the sample position. Numerical analysis shows that the frequencies of both modes as well as their frequency separation can be tuned in a broad range up to GHz. The resonator was constructed to perform pulsed ELDOR experiments with a variable separation of "pump" and "detection" frequencies up to Δ ν = 350 MHz. To examine its performance, test ESE/PELDOR experiments were performed on a representative biradical system.

  1. Near-diffraction-limited green source by frequency doubling of a diode-stack pumped Q-switched Nd:YAG slab oscillator-amplifier system.

    Science.gov (United States)

    Zhang, Hengli; Liu, Xiaomeng; Li, Daijun; Shi, Peng; Schell, Alex; Haas, Claus Rüdige; Du, Keming

    2007-09-10

    A near-diffraction-limited, stable, 18 mJ green source with a pulse width of 16.7 ns was generated at a 1 kHz repetition rate by frequency doubling of diode stacks end-pumped electro-optically Q-switched slab Nd:YAG oscillator-amplifier system. The pump to green optical conversion efficiency was 10.7%. At the output energy of 15 mJ at 532 nm, the M2 factors were 1.3 and 1.7 in the unstable and stable directions, respectively. The energy pulse stability was approximately 0.8%.

  2. 软X射线双频光栅剪切干涉法研究%Studies on soft X-ray shearing interferometry with double-frequency gratings∗

    Institute of Scientific and Technical Information of China (English)

    刘正坤; 邱克强; 陈火耀; 刘颖; 徐向东; 付绍军; 王琛; 安红海; 方智恒

    2013-01-01

    The M-Z interferometer with gratings or multilayer mirrors is widely used in the X-ray laser plasma diagnoses; however, this system is difficult to adjust, and results in the low success rate in experiment. Since wavefront shearing interferometers do not need a separate reference wavefront, they have inherent advantages compared with conventional interferometers. But the absence of shearing element for soft X-ray has restrained the application of the shearing interferometry in soft X-ray measurement. In this paper, a new-structured double-frequency grating was proposed and fabricated that served as the shearing element for soft X-rays, which can promote the application of shearing interferometers in the X-ray laser plasma diagnoses. The diffraction characteristics of the double-frequency grating are analyzed and tested in the synchrotron radiation beams. It is found that the intensity ratio of the two working diffracted beams is over 75%, and the intensity ratio of the rest diffracted beam to the working beam is less than 5%. An X-ray shearing interferometer using a double-frequency grating with 1000 lines/mm and 1002.5 lines/mm gratings was set up, and a clear shear interferogram was obtained. The experimental results demonstrated that the soft X-ray shearing interferometer using double-frequency grating can be applied in the X-ray laser plasma diagnoses.%  本文中设计了一种利用软X射线双频光栅作为剪切干涉元件的剪切系统,使剪切干涉法在软X射线波段得到了应用。介绍了软X射线双频光栅的结构及衍射特性,在同步辐射光束线对双频光栅的效率分布进行了测试实验,两个剪切级次的效率比值高于75%,干扰级次效率低于5%。利用软X射线双频光栅为剪切干涉光学元件,对待测靶进行了静态检测,得到了对比度高,稳定的干涉条纹,验证了该方法在软X射线等离子体密度诊断中的可行性。

  3. 1-MW peak power, 574-kHz repetition rate picosecond pulses at 515 nm from a frequency-doubled fiber amplifier

    Science.gov (United States)

    Zou, Feng; Wang, Ziwei; Wang, Zhaokun; Bai, Yang; Li, Qiurui; Zhou, Jun

    2016-11-01

    1-MW peak power picosecond, 574-kHz repetition rate green laser at 515-nm is generated from a frequency-doubled fiber amplifier. 12-ps pulses with 13.9-μJ energy at 515 nm are achieved with a noncritically phase-matched lithium triborate (LBO) crystal through second harmonic generation of a 1030 nm infrared source. The infrared source employs ultra-large-mode-area rod-type photonic crystal fiber (Rod-PCF) for direct picosecond amplification and delivers 20-W 11.6-ps 2.97-MW pulse train with near-diffraction-limited beam quality (M2 = 1.01).

  4. THE SIX-WHEEL FRIGHT TRUCK LOCOMOTIVE OF DOUBLE DELIVERY USES RADIO-FREQUENCY TRANSFER WITH PADDING AND ASYNCHRONIZED TRACTION IMPELLENTS

    Directory of Open Access Journals (Sweden)

    M. H. Visin

    2010-10-01

    Full Text Available Our research offers a new perspective loading pattern of the 12-wheel double-feed freight electric locomotive with the asynchronous tractive motor using an adapter transformer with the high-frequency uncoupler. This will make it possible to decrease the traction-feeding transformer mass 2.3 times, to remove the current pulse advancing on the track circuit and therefore the influence on the work of the ALSE and CBS. So the railway traffic safety will be increased considerably.

  5. Experiment Study of Dual Wavelength and Dual Pulse Q-switched Intracavity Frequency Doubling of a Tunable Cr:LiSAF Laser

    Institute of Scientific and Technical Information of China (English)

    CHEN Changshui; WANG Peilin; XIE Jianping; SHI Dufang; SHA Xianwu; HE Yulong

    2001-01-01

    In this paper, a flashlamp-pumped Q-switched Cr: LiSAF laser system with intracavity frequency doubling is designed to obtain dual pulse and dual wavelength laser output. The behaviors of second harmonic output of dual pulse and dual wavelength are studied experimentally. Good results are obtained in experiments: the output energy of each second harmonic pulse a round 448.1 nm is 10.2 mJ, the dual pulse time interval can be tuned widely, and the tunable range of each second harmonic wavelength is 448.1 to 465 nm.

  6. Continuous-Wave Green Laser of 9.9W by Intracavity Frequency Doubling in Laser Diode Single-End-Pumped Nd:YVO4/LBO

    Institute of Scientific and Technical Information of China (English)

    BAI Yang; LI Long; CHEN Hao-Wei; YANG Zhi; BAI Jin-Tao

    2004-01-01

    @@ A maximum of 9.9 W cw TEM00 output at 532nm laser has been obtained by intracavity frequency doubling with LBO in laser-diode single-end-pumped Nd:YVO4. The Nd:YVO4/LBO green laser has a simple three mirror V-fold cavity structure. The optical-optical conversion efficiency was 34.8%. Based on the equation of thermal conduction, a general solution for the laser-crystal interior temperature distribution is obtained by the semi-analytical thermal analysis method.

  7. Sensitivity and specificity of machine learning classifiers for glaucoma diagnosis using Spectral Domain OCT and standard automated perimetry

    Directory of Open Access Journals (Sweden)

    Fabrício R. Silva

    2013-06-01

    Full Text Available PURPOSE: To evaluate the sensitivity and specificity of machine learning classifiers (MLCs for glaucoma diagnosis using Spectral Domain OCT (SD-OCT and standard automated perimetry (SAP. METHODS: Observational cross-sectional study. Sixty two glaucoma patients and 48 healthy individuals were included. All patients underwent a complete ophthalmologic examination, achromatic standard automated perimetry (SAP and retinal nerve fiber layer (RNFL imaging with SD-OCT (Cirrus HD-OCT; Carl Zeiss Meditec Inc., Dublin, California. Receiver operating characteristic (ROC curves were obtained for all SD-OCT parameters and global indices of SAP. Subsequently, the following MLCs were tested using parameters from the SD-OCT and SAP: Bagging (BAG, Naive-Bayes (NB, Multilayer Perceptron (MLP, Radial Basis Function (RBF, Random Forest (RAN, Ensemble Selection (ENS, Classification Tree (CTREE, Ada Boost M1(ADA,Support Vector Machine Linear (SVML and Support Vector Machine Gaussian (SVMG. Areas under the receiver operating characteristic curves (aROC obtained for isolated SAP and OCT parameters were compared with MLCs using OCT+SAP data. RESULTS: Combining OCT and SAP data, MLCs' aROCs varied from 0.777(CTREE to 0.946 (RAN.The best OCT+SAP aROC obtained with RAN (0.946 was significantly larger the best single OCT parameter (p<0.05, but was not significantly different from the aROC obtained with the best single SAP parameter (p=0.19. CONCLUSION: Machine learning classifiers trained on OCT and SAP data can successfully discriminate between healthy and glaucomatous eyes. The combination of OCT and SAP measurements improved the diagnostic accuracy compared with OCT data alone.

  8. Effect of the probiotic strain Bifidobacterium animalis subsp. lactis, BB-12®, on defecation frequency in healthy subjects with low defecation frequency and abdominal discomfort: a randomised, double-blind, placebo-controlled, parallel-group trial.

    Science.gov (United States)

    Eskesen, Dorte; Jespersen, Lillian; Michelsen, Birgit; Whorwell, Peter J; Müller-Lissner, Stefan; Morberg, Cathrine M

    2015-11-28

    The aim of the present study was to investigate the effect of Bifidobacterium animalis subsp. lactis, BB-12®, on two primary end points - defecation frequency and gastrointestinal (GI) well-being - in healthy adults with low defecation frequency and abdominal discomfort. A total of 1248 subjects were included in a randomised, double-blind, placebo-controlled trial. After a 2-week run-in period, subjects were randomised to 1 or 10 billion colony-forming units/d of the probiotic strain BB-12® or a matching placebo capsule once daily for 4 weeks. Subjects completed a diary on bowel habits, relief of abdominal discomfort and symptoms. GI well-being, defined as global relief of abdominal discomfort, did not show significant differences. The OR for having a defecation frequency above baseline for ≥50% of the time was 1·31 (95% CI 0·98, 1·75), P=0·071, for probiotic treatment overall. Tightening the criteria for being a responder to an increase of ≥1 d/week for ≥50 % of the time resulted in an OR of 1·55 (95% CI 1·22, 1·96), P=0·0003, for treatment overall. A treatment effect on average defecation frequency was found (P=0·0065), with the frequency being significantly higher compared with placebo at all weeks for probiotic treatment overall (all PEffects on defecation frequency were similar for the two doses tested, suggesting that a ceiling effect was reached with the one billion dose. Overall, 4 weeks' supplementation with the probiotic strain BB-12® resulted in a clinically relevant benefit on defecation frequency. The results suggest that consumption of BB-12® improves the GI health of individuals whose symptoms are not sufficiently severe to consult a doctor (ISRCTN18128385).

  9. Robust DTC Based on Adaptive Fuzzy Control of Double Star Synchronous Machine Drive with Fixed Switching Frequency

    Science.gov (United States)

    Boudana, Djamel; Nezli, Lazhari; Tlemçani, Abdelhalim; Mahmoudi, Mohand Oulhadj; Tadjine, Mohamed

    2012-05-01

    The double star synchronous machine (DSSM) is widely used for high power traction drives. It possesses several advantages over the conventional three phase machine. To reduce the torque ripple the DSSM are supplied with source voltage inverter (VSI). The model of the system DSSM-VSI is high order, multivariable and nonlinear. Further, big harmonic currents are generated. The aim of this paper is to develop a new direct torque adaptive fuzzy logic control in order to control DSSM and minimize the harmonics currents. Simulations results are given to show the effectiveness of our approach.

  10. A high-finesse Fabry–Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

    Energy Technology Data Exchange (ETDEWEB)

    Rakhman, A., E-mail: rahim@ornl.gov [Syracuse University, Department of Physics, Syracuse, NY 13244 (United States); Research Accelerator Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Hafez, M. [Old Dominion University, Applied Research Center, Norfolk, VA 23529 (United States); Nanda, S. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Benmokhtar, F. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); Duquesne University, Pittsburgh, PA 15282 (United States); Camsonne, A. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Cates, G.D. [University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Dalton, M.M. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Franklin, G.B. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); Friend, M. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Michaels, R.W. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Nelyubin, V. [University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Parno, D.S. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); University of Washington, Center for Experimental Nuclear Physics and Astrophysics and Department of Physics, Seattle, WA 98195 (United States); Paschke, K.D. [University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Quinn, B.P. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); and others

    2016-06-21

    A high-finesse Fabry–Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO{sub 3} crystal. The maximum achieved green power at 5 W infrared pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.06 GeV and 50 μA.

  11. A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

    CERN Document Server

    Rakhman, A; Nanda, S; Benmokhtar, F; Camsonne, A; Cates, G D; Dalton, M M; Franklin, G B; Friend, M; Michaels, R W; Nelyubin, V; Parno, D S; Paschke, K D; Quinn, B P; Souder, P A; Tobias, W A

    2016-01-01

    A high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532~nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064~nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO$_{3}$ crystal. The maximum achieved green power at 5 W IR pump power is 1.74 W with a total conversion efficiency of 34.8\\%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7~kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7\\%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0\\% precision in polarization measurements of an electron beam with energy and current of 1.0~GeV and 50~$\\mu$A.

  12. Broadly wavelength- and pulse width-tunable high-repetition rate light pulses from soliton self-frequency shifting photonic crystal fiber integrated with a frequency doubling crystal.

    Science.gov (United States)

    Lanin, Aleksandr A; Fedotov, Andrei B; Zheltikov, Aleksei M

    2012-09-01

    Soliton self-frequency shift (SSFS) in a photonic crystal fiber (PCF) pumped by a long-cavity mode-locked Cr:forsterite laser is integrated with second harmonic generation (SHG) in a nonlinear crystal to generate ultrashort light pulses tunable within the range of wavelengths from 680 to 1800 nm at a repetition rate of 20 MHz. The pulse width of the second harmonic output is tuned from 70 to 600 fs by varying the thickness of the nonlinear crystal, beam-focusing geometry, and the wavelength of the soliton PCF output. Wavelength-tunable pulses generated through a combination of SSFS and SHG are ideally suited for coherent Raman microspectroscopy at high repetition rates, as verified by experiments on synthetic diamond and polystyrene films.

  13. Double-porosity rock model and squirt flow in the laboratory frequency band%实验室频段的双孔岩石模型与喷射流

    Institute of Scientific and Technical Information of China (English)

    巴晶; 曹宏; 姚逢昌; 聂建新; 杨慧珠

    2008-01-01

    Biot theory research has been extended to the multi-scale heterogeneity in actual rocks. Focused on laboratory frequency bandwidth studies, we discuss the relationships between double-porosity and BISQ wave equations, analytically derive the degeneration method for double-porosity's return to BISQ, and give three necessary conditions which the degeneration must satisfy. By introducing dynamic permeability and tortuosity theory, a full set of dynamic double-porosity wave equations are derived. A narrow band approximation is made to simplify the numerical simulation for dynamic double-porosity wavefields. Finally, the pseudo-spectral method is used for wave simulation within the laboratory frequency band (50 kHz). Numerical results have proved the feasibility for dynamic double-porosity's description of squirt flow and the validity of the quasi-static approximation method.

  14. Coupling effect combined with incident polarization to modulate double split-ring-resonator in terahertz frequency range

    Science.gov (United States)

    Zhu, Mei; Lin, Yu-Sheng; Lee, Chengkuo

    2014-11-01

    This work examines the coupling effect in concentric double split-ring-resonator devices in terahertz (THz) range when the inner ring changes its relative orientation to the outer ring. Through detailed analysis on the simulation results of surface current and electrical field distributions, we look into the changes of inductance and capacitance in the system caused by structural layouts, and present a set of coherent theory that is solely rooted in the inductance-capacitance circuit analogy to systematically account for the resonance change. Such coupling effect combined with polarization of the incident wave is further explored to demonstrate continuous modulation of THz resonances. A variation range of transmission intensity from 20% to 80% has been successfully achieved. These experimental results demonstrate the promise of realizing future tunable THz filters by means of rotating sub-structures of the device only.

  15. A 200 mA CMOS low-dropout regulator with double frequency compensation techniques for SoC applications

    Institute of Scientific and Technical Information of China (English)

    Lei Qianqian; Chen Zhiming; Gong Zheng; Shi Yin

    2011-01-01

    This paper presents a 200 mA low-dropout (LDO) linear regulator using two modified techniques for frequency compensation.One technique is that the error amplifier uses a common source stage with variable load,which is controlled by the output current,is served as the second stage for a stable frequency response.The other technique is that the LDO uses a pole-zero tracking compensation technique at the error amplifier to achieve a good frequency response.The proposed circuit was fabricated and tested in HJTC 0.18 μm CMOS technology.The designed LDO linear regulator works under the input voltage of 2.8-5 V and provides up to 200 mA load current for an output voltage of 1.8 V.The total error of the output voltage due to line and load variation is less than 0.015%.The LDO die area is 630 × 550μm2 and the quiescent current is 130 μA.

  16. Effects of pyridoxine supplementation on severity, frequency and duration of migraine attacks in migraine patients with aura: A double-blind randomized clinical trial study in Iran.

    Directory of Open Access Journals (Sweden)

    Omid Sadeghi

    2015-06-01

    Full Text Available Migraine is a chronic disease that affects nearly 6% of men and 18% of women worldwide. There are various drugs, which can successfully decrease migraine symptoms and frequency of migraine attacks, but these drugs usually are expensive. Hence, this study aimed to assess the effects of pyridoxine supplementation on severity, frequency and duration of migraine attacks as well as headache diary results (HDR.This double-blind randomized clinical trial study was conducted on 66 patients with migraine with aura (MA in Khorshid and Emam Mosa Sadr clinics of Isfahan University of Medical Sciences, Iran, in 2013. Patients were randomly allocated to receive either pyridoxine supplements (80 mg pyridoxine per day or placebo. Severity, frequency and duration of migraine attacks and HDR were measured at baseline and at the end of the study.Mean age of patients was 34.24 ± 9.44 years old. Pyridoxine supplementation led to a significant decrease in headache severity (-2.20 ± 1.70 compared with -1 ± 1.50; P = 0.007, attacks duration (-8.30 ± 12.60 compared with -1.70 ± 9.60; P = 0.030 and HDR (-89.70 ± 134.60 compared with -6.10 ± 155.50; P = 0.040 compared with placebo, but was not effective on the frequency of migraine attacks (-2.30 ± 4 compared with -1.20 ± 7.80; P = 0.510.Pyridoxine supplementation in patients with MA was effective on headache severity, attacks duration and HDR, but did not affect the frequency of migraine attacks.

  17. Gain chip design, power scaling and intra-cavity frequency doubling with LBO of optically pumped red-emitting AlGaInP-VECSELs

    Science.gov (United States)

    Kahle, Hermann; Mateo, Cherry M. N.; Brauch, Uwe; Bek, Roman; Schwarzbäck, Thomas; Jetter, Michael; Graf, Thomas; Michler, Peter

    2016-03-01

    The wide range of applications in biophotonics, television or projectors, spectroscopy and lithography made the optically-pumped semiconductor (OPS) vertical external cavity surface-emitting lasers (VECSELs) an important category of power scalable lasers. The possibility of bandgap engineering, inserting frequency selective and converting elements into the open laser cavity and laser emission in the fundamental Gaussian mode leads to ongoing growth of the area of applications for tuneable laser sources. We present an AlGaInP-VECSEL system with a multi quantum well structure consisting of compressively strained GaInP quantum wells in an AlxGa1-xInP separate confinement heterostructure with an emission wavelength around 665 nm. The VECSEL chip with its n-λ cavity is pumped by a 532nm Nd:YAG laser under an angle to the normal incidence of 50°. In comparison, a gain chip design for high absorption values at pump wavelengths around 640nm with the use of quantum dot layers as active material is also presented. Frequency doubling is now realized with an antireflection coated lithium borate crystal, while a birefringent filter, placed inside the laser cavity under Brewster's angle, is used for frequency tuning. Further, power-scaling methods like in-well pumping as well as embedding the active region of a VECSEL between two transparent ic heaspreaders are under investigation.

  18. Highly sensitive liquid-level sensor based on dual-wavelength double-ring fiber laser assisted by beat frequency interrogation.

    Science.gov (United States)

    Dai, Yi; Sun, Qizhen; Tan, Sisi; Wo, Jianghai; Zhang, Jiejun; Liu, Deming

    2012-12-01

    A highly sensitive liquid-level sensor based on dual-wavelength single-longitudinal-mode fiber laser is proposed and demonstrated. The laser is formed by exploiting two parallel arranged phase-shift fiber Bragg gratings (ps-FBGs), acting as ultra-narrow bandwidth filters, into a double-ring resonators. By beating the dual-wavelength lasing output, a stable microwave signal with frequency stability better than 5 MHz is obtained. The generated beat frequency varies with the change of dual-wavelength spacing. Based on this characteristic, with one ps-FBG serving as the sensing element and the other one acting as the reference element, a highly sensitive liquid level sensor is realized by monitoring the beat frequency shift of the laser. The sensor head is directly bonded to a float which can transfer buoyancy into axial strain on the fiber without introducing other elastic elements. The experimental results show that an ultra-high liquid-level sensitivity of 2.12 × 10(7) MHz/m within the measurement range of 1.5 mm is achieved. The sensor presents multiple merits including ultra-high sensitivity, thermal insensitive, good reliability and stability.

  19. All-solid-state continuous-wave frequency-doubled Nd:YAG-BiBO laser with 2.8-W output power at 473 nm.

    Science.gov (United States)

    Czeranowsky, C; Heumann, E; Huber, G

    2003-03-15

    We report on a diode-pumped Nd:YAG laser with 4.6 W of linear polarized continuous-wave (cw) output power on the 4F3/2 --> 4I9/2 transitions at 946 nm. Three different crystals, cut for critical type I phase matching at room temperature, are used for the intracavity frequency doubling of the laser: 10-mm-long LiBaO5 (LBO), an 8-mm-long beta-BaB2O4 (BBO), and a 10.4-mm-long BiB3O6 (BiBO) grown by FEE GmbH. Up to 2.8 W of cw output power in the blue spectral range at 473 nm has been achieved with the BiBO crystal (2.1 W with BBO and 1.5 W with LBO).

  20. High power, picosecond green laser based on a frequency-doubled, all-fiber, narrow-bandwidth, linearly polarized, Yb-doped fiber laser

    Science.gov (United States)

    Tian, Wenyan; Isyanova, Yelena; Stegeman, Robert; Huang, Ye; Chieffo, Logan R.; Moulton, Peter F.

    2016-03-01

    We report on the development of an all-fiber, 68-kW-peak-power, 16-ps-pulse-width, narrow-bandwidth, linearly polarized, 1064-nm fiber laser suitable for high-power, picosecond-pulse-width, green-light generation. Our 1064-nm fiber laser delivered an average power of up to 110 W at a repetition of 100- MHz in a narrow bandwidth, with minimal nonlinear distortion. We developed a high-power, picosecond green source at 532 nm through use of single-pass frequency-doubling of our 1064-nm fiber laser in lithium triborate (LBO). Using a 15-mm long LBO crystal, we have generated 30 W of average power in the second harmonic with 73-W of fundamental average power, for a conversion efficiency of 41%.

  1. Determination of Matrine and Oxymatrine in Radix Sophorae Flavescentis by Resonance Rayleigh Scattering, Second-order Scattering and Frequency Doubling Scattering Technique

    Institute of Scientific and Technical Information of China (English)

    SONG Yan-qi; LIU Shao-pu; LIU Zhong-fang; HU Xiao-li

    2011-01-01

    In 0.1 mol/L HCl medium,12-tungstophosphoric(TP) acid reacted with matrine(Mat) and oxymatrine(Oxy)to form an ion-association complex.As a result,the new spectra of resonance Rayleigh scattering(RRS),second-order scattering(SOS) and frequency doubling scattering(FDS) appeared and their intensities were enhanced greatly.The maximum scattering wavelengths of RRS,SOS and FDS were located at 370,670 and 390 nm,respectively.The increments of scattering intensity were directly proportional to the concentration of Mat and Oxy in a certain range.Based on this,the method for the determination of matrine and oxymatrine has been established.It has been applied to the determination of matrine and oxymatrine in samples of Radix sophorae flavescentis with satisfactory result.The reaction mechanism and reasons of RRS enhancement were discussed.

  2. Electroabsorption modulators integrated with DFB lasers based on identical active double-stack MQW-layer structure with high-frequency performance

    Science.gov (United States)

    Stegmueller, Bernhard; Hanke, Christian

    2003-12-01

    Electro optic modulators are key components for fiber optic transmission at data rates exceeding 10Gbit/s. The monolithic integration of an electroabsorption (EA) modulator applying the quantum confined stark effect with a distributed feedback (DFB) laser diode was demonstrated using a novel approach based on a double-stack multiple quantum well (MQW) structure. This novel approach using an identical MQW layer structure for both devices, the DFB laser diode and the EA modulator, will be described and discussed. Recently, a maximum 3dB-cutoff frequency of 25 GHz was measured. Further experimental results obtained from devices operating at 1.3 μm and 1.55 μm, respectively, exhibit the potential of these devices for high-speed data rate transmission.

  3. Stable High Power and High Beam Quality Diode-Side-Pumped Continuous-Wave Intracavity Frequency-Doubled Nd:YAG Laser

    Institute of Scientific and Technical Information of China (English)

    CHENG Xian-Kun; ZHOU Yong; CUI Qian-Jin; YANG Feng; BO Yong; PENG Qin-Jun; CUI Da-Fu; XU Zu-Yan

    2009-01-01

    We report a stable high power and high beam quality diode-side-pumped cw green laser from intracavity frequency-doubled Nd:YAG laser with KTP.By using a L-shaped concave-convex resonator,designed with two Nd:YAG rods birefringence compensation,a large fundamental mode size in the laser crystal arid a tight focus in the nonlinear crystal could be obtained simultaneously.The green laser delivers a maximum 532nm output power of 23.2 W.Under 532 nm output power of 20.9 W,the beam quality factor is measured to be 4.1,and the fluctuation of the output power is less than 1.4% in an hour.

  4. Frequency-doubled DBR-tapered diode laser for direct pumping of Ti:sapphire lasers generating sub-20 fs pulses.

    Science.gov (United States)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika; Le, Tuan; Stingl, Andreas; Hasler, Karl-Heinz; Sumpf, Bernd; Erbert, Götz; Andersen, Peter E; Petersen, Paul Michael

    2011-06-20

    For the first time a single-pass frequency doubled DBR-tapered diode laser suitable for pumping Ti:sapphire lasers generating ultrashort pulses is demonstrated. The maximum output powers achieved when pumping the Ti:sapphire laser are 110 mW (CW) and 82 mW (mode-locked) respectively at 1.2 W of pump power. This corresponds to a reduction in optical conversion efficiencies to 75% of the values achieved with a commercial diode pumped solid-state laser. However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the Ti:sapphire laser when pumped with our diode laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20 fs can therefore be expected.

  5. 无刷双馈电动机最优压频控制策略%The Optimal Voltage Frequency Control Strategy of Brushless Double-fed Motor

    Institute of Scientific and Technical Information of China (English)

    邓先明; 王冬冬; 马志勋; 张贞飞

    2009-01-01

    无刷双馈电动机与其它电动机相比具有独特的优越性能,特别适合风机、水泵类负载的开环控制.文章以笼型无刷双馈电动机为研究对象,建立了无刷双馈电动机的数学模型,借助Matlab/Simulink仿真软件详细分析了电动机在调速过程中的最优压频控制策略.该策略可使电动机以最大功率因数和最小变频器容量稳定地运行在相应的转速上.%Compared with other motors, the brushless double-fed motor (BDFM) has its own unique advantages, especially suits for the open-loop control of loads of fans, pumps load and so on. Taking the cage brushless double-fed motor as research object, the paper established a mathematical model of the BDFM. Using Matlab/Simulink software, it analyzed the optimal voltage frequency control strategy in course of speed-regulation control in details. The strategy can make the motor run stablly in corresponding speed at the maximum power factor and the minimum converter capacity.

  6. Properties of pulse single-frequency laser and extra-cavity double frequency green laser%脉冲单频 Nd∶YVO4激光器及其倍频输出特性研究

    Institute of Scientific and Technical Information of China (English)

    董磊; 刘欣悦; 陈浩

    2015-01-01

    In order to manufacture a pulse single-frequency laser with master oscillator power amplifier( MO-PA) structure used for laser coherence imaging, the properties of acousto-optic Q-switched pulse single-fre-quency 1 064 nm laser used as MOPA laser seed, and properties of extra-cavity double frequency green laser were studied in the paer.1 064 nm pulse laser output with more than 20 ns pulse width was realized by means of acousto-optics Q-switch, and single-frequency running was realized by means of loop cavity and etalons with different thickness.The linewidth of 1 064 nm and 532 nm pulse lasers were studied.The experiment results show that there is almost complete coherence in all of the pulse width;1 064 nm pulse single-frequency laser with 28 nm pulse width and 6 .5 kW peak power and 532 nm laser with 20 ns pulse width and 0.5 kW peak power are obtained respectively.The efficiency of extra-cavity double-frequency is about 5.6%.The effect of laser pulse reduction by extra-cavity double-frequency is also validated by experiments.%为了研制激光干涉成像所需的主振荡功率放大( MOPA)结构脉冲单频激光器,本文完成MOPA激光器的种子源即声光调Q脉冲单频1064 nm激光器的特性研究,同时完成种子源腔外倍频绿光特性研究。脉冲单频激光器采用声光调Q模块实现脉宽约20 ns的1064 nm脉冲激光输出,采用环形腔设计并采用一组不同厚度的标准具实现单纵模运转。实验研究基频1064 nm和倍频532 nm激光脉冲的线宽,得出在全脉宽范围内都具有较高时间相干性的结论。实验分别获得脉宽约28 ns峰值功率约6.5 kW的1064 nm脉冲单频激光和脉宽约20 ns、峰值功率约0.5 kW的532 nm脉冲单频激光,腔外倍频效率为5.6%。实验同时也验证了腔外倍频的激光脉宽压缩效应。

  7. The double-resonance enhancement of stimulated low-frequency Raman scattering in silver-capped nanodiamonds

    Science.gov (United States)

    Baranov, A. N.; Butsen, A. V.; Ionin, A. A.; Ivanova, A. K.; Kuchmizhak, A. A.; Kudryashov, S. I.; Kudryavtseva, A. D.; Levchenko, A. O.; Rudenko, A. A.; Saraeva, I. N.; Strokov, M. A.; Tcherniega, N. V.; Zayarny, D. A.

    2017-09-01

    Hybrid plasmonic-dielectric nano- and (sub)microparticles exhibit magnetic and electrical dipolar Mie-resonances, which makes them useful as efficient basic elements in surface-enhanced spectroscopy, non-linear light conversion and nanoscale light control. We report the stimulated low-frequency Raman scattering (SLFRS) of a nanosecond ruby laser radiation (central wavelength λ = 694.3 nm (full-width at half-maximum ≈ 0.015 cm-1), gaussian 1/e-intensity pulsewidth τ ≈ 20 ns, TEM00-mode pulse energy Emax ≈ 0.3 J) in nanodiamond (R ≈ 120 nm) hydrosols, induced via optomechanical coherent excitation of fundamental breathing eigen-modes, and the two-fold enhancement of SLFRS in Ag-decorated nanodiamonds, characterized by hybrid dipolar resonances of electrical (silver) and magnetic (diamond) nature. Hybrid metal-dielectric particles were prepared by means of nanosecond IR-laser ablation of solid silver target in diamond hydrosols with consecutive Ag-capping of diamonds, and were characterized by scanning electron microscopy, UV-vis, photoluminescence and energy-dispersive X-ray spectroscopy. Intensities of the SLFR-scattered components and their size-dependent spectral shifts were measured in the highly sensitive stimulated scattering regime, indicating the high (≈ 30%) SLFRS conversion efficiency and the resonant character of the scattering species.

  8. Prospects of 4H-SiC Double Drift Region IMPATT Device as a Photo-Sensitive High-Power Source at 0.7 Terahertz Frequency Regime

    Directory of Open Access Journals (Sweden)

    Moumita Mukherjee

    2008-01-01

    Full Text Available The dynamic performance of wide-bandgap 4H-SiC based double drift region (p++ p n n++ IMPATT diode is simulated for the first time at terahertz frequency (0.7 Terahertz region. The simulation experiment establishes the potential of SiC based IMPATT diode as a high power (2.5×1011 Wm−2 terahertz source. The parasitic series resistance in the device is found to reduce the RF power output by 10.7%. The effects of external radiation on the simulated diode are also studied. It is found that (i the negative conductance and (ii the negative resistance of the diode decrease, while, the frequency of operation and the quality factor shift upward under photoillumination. Holes in 4H-SiC based IMPATT are found to dominate the modulation activities. The inequality in the magnitude of electron and hole ionization rates in the semiconductors may be correlated with these findings.

  9. Optimization of Vertical Double-Diffused Metal-Oxide Semiconductor (VDMOS) Power Transistor Structure for Use in High Frequencies and Medical Devices.

    Science.gov (United States)

    Farhadi, Rozita; Farhadi, Bita

    2014-01-01

    Power transistors, such as the vertical, double-diffused, metal-oxide semiconductor (VDMOS), are used extensively in the amplifier circuits of medical devices. The aim of this research was to construct a VDMOS power transistor with an optimized structure to enhance the operation of medical devices. First, boron was implanted in silicon by implanting unclamped inductive switching (UIS) and a Faraday shield. The Faraday shield was implanted in order to replace the gate-field parasitic capacitor on the entry part of the device. Also, implanting the UIS was used in order to decrease the effect of parasitic bipolar junction transistor (BJT) of the VDMOS power transistor. The research tool used in this study was Silvaco software. By decreasing the transistor entry resistance in the optimized VDMOS structure, power losses and noise at the entry of the transistor were decreased, and, by increasing the breakdown voltage, the lifetime of the VDMOS transistor lifetime was increased, which resulted in increasing drain flow and decreasing Ron. This consequently resulted in enhancing the operation of high-frequency medical devices that use transistors, such as Radio Frequency (RF) and electrocardiograph machines.

  10. Comparison of size modulation and conventional standard automated perimetry with the 24-2 test protocol in glaucoma patients

    Science.gov (United States)

    Hirasawa, Kazunori; Shoji, Nobuyuki; Kasahara, Masayuki; Matsumura, Kazuhiro; Shimizu, Kimiya

    2016-05-01

    This prospective randomized study compared test results of size modulation standard automated perimetry (SM-SAP) performed with the Octopus 600 and conventional SAP (C-SAP) performed with the Humphrey Field Analyzer (HFA) in glaucoma patients. Eighty-eight eyes of 88 glaucoma patients underwent SM-SAP and C-SAP tests with the Octopus 600 24-2 Dynamic and HFA 24-2 SITA-Standard, respectively. Fovea threshold, mean defect, and square loss variance of SM-SAP were significantly correlated with the corresponding C-SAP indices (P < 0.001). The false-positive rate was slightly lower, and false-negative rate slightly higher, with SM-SAP than C-SAP (P = 0.002). Point-wise threshold values obtained with SM-SAP were moderately to strongly correlated with those obtained with C-SAP (P < 0.001). The correlation coefficients of the central zone were significantly lower than those of the middle to peripheral zone (P = 0.031). The size and depth of the visual field (VF) defect were smaller (P = 0.039) and greater (P = 0.043), respectively, on SM-SAP than on C-SAP. Although small differences were observed in VF sensitivity in the central zone, the defect size and depth and the reliability indices between SM-SAP and C-SAP, global indices of the two testing modalities were well correlated.

  11. Relationship between Spectral-Domain Optical Coherence Tomography and Standard Automated Perimetry in Healthy and Glaucoma Patients

    Directory of Open Access Journals (Sweden)

    Beatriz Abadia

    2014-01-01

    Full Text Available Objective. To evaluate the relationship between spectral-domain optical coherence tomography (OCT and standard automated perimetry (SAP in healthy and glaucoma individuals. Methods. The sample comprised 338 individuals divided into 2 groups according to intraocular pressure and visual field outcomes. All participants underwent a reliable SAP and imaging of the optic nerve head with the Cirrus OCT. Pearson correlations were calculated between threshold sensitivity values of SAP (converted to linear scale and OCT parameters. Results. Mean age did not differ between the control and glaucoma groups (59.55 ± 9.7 years and 61.05 ± 9.4 years, resp.; P=0.15. Significant differences were found for the threshold sensitivities at each of the 52 points evaluated with SAP (P<0.001 and the peripapillary retinal nerve fiber layer (RNFL thicknesses, except at 3 and 9 clock-hour positions between both groups. Mild to moderate correlations (ranging between 0.286 and 0.593; P<0.001 were observed between SAP and most OCT parameters in the glaucoma group. The strongest correlations were found between the inferior RNFL thickness and the superior hemifield points. The healthy group showed lower and weaker correlations than the glaucoma group. Conclusions. Peripapillary RNFL thickness measured with Cirrus OCT showed mild to moderate correlations with SAP in glaucoma patients.

  12. Integration and fusion of standard automated perimetry and optical coherence tomography data for improved automated glaucoma diagnostics

    Directory of Open Access Journals (Sweden)

    Bizios Dimitrios

    2011-08-01

    Full Text Available Abstract Background The performance of glaucoma diagnostic systems could be conceivably improved by the integration of functional and structural test measurements that provide relevant and complementary information for reaching a diagnosis. The purpose of this study was to investigate the performance of data fusion methods and techniques for simple combination of Standard Automated Perimetry (SAP and Optical Coherence Tomography (OCT data for the diagnosis of glaucoma using Artificial Neural Networks (ANNs. Methods Humphrey 24-2 SITA standard SAP and StratusOCT tests were prospectively collected from a randomly selected population of 125 healthy persons and 135 patients with glaucomatous optic nerve heads and used as input for the ANNs. We tested commercially available standard parameters as well as novel ones (fused OCT and SAP data that exploit the spatial relationship between visual field areas and sectors of the OCT peripapillary scan circle. We evaluated the performance of these SAP and OCT derived parameters both separately and in combination. Results The diagnostic accuracy from a combination of fused SAP and OCT data (95.39% was higher than that of the best conventional parameters of either instrument, i.e. SAP Glaucoma Hemifield Test (p Conclusions Compared to the use of SAP parameters, input from the combination of fused OCT and SAP parameters, and from fused OCT data, significantly increased the performance of ANNs. Integrating parameters by including a priori relevant information through data fusion may improve ANN classification accuracy compared to currently available methods.

  13. High-Power Red Light Generation by Intra-Cavity Frequency-Doubling of a Side-Pumped Nd:YAG Laser in a LiB.3O5 Crystal

    Institute of Scientific and Technical Information of China (English)

    SUN Zhi-Pei; ZHANG Hong-Bo; CUI Da-Fu; XU Zu-Yan; LI Rui-Ning; BI Yong; YANG Xiao-Dong; BO Yong; HOU Wei; ZHANG Ying; WANG Gui-Ling; ZHAO Wu-Li

    2004-01-01

    We report the generation of high-power red light radiation of 11.2 W in a LiB3O5(LBO) crystal with intra-cavity frequency doubling of two compact and simple side-pumped Nd:YAG laser modules under a repetition rate of 3.5kHz. The pulse width of output is about 180 ± 20ns. The beam quality of the M2 value is 15 ± 3 in both the directions. This excellent laser performance demonstrates that the Nd:YAG laser with LBO intracavity frequency doubling is an promising method for generating red light with high brightness.

  14. Frequency Scale Factors for Some Double-Hybrid Density Functional Theory Procedures: Accurate Thermochemical Components for High-Level Composite Protocols.

    Science.gov (United States)

    Chan, Bun; Radom, Leo

    2016-08-09

    In the present study, we have obtained geometries and frequency scale factors for a number of double-hybrid density functional theory (DH-DFT) procedures. We have evaluated their performance for obtaining thermochemical quantities [zero-point vibrational energies (ZPVE) and thermal corrections for 298 K enthalpies (ΔH298) and 298 K entropies (S298)] to be used within high-level composite protocols (using the W2X procedure as a probe). We find that, in comparison with the previously prescribed protocol for optimization and frequency calculations (B3-LYP/cc-pVTZ+d), the use of contemporary DH-DFT methods such as DuT-D3 and DSD-type procedures leads to a slight overall improved performance compared with B3-LYP. A major strength of this approach, however, lies in the better robustness of the DH-DFT methods in that the largest deviations are notably smaller than those for B3-LYP. In general, the specific choices of the DH-DFT procedure and the associated basis set do not drastically change the performance. Nonetheless, we find that the DSD-PBE-P86/aug'-cc-pVTZ+d combination has a very slight edge over the others that we have examined, and we recommend its general use for geometry optimization and vibrational frequency calculations, in particular within high-level composite methods such as the higher-level members of the WnX series of protocols. The scale factors determined for DSD-PBE-P86/aug'-cc-pVTZ+d are 0.9830 (ZPVE), 0.9876 (ΔH298), and 0.9923 (S298).

  15. Double screen frequency selective surface structure optimized by genetic algorithm%双屏频率选择表面结构的遗传算法优化

    Institute of Scientific and Technical Information of China (English)

    汪剑波; 卢俊

    2011-01-01

    双屏频率选择表面能够更好地实现平顶效应和快速下降的边缘,是一种实现雷达舱对探测带外雷达波隐身的有效手段.本文针对双屏频率选择表面(FSS)在电磁波不同角度入射下的宽带通应用,采用遗传算法对FSS介质厚度、介电常数、单元图形、排列周期进行了整体优化,给出优化后的FSS结构和传输特性曲线;同时采用镀膜和光刻技术制备出相应的实验件,在微波暗室进行了测试.结果表明,优化后的结构在保证2 GHz的工作带宽下,对电磁波的入射角度有良好的传输稳定性,这为实现双屏FSS在曲面大角度下的应用奠定了基础.%Double screen frequency selective surface(FSS) is a very effective means of realizing the invisibility of radar-cabin from the detection of radar wave since it can well realize the flattened effect and rapid decrease. In this paper, the thickness, the dielectric constant, the element graph and the arrangement periodicity of an FSS medium are investigated by Genetic Algorithm (GA) when electromagnetic waves are incident on the double screen FSS at varying angles, and an optimized FSS structure and transmission characteristics are obtained. Meanwhile, the relevant experimental samples are prepared by means of coating and lithography and are tested in microwave anechoic chamber. The results show that the optimized structure has a better stability with respect to incident angle of electromagnetic wave under the condition of 2GHz operation, thereby laying the foundation for the application of double screen FSS to curved surfaces at wide angles.

  16. Output Mode Simulation of Frequency Doubling External Resonant in PPLN%PPLN谐振倍频外腔输出模场的模拟研究

    Institute of Scientific and Technical Information of China (English)

    卢峰; 张蓉竹; 刘正颍; 孙年春

    2011-01-01

    To study the output mode distribution of the frequency doubling resonant in PPLN,the field distributions and beam quality M2 factor of the plano-concave resonator or dual-cavity were calculated and compared.The output fundamental modes of them with tilted Gaussian-reflectivity mirrors were simulated with Fourier transformation method and Fox-Li iterative method.The results show that the output fundamental mode of the frequency doubling external resonants is Gaussian distribution,and cavity length changes have less effect on the output beam quality.The output beam quality of the plano-concave resonator is M2=1.296,divergence angle θ=58.084μrad,and the Dual-cavity is M2=6.930,θ= 310.56μrad.The output beam quality of the plano-concave resonator is superior to the Dual-cavity.%为了探究PPLN外部谐振倍频腔的输出模式,从菲涅尔-基尔霍夫衍射积分公式出发,采用快速傅里叶变换法(FFT)和Fox-Li迭代法数值模拟高斯反射率圆形平凹倍频腔输出基模的场强分布、相位分布和光束质量M2因子,同时与圆形双凹倍频腔做了比较.计算结果表明,两类倍频谐振腔输出塞模均为高斯分布,腔长变化对两类倍频腔输出光束质量的影响较小.平凹倍频腔输出光束质量M2=1.296,远场发散角θ=58.084 μrad;而双凹倍频腔输出光束质量M2=6.930,θ=310.56 μrad.平凹倍频腔输出光束质量明显优于双凹倍频腔.

  17. Heating test on three-phase asynchronous motors by double-frequency or equivalent loading methods; Ensayo de calentamiento sobre motores asincronicos trifasicos por el metodo de la doble frecuencia o de la carga fantasma

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, Edgardo J.; Massa, Pablo A.; Urtiaga, Ricardo [La Plata Univ. Nacional (Argentina). Facultad de Ingenieria. Dept. de Electrotecnia

    1997-12-31

    This work comments the wiring temperature tests in three-phase high power asynchronous motors. It analyses an alternative method called double frequency or equivalent loading method which should be able to present similar effects of the direct method. A comparison between both methods is presented 4 refs., 5 figs., 1 tab.; e-mail: massa at isis.unlp.edu.ar

  18. Nonequilibrium Green's function theory of resonant steady state photoconduction in a double quantum well FET subject to THz radiation at plasmon frequency

    Science.gov (United States)

    Morgenstern Horing, Norman J.; Popov, Vyacheslav V.

    2006-04-01

    Recent experimental observations by X.G. Peralta and S.J. Allen, et al. of dc photoconductivity resonances in steady source-drain current subject to terahertz radiation in a grid-gated double-quantum well FET suggested an association with plasmon resonances. This association was definitively confirmed for some parameter ranges in our detailed electrodynamic absorbance calculations. In this paper we propose that the reason that the dc photoconductance resonances match the plasmon resonances in semiconductors is based on a nonlinear dynamic screening mechanism. In this, we employ a shielded potential approximation that is nonlinear in the terahertz field to determine the nonequilibrium Green's function and associated density perturbation that govern the nonequilibrium dielectric polarization of the medium. This ''conditioning'' of the system by the incident THz radiation results in resonant polarization response at the plasmon frequencies which, in turn, causes a sharp drop of the resistive shielded impurity scattering potentials and attendant increase of the dc source-drain current. This amounts to disabling the impurity scattering mechanism by plasmon resonant behavior in nonlinear screening.

  19. A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd:YAG laser

    Institute of Scientific and Technical Information of China (English)

    Wang Yu-Ye; Xu De-Gang; Liu Chang-Ming; Wang Wei-Peng; Yao Jian-Quan

    2012-01-01

    We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal.By using a composite ceramic Nd:YAG rod and a type-Ⅱ high gray track resistance KTP (HGTR-KTP) crystal,a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz,with a diode-to-green optical conversion of 14.68%,and a pulse width of 162 ns.To the best of our knowledge,both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date.The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.

  20. Study on the interaction between albendazole and eosin Y by fluorescence, resonance Rayleigh scattering and frequency doubling scattering spectra and their analytical applications

    Science.gov (United States)

    Tian, Fengling; Huang, Wei; Yang, Jidong; Li, Qin

    In pH 3.25-3.35 Britton-Robinson (BR) buffer solution, albendazole (ABZ) could react with eosin Y (EY) to form a 1:1 ion-association complex, which not only results in the quenching of fluorescence, but also resulted in the great enhancement of resonance Rayleigh scattering (RRS) and frequency doubling scattering (FDS). Furthermore, a new RRS spectrum will appear, and the maximum RRS wavelength was located at about 356 nm. The detection limit for ABZ were 21.51 ng mL-1 for the fluorophotometry, 6.93 ng mL-1 for the RRS method and 12.89 ng mL-1 for the FDS method. Among them, the RRS method had the highest sensitivity. The experimental conditions were optimized and effects of coexisting substances were evaluated. Meanwhile, the influences of coexisting substances were tested. The methods have been successfully applied to the determination of ABZ in capsules and human urine samples. The composition and structure of the ion-association complex and the reaction mechanism were discussed.

  1. Increased frequency of asynapsis and associated meiotic silencing of heterologous chromatin in the presence of irradiation-induced extra DNA double strand breaks.

    Science.gov (United States)

    Schoenmakers, Sam; Wassenaar, Evelyne; van Cappellen, Wiggert A; Derijck, Alwin A; de Boer, Peter; Laven, Joop S E; Grootegoed, J Anton; Baarends, Willy M

    2008-05-01

    In meiotic prophase of male placental mammals, the heterologous X and Y chromosomes remain largely unsynapsed, which activates meiotic sex chromosome inactivation (MSCI), leading to formation of the transcriptionally silenced XY body. MSCI is most likely related to meiotic silencing of unsynapsed chromatin (MSUC), a mechanism that can silence autosomal unsynapsed chromatin. However, heterologous synapsis and escape from silencing also occur. In mammalian species, formation of DNA double strand breaks (DSBs) during leptotene precedes meiotic chromosome pairing. These DSBs are essential to achieve full synapsis of homologous chromosomes. We generated 25% extra meiotic DSBs by whole body irradiation of mice. This leads to a significant increase in meiotic recombination frequency. In mice carrying translocation chromosomes with synaptic problems, we observed an approximately 35% increase in asynapsis and MSUC of the nonhomologous region in the smallest chromosome pair following irradiation. However, the same nonhomologous region in the largest chromosome pair, shows complete synapsis and escape from MSUC in almost 100% of the nuclei, irrespective of exposure to irradiation. We propose that prevention of synapsis and associated activation of MSUC is linked to the presence of unrepaired meiotic DSBs in the nonhomologous region. Also, spreading of synaptonemal complex formation from regions of homology may act as an opposing force, and drive heterologous synapsis.

  2. Design and Analysis of Double-Gate MOSFETs for Ultra-Low Power Radio Frequency Identification (RFID: Device and Circuit Co-Design

    Directory of Open Access Journals (Sweden)

    Tony T. Kim

    2011-07-01

    Full Text Available Recently, double-gate MOSFETs (DGMOSFETs have been shown to be more optimal for ultra-low power circuit design due to the improved subthreshold slope and the reduced leakage current compared to bulk CMOS. However, DGMOSFETs for subthreshold circuit design have not been much explored in comparison to those for strong inversion-based design. In this paper, various configurations of DGMOSFETs, such as tied/independent gates and symmetric/asymmetric gate oxide thickness are explored for ultra-low power and high efficient radio frequency identification (RFID design. Comparison of bulk CMOS with DGMOSFETs has been conducted in ultra-low power subthreshold digital logic design and rectifier design, emphasizing the scope of the nano-scale DGMOSFET technology for future ultra-low power systems. The DGMOSFET-based subthreshold logic improves energy efficiency by more than 40% compared to the bulk CMOS-based logic at 32 nm. Among the various DGMOSFET configurations for RFID rectifiers, symmetric tied-gate DGMOSFET has the best power conversion efficiency and the lowest power consumption.

  3. Effect of double AlN buffer layer on the qualities of GaN films grown by radio-frequency molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Li Xin-Hua; Zhong Fei; Qiu Kai; Yin Zhi-Jun; Ji Chang-Jian

    2008-01-01

    This paper reports that the GaN thin films with Ga-polarity and high quality were grown by radio-frequency molecular beam epitaxy on sapphire (0001) substrate with a double A1N buffer layer. The buffer layer consists of a high-temperature (HT) AlN layer and a low-temperature (LT) AlN layer grown at 800℃ and 600℃, respectively. It is demonstrated that the HT-AlN layer can result in the growth of GaN epilayer in Ga-polarity and the LT-AlN layer is helpful for the improvement of the epilayer quality. It is observed that the carrier mobility of the GaN epilayer increases from 458 to 858cm2/V.s at room temperature when the thickness of LT-AlN layer varies from 0 to 20nm. The full width at half maximum of x-ray rocking curves also demonstrates a substantial improvement in the quality of GaN epilayers by the utilization of LT-AlN layer.

  4. High-speed singulation of electronic packages using a frequency-doubled Nd:YAG laser in a water jet and realization of a 200-W green laser

    Science.gov (United States)

    Wagner, Frank R.; Hu, Wentao; Spiegel, Akos; Vago, Nandor; Richerzhagen, Bernold

    2003-07-01

    Each electronic chip is packaged in order to connect the integrated circuit and the printed circuit board. In consequence high-speed singulation of packages is an important step in the manufacturing process of electronic devices. The widely used technique of abrasive sawing encounters problems due to the combination of different materials used in packages such as copper and mold compound. The sawing blade rapidly blunts because of the copper adhering to the saw blade and covering the diamonds. In fact, the abrasive saw, well adapted to silicon wafer sawing, has problems to adapt to package materials. It has already been shown that the water jet guided laser can be used for efficient high quality singulation of leadframe based packages. In this technique a low-pressure water jet guides the laser beam like an optical fiber, providing efficient cooling of the cutting kerf at exactly the point that was heated during the laser pulse. We present new cutting results using a frequency doubled Nd:YAG laser with 100 W average power, and the combination setup for generating a 200 W green laser beam. The timing between the two lasers can be precisely controlled.

  5. High-Power Continuous-Wave Diode-End-Pumped Intracavity Frequency Doubled Nd:YVO4 Laser at 671 nm with a Compact Three-Element Cavity

    Institute of Scientific and Technical Information of China (English)

    ZHOU Rui; DING Xin; WEN Wu-Qi; CAI Zhi-Qiang; WANG Peng; YAO Jian-Quan

    2006-01-01

    @@ We report a high-power high-effcient continuous-wave (cw) diode-end-pumped Nd:YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope efficiency of 37.3%. By inserting a type-I critical phase-matched LBO crystal as intracavity frequencydoubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diodepumped solid-state Nd:YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.

  6. Determination of thorium (IV) using isophthalaldehyde-tetrapyrrole as probe by resonance light scattering, second-order scattering and frequency-doubling scattering spectra.

    Science.gov (United States)

    Wang, Jiao; Xue, Jinhua; Xiao, Xilin; Xu, Li; Jiang, Min; Peng, Pengcheng; Liao, Lifu

    2017-12-05

    The coordination reaction of thorium (IV) with a ditopic bidentate ligand to form supramolecular polymer was studied by resonance light scattering (RLS) spectra, second-order scattering (SOS) spectra and frequency-doubling scattering (FDS) spectra, respectively. The ditopic bidentate ligand is isophthalaldehyde-tetrapyrrole (IPTP). It was synthesized through a condensation reaction of isophthalaldehyde with pyrrole. The formation of supramolecular polymer results in remarkable intensity enhancements of the three light scattering signals. The maximum scattering wavelengths of RLS, FDS and SOS were 290, 568 and 340nm, respectively. The reaction was used to establish new light scattering methods for the determination of thorium (IV) by using IPTP as probe. Under optimum conditions, the intensity enhancements of RLS, SOS and FDS were directly proportional to the concentration of thorium (IV) in the ranges of 0.01 to 1.2μgmL(-1), 0.05 to 1.2μgmL(-1) and 0.05 to 1.2μgmL(-1), respectively. The detection limits were 0.003μgmL(-1), 0.012μgmL(-1) and 0.021μgmL(-1), respectively. The methods were suitable for analyzing thorium (IV) in actual samples. The results show acceptable recoveries and precision compared with a reference method. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. DNA fusion-gene vaccination in patients with prostate cancer induces high-frequency CD8(+) T-cell responses and increases PSA doubling time.

    Science.gov (United States)

    Chudley, Lindsey; McCann, Katy; Mander, Ann; Tjelle, Torunn; Campos-Perez, Juan; Godeseth, Rosemary; Creak, Antonia; Dobbyn, James; Johnson, Bernadette; Bass, Paul; Heath, Catherine; Kerr, Paul; Mathiesen, Iacob; Dearnaley, David; Stevenson, Freda; Ottensmeier, Christian

    2012-11-01

    We report on the immunogenicity and clinical effects in a phase I/II dose escalation trial of a DNA fusion vaccine in patients with prostate cancer. The vaccine encodes a domain (DOM) from fragment C of tetanus toxin linked to an HLA-A2-binding epitope from prostate-specific membrane antigen (PSMA), PSMA(27-35). We evaluated the effect of intramuscular vaccination without or with electroporation (EP) on vaccine potency. Thirty-two HLA-A2(+) patients were vaccinated and monitored for immune and clinical responses for a follow-up period of 72 weeks. At week 24, cross-over to the immunologically more effective delivery modality was permitted; this was shown to be with EP based on early antibody data, and subsequently, 13/15 patients crossed to the +EP arm. Thirty-two HLA-A2(-) control patients were assessed for time to next treatment and overall survival. Vaccination was safe and well tolerated. The vaccine induced DOM-specific CD4(+) and PSMA(27)-specific CD8(+) T cells, which were detectable at significant levels above baseline at the end of the study (p = 0.0223 and p = 0.00248, respectively). Of 30 patients, 29 had a measurable CD4(+) T-cell response and PSMA(27)-specific CD8(+) T cells were detected in 16/30 patients, with or without EP. At week 24, before cross-over, both delivery methods led to increased CD4(+) and CD8(+) vaccine-specific T cells with a trend to a greater effect with EP. PSA doubling time increased significantly from 11.97 months pre-treatment to 16.82 months over the 72-week follow-up (p = 0.0417), with no clear differential effect of EP. The high frequency of immunological responses to DOM-PSMA(27) vaccination and the clinical effects are sufficiently promising to warrant further, randomized testing.

  8. Generation of high-energy sub-20 fs pulses tunable in the 250-310 nm region by frequency doubling of a high-power noncollinear optical parametric amplifier.

    Science.gov (United States)

    Beutler, Marcus; Ghotbi, Masood; Noack, Frank; Brida, Daniele; Manzoni, Cristian; Cerullo, Giulio

    2009-03-15

    We report on the generation of powerful sub-20 fs deep UV pulses with 10 microJ level energy and broadly tunable in the 250-310 nm range. These pulses are produced by frequency doubling a high-power noncollinear optical parametric amplifier and compressed by a pair of MgF2 prisms to an almost transform-limited duration. Our results provide a power scaling by an order of magnitude with respect to previous works.

  9. Quasi-flat-top frequency-doubled Nd:glass laser for pumping of high-power Ti:sapphire amplifiers at a 0.1 Hz repetition rate.

    Science.gov (United States)

    Yanovsky, Victor; Kalinchenko, Galina; Rousseau, Pascal; Chvykov, Vladimir; Mourou, Gerard; Krushelnick, Karl

    2008-04-20

    A Nd:glass laser based on a novel design delivers up to 120 J energy pulses with a quasi-flat-top spatial profile at a 0.1 Hz repetition rate. The laser output is frequency-doubled with 50% efficiency and used to pump Ti:sapphire amplifiers. The developed design is perspective for use in the currently contemplated next step in ultra-high-intensity laser development.

  10. [Electronystagmographic objective perimetry].

    Science.gov (United States)

    Makabe, R

    1990-01-01

    We have recently been referred patients with visual field contraction from simulation or aggravation. For unmasking, we used optokinetic nystagmus, which can also be induced by stimulation of the peripheral retina. At electronystagmography the central portion of the screen was covered from 20 degrees-60 degrees by means of a black disk in front of the projection nystagmus drum. In the centre of the screen a light spot was installed, which blocked the nystagmus. On turning off the light spot, the optokinetic nystagmus was registered when there was no visual contraction at this degree. The examination was successful except for one case with coarse, spontaneous nystagmus in all 18 eyes of 10 patients, in which a visual field contraction from simulation or aggravation was suspected.

  11. Sensibilidade do estímulo de tamanho I na perimetria computadorizada acromática para a detecção de defeitos glaucomatosos no campo visual: análise comparativa com as perimetrias de ondas curtas e acromática convencional (SITA Sensitivity of size I stimulus in achromatic automated perimetry for detection of glaucomatous visual field defects: a comparative analysis with short wavelength automated perimetry and standard automated perimetry (SITA

    Directory of Open Access Journals (Sweden)

    Tessa de Cerqueira Lemos Mattos

    2008-04-01

    Full Text Available OBJETIVO: Comparar a sensibilidade e especificidade da perimetria acromática com estímulo de tamanho I (BB-I com a perimetria acromática convencional (estratégia SITA e a perimetria azul-amarelo (SWAP para o diagnóstico precoce do glaucoma. MÉTODOS: Setenta e três olhos de 73 pacientes suspeitos, glaucomatosos e normais foram submetidos às perimetrias SITA 24-2, BB-I e SWAP. Após aplicação de critérios específicos de anormalidade para interpretação dos resultados, calculou-se a sensibilidade, a especificidade e a área sob a curva ROC (Receiver Operating Characteristic para cada um dos exames. As áreas sob as curvas ROC foram comparadas aos pares com o teste Z univariável e significância 5%. RESULTADOS: O BB-I demonstrou maior sensibilidade (100% e menor especificidade (75,7%. O SWAP revelou menor sensibilidade (69,4%, porém maior especificidade (89,2%. A comparação pareada entre as curvas ROC não revelou diferença estatisticamente significante entre as três técnicas perimétricas estudadas. CONCLUSÕES: O BB-I revelou-se eficaz na detecção de defeitos precoces de campo visual no glaucoma. Esta técnica soma-se ao armamentário semiológico disponível para o diagnóstico funcional precoce da neuropatia óptica glaucomatosa.PURPOSE: To compare sensitivity and specificity of achromatic perimetry with size I stimulus (WW-I with standard automated perimetry (SITA strategy and blue on yellow perimetry (SWAP for early diagnosis of glaucoma. METHODS: Seventy-three eyes of 73 suspects, glaucomatous and normal subjects underwent automated perimetry with SITA 24-2, WW-I and SWAP. After application of specific criteria of abnormality, sensitivity, specificity, and the area under ROC (Receiver Operating Characteristic curve were calculated for each of the examinations. The areas under the ROC curve were compared pair-wisely with the univariable Z test and significance set at 5%. RESULTS: WW-I displayed the greatest sensitivity

  12. The role of hemifield sector analysis in multifocal visual evoked potential objective perimetry in the early detection of glaucomatous visual field defects

    Directory of Open Access Journals (Sweden)

    Mousa MF

    2013-05-01

    Full Text Available Mohammad F Mousa,1 Robert P Cubbidge,2 Fatima Al-Mansouri,1 Abdulbari Bener3,41Department of Ophthalmology, Hamad Medical Corporation, Doha, Qatar; 2School of Life and Health Sciences, Aston University, Birmingham, UK; 3Department of Medical Statistics and Epidemiology, Hamad Medical Corporation, Department of Public Health, Weill Cornell Medical College, Doha, Qatar; 4Department Evidence for Population Health Unit, School of Epidemiology and Health Sciences, University of Manchester, Manchester, UKObjective: The purpose of this study was to examine the effectiveness of a new analysis method of mfVEP objective perimetry in the early detection of glaucomatous visual field defects compared to the gold standard technique.Methods and patients: Three groups were tested in this study; normal controls (38 eyes, glaucoma patients (36 eyes, and glaucoma suspect patients (38 eyes. All subjects underwent two standard 24-2 visual field tests: one with the Humphrey Field Analyzer and a single mfVEP test in one session. Analysis of the mfVEP results was carried out using the new analysis ­protocol: the hemifield sector analysis protocol.Results: Analysis of the mfVEP showed that the signal to noise ratio (SNR difference between superior and inferior hemifields was statistically significant between the three groups (analysis of variance, P < 0.001 with a 95% confidence interval, 2.82, 2.89 for normal group; 2.25, 2.29 for glaucoma suspect group; 1.67, 1.73 for glaucoma group. The difference between superior and inferior hemifield sectors and hemi-rings was statistically significant in 11/11 pair of sectors and hemi-rings in the glaucoma patients group (t-test P < 0.001, statistically significant in 5/11 pairs of sectors and hemi-rings in the glaucoma suspect group (t-test P < 0.01, and only 1/11 pair was statistically significant (t-test P < 0.9. The sensitivity and specificity of the hemifield sector analysis protocol in detecting glaucoma was 97% and 86

  13. Low-frequency and tuning characteristic of band gap in a symmetrical double-sided locally resonant phononic crystal plate with slit structure

    Science.gov (United States)

    Wang, X. P.; Jiang, P.; Song, A. L.

    2016-09-01

    In this paper, the low-frequency and tuning characteristic of band gap in a two-dimensional phononic crystal structure, consisting of a square array of aluminum cylindrical stubs deposited on both sides of a thin rubber plate with slit structure, are investigated. Using the finite element method, the dispersion relationships and power transmission spectra of this structure are calculated. In contrast to a typical phononic crystal without slit structure, the proposed slit structure shows band gaps at lower frequencies. The vibration modes of the band gap edges are analyzed to clarify the mechanism of the lowest band gaps. Additionally, the influence of the slit parameters and stub parameters on the band gaps in slit structure are investigated. The geometrical parameters of the slits and stubs were found to influence the band gaps; this is critical to understand for practical applications. These results will help in fabricating phononic crystal structures whose band frequency can be modulated at lower frequencies.

  14. Perimetria computadorizada e manual em pacientes com defeitos perimétricos temporais avançados causados por tumores supra-selares Computerized and manual perimetry in patientes with severe temporal visual field defects due to supraselar tumors

    Directory of Open Access Journals (Sweden)

    Andrea Pereira

    2005-10-01

    Full Text Available OBJETIVO: Estudar, ao perímetro de Goldmann, um grupo de pacientes com hemianopsia completa ao perímetro Humphrey (24-2 full threshold test, e verificar em quantos casos a perimetria computadorizada deixou de identificar a presença de campo visual periférico residual. MÉTODOS: Dezenove pacientes com defeitos campimétricos por compressão quiasmática foram estudados prospectivamente por meio das perimetrias manual e computadorizada. Vinte e cinco olhos com hemianopsia temporal completa pelo programa 24-2 do Humphrey Field Analyzer foram selecionados e estudados pela perimetria manual de Goldmann para avaliar a presença de campo visual periférico residual. De acordo com os resultados ao perímetro de Goldmann, os olhos foram divididos em 2 grupos: grupo 1, os portadores de hemianopsia temporal completa ao Goldmann e grupo 2, os portadores de campo visual temporal periférico residual. Foi calculada a média do "mean deviation" fornecido pelo aparelho nos dois grupos e o resultado foi comparado pelo teste t de Student. RESULTADOS: A perimetria computadorizada deixou de identificar a presença de campo visual periférico residual em 17 dos 25 olhos (68%. Os valores médios do "mean deviation" no grupo 1 e grupo 2 foram respectivamente -15,43 e -15,93. O estudo estatístico não mostrou diferença significativa entre os dois valores. CONCLUSÕES: A perimetria computadorizada Humphrey com o programa 24-2 threshold test deixa de identificar remanescentes temporais de campo visual em grande porcentagem de pacientes com compressão quiasmática grave. A análise do "mean deviation" fornecido pelo aparelho não permite identificar estes casos. Pacientes estudados ao perímetro automático e apresentando hemianopsia temporal completa, devem complementar sua avaliação perimétrica com a pesquisa por áreas remanescentes no campo visual temporal.PURPOSE: To study, on Goldmann perimetry, a group of patients with complete temporal hemianopia on

  15. Short-wavelength perimetry in diagnosis of early glaucoma: comparison with standard automated perimetry%蓝/黄视野计与标准白色视野计检测早期青光眼的敏感性比较

    Institute of Scientific and Technical Information of China (English)

    齐绍文; 蒋幼芹

    2002-01-01

    目的探讨蓝/黄视野计(blue-on-yellow perimetry,B/Y)又称短波视野计(short-wavelength perimetry)及自动标准白色视野计(white-on-white perimetry,W/W)检测早期青光眼的敏感性.方法采用自行改装的德国Twinfield视野计,对36例(46只眼)早期原发性开角型青光眼患者及38例对照组正常人(46只眼)进行B/Y及W/W检测,两组的年龄及性别相匹配.视野检查采用24-2程序,将中心25°内全视网膜光敏感度均值及各象限光敏感度均值(dB值)进行组间比较和分析.结果两种视野计检测正常人,B/Y较W/W检测全视网膜光敏感度均值低,差异有显著意义(t=3.57,P颞下>鼻上>颞上;以B/Y检测出的视野缺损面积大且深.按视岛(island of vision) 矫正的偏差图(corrected deviation)计算P<0.05以上的缺损点数,显示B/Y>W/W检测结果,前者为后者的2.6倍,差异有显著意义(χ2=226.72,P<0.001).46只早期青光眼中,B/Y检测视野异常者40只眼,阳性率为87%;W/W检测视野异常者31只眼,阳性率为67%;两种视野计检测出的异常阳性率差异有显著意义(u=3.22,P<0.05).结论 B/Y与W/W检测结果有良好的符合性.检测早期青光眼性视野改变,B/Y较W/W敏感,表现为早期青光眼的异常检出率高,检测出的视野缺损范围大且深.

  16. A Randomized, Double-Blind, Placebo-Controlled Clinical Trial Using a Low-Frequency Magnetic Field in the Treatment of Musculoskeletal Chronic Pain

    Directory of Open Access Journals (Sweden)

    Alex W Thomas

    2007-01-01

    Full Text Available Exposure to a specific pulsed electromagnetic field (PEMF has been shown to produce analgesic (antinociceptive effects in many organisms. In a randomized, double-blind, sham-controlled clinical trial, patients with either chronic generalized pain from fibromyalgia (FM or chronic localized musculoskeletal or inflammatory pain were exposed to a PEMF (400 μT through a portable device fitted to their head during twice-daily 40 min treatments over seven days. The effect of this PEMF on pain reduction was recorded using a visual analogue scale. A differential effect of PEMF over sham treatment was noticed in patients with FM, which approached statistical significance (P=0.06 despite low numbers (n=17; this effect was not evident in those without FM (P=0.93; n=15. PEMF may be a novel, safe and effective therapeutic tool for use in at least certain subsets of patients with chronic, nonmalignant pain. Clearly, however, a larger randomized, double-blind clinical trial with just FM patients is warranted.

  17. Laboratory Measurements of Multi-Frequency and Broadband Acoustic Scattering from Turbulent and Double-Diffusive Microstructure. High-Frequency Broadband Acoustic Scattering from Non-Linear Internal Waves during SW06

    Science.gov (United States)

    2010-05-27

    1996; Nero et al, 1998; Love et al, 2004). The broadband system developed for this project was used to measure high-frequency broadband acoustic...Wilson, M. A., and Nero , R.W. (2004). "Unusual swimbladder behavior offish in the Cariaco Trench," Deep-Sea Research 151(1): 1-16. Lundgren B., and...propagating shoreward over the continental shelf," J. Phys. Oceanogr. 33, 2093-2112. Nero , R.W., Thompson, C.H., and Love, R.H. (1998). "Low-frequency

  18. All-solid-state extracavity double-frequency laser for 355 mn UV source%用于355nm紫外光源的腔外倍频全固态激光器

    Institute of Scientific and Technical Information of China (English)

    耿爱丛; 赵慈; 李宝河; 徐登辉; 李熊

    2011-01-01

    The purpose of this study is to ensure high output power and high beam quality of 1064 nm and 532 nm laser collinear output. Firstly, the beam quality of 1064 nm laser fundamental frequency was effectively controlled by using a master oscillator and power amplifier (MOPA) ,to achieve maximum average power of 70 W,repetition rate of 10 kHz,pulse width of 60 ns,and beam quality factor/MF of 3. 9.Then using two power amplifiers, a 1 064 nm beam with average output power of 182.9 W and pulse width of 80 ns was generated. Finally, by extra-cavity double-frequency generation with a KTP crystal,which ensures that fundamental laser and double-frequency laser are isochronous and collinear, a green laser at 532 nm with average power of 65.7W and pulse width of about 60 ns was obtained. The corresponding frequency-doubling effidency is 35.9% ,and green beam quality M2 is controlled at 6.%为保证高输出功率前提下获得高光束质量的1064和532 nm激光共向输出,实验中,首先采用主振荡功率放大器系统有效地控制基频光束质量,获得平均功率为70 W、重复频率为10 kHz、脉宽为60 ns和光束质量因子M2约为3.9的1064 nm基频激光;接着利用二级放大器,获得平均功率为182.9 W,脉宽为80 ns的1064nm激光.然后,采用KTP晶体腔外倍频技术保证了基频和倍频激光同时、共向输出,最终获得了平均功率为65.7 W、脉宽约为60 ns的532 nm绿光,相应的倍频效率为35.9%.通过有效措施,绿光的光束质量因子M2约控制在6,为开展355 nm紫外激光研究奠定了良好的基础.

  19. 基于布里渊载波相移的宽带可调谐二倍频微波信号生成*%Widely tunable frequency-doubling microwaves generated using Brillouin-assisted carrier phase shift

    Institute of Scientific and Technical Information of China (English)

    郑狄; 潘炜; 闫连山; 罗斌; 邹喜华; 刘新开; 易安林

    2014-01-01

    本文提出并实验验证了一种基于光纤中受激布里渊散射效应的光子二倍频微波信号生成技术。利用布里渊增益谱内的强色散特性,对光强度调制器产生的双边带调制信号的载波进行π/2相移,可实现载波与±1阶边带拍频仅生成二倍频微波信号。由于光纤中受激布里渊散射的窄带特性以及仅对双边带调制信号的载波进行相移,不影响调制信号两个边带的幅值和相位,因而生成的二倍频微波信号可实现宽带调谐,调谐范围仅受其他光器件的工作带宽限制。此外,信号光和产生受激布里渊散射的抽运光均来自同一光源,因而不受波长漂移的影响,系统具良好的稳定性。%An optically tunable frequency-doubling microwave generation technique based on stimulated Brillouin scattering (SBS) in optical fibers is proposed and experimentally demonstrated. Due to the strong dispersion characteristics in SBS, when a π/2 phase shift is imposed on the optical carrier of an amplitude-modulated signal by SBS, only a frequency-doubling microwave signal from the beating between the optical carrier and the ±1st sidebands is generated. Due to the inherent narrowband character of SBS and the phase shift being only imported on to the optical carrier while the sidebands are kept unchanged, the frequency-doubling with large frequency tunability is realized, the operational bandwidth is just limited by other optical device deployed. In addition, all the required optical signals and pumps can be generated from the same laser source, the influence from the wavelength drifting is eliminated, so the stability of the system is established.

  20. Flicker perimetry in healthy subjects: influence of age and gender, learning effect and short-term fluctuation Perimetria "flicker" em indivíduos normais: influência da idade e sexo, efeito aprendizado e flutuação a curto prazo

    Directory of Open Access Journals (Sweden)

    Luciana Bernardi

    2007-02-01

    Full Text Available PURPOSE: To determine the mean critical fusion frequency and the short-term fluctuation, to analyze the influence of age, gender, and the learning effect in healthy subjects undergoing flicker perimetry. METHODS: Study 1 - 95 healthy subjects underwent flicker perimetry once in one eye. Mean critical fusion frequency values were compared between genders, and the influence of age was evaluated using linear regression analysis. Study 2 - 20 healthy subjects underwent flicker perimetry 5 times in one eye. The first 3 sessions were separated by an interval of 1 to 30 days, whereas the last 3 sessions were performed within the same day. The first 3 sessions were used to investigate the presence of a learning effect, whereas the last 3 tests were used to calculate short-term fluctuation. RESULTS: Study 1 - Linear regression analysis demonstrated that mean global, foveal, central, and critical fusion frequency per quadrant significantly decreased with age (p0.05, with the exception of the central area and inferonasal quadrant (p=0.049 and p=0.011, respectively, where the values were lower in females. Study 2 - Mean global (p=0.014, central (p=0.008, and peripheral (p=0.03 critical fusion frequency were significantly lower in the first session compared to the second and third sessions. The mean global short-term fluctuation was 5.06±1.13 Hz, the mean interindividual and intraindividual variabilities were 11.2±2.8% and 6.4±1.5%, respectively. CONCLUSION: This study suggests that, in healthy subjects, critical fusion frequency decreases with age, that flicker perimetry is associated with a learning effect, and that a moderately high short-term fluctuation is expected.OBJETIVOS: Determinar os valores médios da freqüência crítica de fusão e a flutuação a curto prazo, analisar a influência da idade, sexo e o efeito aprendizado na perimetria "flicker". MÉTODOS: Estudo 1 - 96 indivíduos normais foram submetidos à perimetria "flicker" uma vez em

  1. Renormalized phonon frequencies and electric resistivity along the c-axis in single-plane high-temperature superconductors: A double-well analysis

    CERN Document Server

    Georgiev, M; Polyanski, I; Petrova, P T; Tsintsarska, S; Gochev, A

    2001-01-01

    We consider the dynamic interlayer charge transfer across apex oxygens between CuO sub 2 planes in single-layered high-T sub c superconductors. Phonon-coupled axial transfer rates are derived by means of the reaction-rate method. They lead straightforwardly to temperature dependences for the axial resistivity. Doping and temperature dependences are also derived for the renormalized frequencies of phonon modes coupled to the interlayer charge transfer. Our results are compared with experimentally observed dependences. (author)

  2. 2.1-watts intracavity-frequency-doubled all-solid-state light source at 671 nm for laser cooling of lithium

    CERN Document Server

    Eismann, Ulrich; Salomon, Christophe; Chevy, Frédéric

    2013-01-01

    We present an all-solid-state laser source emitting up to 2.1 W of single-frequency light at 671 nm developed for laser cooling of lithium atoms. It is based on a diode-pumped, neodymium-doped orthovanadate (Nd:YVO$_4$) ring laser operating at 1342 nm. Optimization of the thermal management in the gain medium results in a maximum multi-frequency output power of 2.5 W at the fundamental wavelength. We develop a simple theory for the efficient implementation of intracavity second harmonic generation, and its application to our system allows us to obtain nonlinear conversion efficiencies of up to 88%. Single-mode operation and tuning is established by adding an etalon to the resonator. The second-harmonic wavelength can be tuned over 0.5 nm, and mode-hop-free scanning over more than 6 GHz is demonstrated, corresponding to around ten times the laser cavity free spectral range. The output frequency can be locked with respect to the lithium $D$-line transitions for atomic physics applications. Furthermore, we obser...

  3. 2.1-watts intracavity-frequency-doubled all-solid-state light source at 671 nm for laser cooling of lithium.

    Science.gov (United States)

    Eismann, U; Bergschneider, A; Sievers, F; Kretzschmar, N; Salomon, C; Chevy, F

    2013-04-08

    We present an all-solid-state laser source emitting up to 2.1 W of single-frequency light at 671 nm developed for laser cooling of lithium atoms. It is based on a diode-pumped, neodymium-doped orthovanadate (Nd:YVO(4)) ring laser operating at 1342 nm. Optimization of the thermal management in the gain medium results in a maximum multi-frequency output power of 2.5 W at the fundamental wavelength. We develop a simple theory for the efficient implementation of intracavity second harmonic generation, and its application to our system allows us to obtain nonlinear conversion efficiencies of up to 88%. Single-mode operation and tuning is established by adding an etalon to the resonator. The second-harmonic wavelength can be tuned over 0.5 nm, and mode-hop-free scanning over more than 6 GHz is demonstrated, corresponding to around ten times the laser cavity free spectral range. The output frequency can be locked with respect to the lithium D-line transitions for atomic physics applications. Furthermore, we observe parametric Kerr-lens mode-locking when detuning the phase-matching temperature sufficiently far from the optimum value.

  4. Safety of variable double-frequency Nd∶ YAG laser in treatment of skin vascular disease%可调脉宽倍频Nd∶YAG激光治疗皮肤血管性疾病安全性探讨

    Institute of Scientific and Technical Information of China (English)

    于云和

    2015-01-01

    Objective To investigate the safety of variable double-frequency Nd∶ YAG laser in treatment of skin vascular disease,and provide reliable reference data for clinical treatment.Methods One hundred and twenty-two patients with skin vascular diseases in people' s hospital of Xinye from May 2011 to April 2013 were randomly divided into control group and observation group,with 61 cases in each group.The control group underwent intense pulsed light therapy,the observation group underwent variable double-frequency Nd∶ YAG laser therapy.The clinical efficacy and safety were compared between the two groups.Results The total effective rates of telangiectasia,spider always,hemangiomas and port wine stains,and the incidence of adverse reactions in observation group were better than that in the control group,the differences were statistically significant (all P < 0.05).Conclusions Variable double-frequency Nd∶ YAG laser in treatment of skin vascular disease has significant effect,and the operation is simple,safe,it should be widely applied in clinic.%目的 探讨可调脉宽倍频Nd∶YAG激光治疗皮肤血管性疾病的安全性,旨在为临床治疗提供可靠的参考数据.方法 选取新野县人民医院2011年5月至2013年4月收治的皮肤血管性疾病患者122例,随机分为对照组及观察组,每组61例.对照组采用强脉冲光治疗,观察组采用可调脉宽倍频Nd∶YAG激光治疗,比较两组的临床疗效及安全性.结果 观察组治疗毛细血管扩张、蜘蛛痣、血管瘤、鲜红斑痣的总有效率及不良反应均优于对照组,差异均有统计学意义(P<0.05).结论 可调脉宽倍频Nd∶YAG激光对于治疗各种皮肤血管性疾病有显著的疗效,且操作简便,安全性高,值得临床推广应用.

  5. I-SceI-mediated double-strand break does not increase the frequency of homologous recombination at the Dct locus in mouse embryonic stem cells.

    Science.gov (United States)

    Fenina, Myriam; Simon-Chazottes, Dominique; Vandormael-Pournin, Sandrine; Soueid, Jihane; Langa, Francina; Cohen-Tannoudji, Michel; Bernard, Bruno A; Panthier, Jean-Jacques

    2012-01-01

    Targeted induction of double-strand breaks (DSBs) at natural endogenous loci was shown to increase the rate of gene replacement by homologous recombination in mouse embryonic stem cells. The gene encoding dopachrome tautomerase (Dct) is specifically expressed in melanocytes and their precursors. To construct a genetic tool allowing the replacement of Dct gene by any gene of interest, we generated an embryonic stem cell line carrying the recognition site for the yeast I-SceI meganuclease embedded in the Dct genomic segment. The embryonic stem cell line was electroporated with an I-SceI expression plasmid, and a template for the DSB-repair process that carried sequence homologies to the Dct target. The I-SceI meganuclease was indeed able to introduce a DSB at the Dct locus in live embryonic stem cells. However, the level of gene targeting was not improved by the DSB induction, indicating a limited capacity of I-SceI to mediate homologous recombination at the Dct locus. These data suggest that homologous recombination by meganuclease-induced DSB may be locus dependent in mammalian cells.

  6. I-SceI-mediated double-strand break does not increase the frequency of homologous recombination at the Dct locus in mouse embryonic stem cells.

    Directory of Open Access Journals (Sweden)

    Myriam Fenina

    Full Text Available Targeted induction of double-strand breaks (DSBs at natural endogenous loci was shown to increase the rate of gene replacement by homologous recombination in mouse embryonic stem cells. The gene encoding dopachrome tautomerase (Dct is specifically expressed in melanocytes and their precursors. To construct a genetic tool allowing the replacement of Dct gene by any gene of interest, we generated an embryonic stem cell line carrying the recognition site for the yeast I-SceI meganuclease embedded in the Dct genomic segment. The embryonic stem cell line was electroporated with an I-SceI expression plasmid, and a template for the DSB-repair process that carried sequence homologies to the Dct target. The I-SceI meganuclease was indeed able to introduce a DSB at the Dct locus in live embryonic stem cells. However, the level of gene targeting was not improved by the DSB induction, indicating a limited capacity of I-SceI to mediate homologous recombination at the Dct locus. These data suggest that homologous recombination by meganuclease-induced DSB may be locus dependent in mammalian cells.

  7. Green Output of 1.5 W from a Diode-Pumped Intracavity Frequency-Doubled Self-Q-Switched and Mode-Locked Cr,Nd:YAG Laser

    Institute of Scientific and Technical Information of China (English)

    DU Shi-Feng; WANG Su-Mei; ZHANG Dong-Xiang; LI De-Hua; ZHANG Zhi-Guo; FENG Bao-Hua; ZHANG Shi-Wen

    2007-01-01

    We report a diode-pumped intracavity frequency-doubled self-Q-switched and mode-locked Cr,Nd:YAG/KTP green laser with a Z-type cavity, which produces 1.5 W of average power at 532 nm with incident pump power 14.2 W. The individual mode-locked green pulse duration is about 560ps with 149MHz repetition rate. Almost 100% modulation depth of the mode-locked green pulses is achieved at an incident pump power of 4.13 W. The maximum energy of Q-switched green pulse is 19.8 fiJ. The experimental results of pulse duration and pulse energy of Q-switched green pulse agree well with the theoretical calculations.

  8. Effect of 0.2% Chlorhexidine Gel on Frequency of Dry Socket Following Mandibular Third Molar Surgery: A Double-Blind Clinical Trial Clinical Trial

    Directory of Open Access Journals (Sweden)

    Baratollah Shaban

    2014-09-01

    Full Text Available Introduction: Alveolar osteitis (AO is one of the most common postoperative complications after third molar surgery. Various techniques have been used to reduce the risk of AO. The aim of the current study was to evaluate the effect of Chlorhexidine (CHX bioadhesive gel in preventing the development of AO. Methods: Patients with bilateral impacted mandibular third molars underwent surgical extraction of both teeth. One socket was randomly received CHX gel and the contralateral socket served as the control. The outcome variable was development of AO and the CHX gel application was the predictor variable. Data were analyzed using chi-square test with the confidence interval of 95%. Results: 41 patients (27 females and 14 males with mean age of 24.15 ± 5.02 years underwent 82 surgeries. Total of 11 sockets (13.41% developed AO. The frequency of AO in CHX gel (2 cases, 4.87% side was significantly lower than control (9 cases, 21.95% side (P-value < 0.05. No side effects observed following CHX gel application. Conclusion: Application of CHX gel could be an effective approach to reduce the risk of developing AO following mandibular third molar surgery.

  9. Effect of Low-Frequency Repetitive Transcranial Magnetic Stimulation on Naming Abilities in Early-Stroke Aphasic Patients: A Prospective, Randomized, Double-Blind Sham-Controlled Study

    Directory of Open Access Journals (Sweden)

    Konrad Waldowski

    2012-01-01

    Full Text Available Background and Purpose. Functional brain imaging studies with aphasia patients have shown increased cortical activation in the right hemisphere language homologues, which hypothetically may represent a maladaptive strategy that interferes with aphasia recovery. The aim of this study was to investigate whether low-frequency repetitive transcranial magnetic stimulation (rTMS over the Broca’s homologues in combination with speech/language therapy improves naming in early-stroke aphasia patients. Methods. 26 right-handed aphasic patients in the early stage (up to 12 weeks of a first-ever left hemisphere ischemic stroke were randomized to receive speech and language therapy combined with real or sham rTMS. Prior to each 45-minute therapeutic session (15 sessions, 5 days a week, 30 minutes of 1-Hz rTMS was applied. Outcome measures were obtained at baseline, immediately after 3 weeks of experimental treatment and 15 weeks; posttreatment using the Computerized Picture Naming Test. Results. Although both groups significantly improved their naming abilities after treatment, no significant differences were noted between the rTMS and sham stimulation groups. The additional analyses have revealed that the rTMS subgroup with a lesion including the anterior part of language area showed greater improvement primarily in naming reaction time 15 weeks after completion of the therapeutic treatment. Improvement was also demonstrated in functional communication abilities. Conclusions. Inhibitory rTMS of the unaffected right inferior frontal gyrus area in combination with speech and language therapy cannot be assumed as an effective method for all poststroke aphasia patients. The treatment seems to be beneficial for patients with frontal language area damage, mostly in the distant time after finishing rTMS procedure.

  10. Structure-Function Modeling of Optical Coherence Tomography and Standard Automated Perimetry in the Retina of Patients with Autosomal Dominant Retinitis Pigmentosa.

    Directory of Open Access Journals (Sweden)

    Travis B Smith

    Full Text Available To assess relationships between structural and functional biomarkers, including new topographic measures of visual field sensitivity, in patients with autosomal dominant retinitis pigmentosa.Spectral domain optical coherence tomography line scans and hill of vision (HOV sensitivity surfaces from full-field standard automated perimetry were semi-automatically aligned for 60 eyes of 35 patients. Structural biomarkers were extracted from outer retina b-scans along horizontal and vertical midlines. Functional biomarkers were extracted from local sensitivity profiles along the b-scans and from the full visual field. These included topographic measures of functional transition such as the contour of most rapid sensitivity decline around the HOV, herein called HOV slope for convenience. Biomarker relationships were assessed pairwise by coefficients of determination (R2 from mixed-effects analysis with automatic model selection.Structure-function relationships were accurately modeled (conditional R(2>0.8 in most cases. The best-fit relationship models and correlation patterns for horizontally oriented biomarkers were different than vertically oriented ones. The structural biomarker with the largest number of significant functional correlates was the ellipsoid zone (EZ width, followed by the total photoreceptor layer thickness. The strongest correlation observed was between EZ width and HOV slope distance (marginal R(2 = 0.85, p<10(-10. The mean sensitivity defect at the EZ edge was 7.6 dB. Among all functional biomarkers, the HOV slope mean value, HOV slope mean distance, and maximum sensitivity along the b-scan had the largest number of significant structural correlates.Topographic slope metrics show promise as functional biomarkers relevant to the transition zone. EZ width is strongly associated with the location of most rapid HOV decline.

  11. Double Trouble

    NARCIS (Netherlands)

    Elsaesser, Thomas; Kievit, Robert; Simons, Jan

    1994-01-01

    Double Trouble highlights the career of Dutch scriptwriter and television producer Chiem van Houweninge, well-known for his long-running TV comedy series and as author of episodes for TV detective series. Double Trouble gives Van Houweninge's own views on writing and filming in television prime impo

  12. Double Trouble

    NARCIS (Netherlands)

    Elsaesser, Thomas; Kievit, Robert; Simons, Jan

    1994-01-01

    Double Trouble highlights the career of Dutch scriptwriter and television producer Chiem van Houweninge, well-known for his long-running TV comedy series and as author of episodes for TV detective series. Double Trouble gives Van Houweninge's own views on writing and filming in television prime

  13. 激光联合依帕司他治疗糖尿病视网膜病变%The clinical effect of combining double frequency laser of 523 nm with Epalrestat tablets for therapy of diabetic retinopathy

    Institute of Scientific and Technical Information of China (English)

    冯军; 严晓腾; 康建芳

    2012-01-01

    目的 观察应用倍频532激光联合口服依帕司他(epalrestat)治疗糖尿病视网膜病变的有效性及安全性.方法 64例糖尿病视网膜病变,随机分为两组.观察组32例(55眼),采用倍频532激光治疗的同时口服依帕司他,激光治疗每周1次,连续4次,口服依帕司他50 mg,3次/d,持续至激光治疗结束后3个月.对照组32例(58眼),单纯采用激光治疗,方法同观察组.两组患者均采用原有的降血糖及降血压等内科治疗,空腹血糖<7 mm ol/L,血压在140/90 mm Hg以下.激光治疗结束后随访3个月,观察两组在视功能改善,视网膜新生血管消退及黄斑水肿吸收等方面的差异.结果 观察组在视功能改善,视网膜新生血管消退及黄斑水肿吸收等方面均优于对照组(P<0.05).结论 倍频532激光联合依帕司他治疗糖尿病视网膜病变较单纯应用倍频532激光治疗具有更好的临床效果.%Objective To observe the efficacy and safety of the double frequency laser of 523 nm combined with Epalrestat tablets for therapy of diabetic retinopathy.Methods 64 cases with diabetic retinopathy were randomly divided into the experimental group (32 cases,55 eyes) and the control group (32cases,58 eyes).Combination of the double frequency laser of 523 nm with Epalrestat tablets were adopted in the experimental group,and the simple laser was used in the control group.The laser therapy was applied with four times (one time per week),and Epalrestat tablets (50mg,three times per day) were used for three months of the end of the laser therapy.The medical treatment of controlling blood glucose and blood pressure was carried out in two groups.All cases were followed up three months after the laser therapy and were evaluated in aspects of the improvement of visual function,the alleviation of retina neovessels and the absorption of macular edema.Results Cases of the experimental group were superior to the control group in aspects of the improvement of

  14. Models of Intracavity Frequency Doubled Lasers

    Science.gov (United States)

    1990-01-01

    maps in Fig. 3.170)). The aperiodic nature of a chaotic trajectory is further characterized by a broad FFT. A broad- banded spectrum can also be...YAG as a two-level transition (Fig. 1.3). There are actually four energy bands or levels involved in the process, but we assume that two of the decay...8217(/" INPUT RELATIVE LOSS FRACTION") ’) READ(*, ’(F6.4) ’) FLOSS GAM1= FLOSS *GAM2 GAM3 =GAM1 C GAM=4 .E3 GAMO=2 .E6 GOG=GAMO /GAM C SEC-INVERSE

  15. Frequency Doubling Nanocrystals for Cancer Theranostics

    CERN Document Server

    Staedler, Davide; Passemard, Solène; Schwung, Sebastian; Dubled, Marc; Schneiter, Guillaume Stéphane; Rytz, Daniel; Gerber-Lemaire, Sandrine; Bonacina, Luigi; Wolf, Jean-Pierre

    2013-01-01

    A novel bio-photonics approach based on the nonlinear optical process of second harmonic generation by non-centrosymmetric nanoparticles is presented and demonstrated on malignant human cell lines. The proposed method allows to directly interact with DNA in absence of photosensitizing molecules, to enable independent imaging and therapeutic modalities switching between the two modes of operation by simply tuning the excitation laser wavelength, and to avoid any risk of spontaneous activation by any natural or artificial light source.

  16. Spectral analysis of double-sampling switched-capacitor filters

    NARCIS (Netherlands)

    Rijns, J.J.F.; Rijns, J.J.F.; Wallinga, Hans

    1991-01-01

    The double-sampling scheme (DSS) design technique is suitable for the realization of high-frequency switched-capacitor (SC) filters. This design technique effectively doubles the applicable frequency range of standard bi-phase SC filters. In practice, the particular nonideal properties of the double

  17. Study on interaction between palladium(ІІ)-Linezolid chelate with eosin by resonance Rayleigh scattering, second order of scattering and frequency doubling scattering methods using Taguchi orthogonal array design

    Science.gov (United States)

    Thakkar, Disha; Gevriya, Bhavesh; Mashru, R. C.

    2014-03-01

    Linezolid reacted with palladium to form 1:1 binary cationic chelate which further reacted with eosin dye to form 1:1 ternary ion association complex at pH 4 of Walpole's acetate buffer in the presence of methyl cellulose. As a result not only absorption spectra were changed but Resonance Rayleigh Scattering (RRS), Second-order Scattering (SOS) and Frequency Doubling Scattering (FDS) intensities were greatly enhanced. The analytical wavelengths of RRS, SOS and FDS (λex/λem) of ternary complex were located at 538 nm/538 nm, 240 nm/480 nm and 660 nm/330 nm, respectively. The linearity range for RRS, SOS and FDS methods were 0.01-0.5 μg mL-1, 0.1-2 μg mL-1 and 0.2-1.8 μg mL-1, respectively. The sensitivity order of three methods was as RRS > SOS > FDS. Accuracy of all methods were determined by recovery studies and showed recovery between 98% and 102%. Intraday and inter day precision were checked for all methods and %RSD was found to be less than 2 for all methods. The effects of foreign substances were tested on RRS method and it showed the method had good selectivity. For optimization of process parameter, Taguchi orthogonal array design L8(24) was used and ANOVA was adopted to determine the statistically significant control factors that affect the scattering intensities of methods. The reaction mechanism, composition of ternary ion association complex and reasons for scattering intensity enhancement was discussed in this work.

  18. Comparitive Study of the Threshold Variability between Blue-on-yellow Perimetry and White-on-white Perimetry%蓝/黄视野检查法和白/白视野检查法阈值变异的对比研究

    Institute of Scientific and Technical Information of China (English)

    钟一声; 叶纹; 高骏; 俞方知; 王康孙

    2002-01-01

    目的:比较蓝/黄视野检查法[Blue-on-yellow(B/Y)perimetry]和白/白视野检查法[White-on-white(W/W)perimetry]阈值变异的情况,评价B/Y视野检查法的可重复性.方法:应用Octopus 101全自动视野计分别对12例(24眼)正常人、16例(32眼)原发性开角型青光眼(Primary open angle glaucoma,POAG)和7例(14眼)可疑POAG患者分别进行B/Y视野检查和W/W视野检查.所有受检者在2周内再次分别进行上述两种视野检查.将两种视野检查的阈值进行点对点阈值变异分析和比较.结果:在所有受检者中,B/Y视野检查的全视野总的平均阈值变异(2.61±0.94)decibels(dB)大于W/W视野检查的阈值变异(2.11±0.90)dB,但差异无显著性意义(P=0.6244).正常人B/Y视野检查的全视野总的平均阈值变异(2.07±0.54)dB明显大于W/W视野检查的阈值变异(1.50±0.34)dB(P=0.0006),而可疑POAG和POAG组,两种视野检查的全视野总的平均阈值变异差异无显著性意义(P=0.0523和0.9371).正常人和可疑POAG组中,有部分离心度处的阈值变异,两种视野检查法之间差异有显著性意义,而在POAG组中,两种视野检查法各相应离心度之间差异均无显著性意义.结论:正常人B/Y视野检查的阈值变异大于W/W视野检查的阈值变异,而可疑POAG和POAG患者B/Y视野检查的阈值变异与W/W视野检查的阈值变异差异均无显著性意义.

  19. 蓝/黄视野计与标准白色视野计在早期青光眼诊断中的意义%The comparison of blue - on - yellow perimetry with standard white - on - white perimetry on the early diagnosis of primary open angle glaucoma

    Institute of Scientific and Technical Information of China (English)

    常宝琴; 石一宁; 徐琨; 王米仓; 吕沛霖

    2003-01-01

    目的:评价蓝/黄视野计(blue-on-yellow perimetry,B/Y)又叫短波视野计short-wavelength perimetry与标准白色视野计(whiteon-white perimetry,W/W)检测早期青光眼的敏感性.方法:采用瑞士产Octopus 101型全自动视野计对早期原发性开角型青光眼17例34只眼,对照组正常人8例16只眼,进行B/Y及W/W检测,视野检测采用tG2测试程序,将中心30°视野内全视网膜光敏感度均值及各象限光敏感度均值(dB)进行比较分析.结果:两种视野计检测正常人B/Y较W/W检测全视网膜光敏感度均值低,两者相差3.96dB,差异有显著意义(t=5.11,P<0.001),对应各象限视网膜光敏感度均值比较,差异均有显著意义(P<0.001),早期开角型青光眼B/Y较W/W检测全视网膜光敏感度均值差为5.34dB,差异有显著意义(t=5.87,P<0.001),对应各象限视网膜光敏感度均值差5dB以上,差异有显著性(P<0.001),视网膜光敏感度均值依次为鼻下>颞下>鼻上>颞上,以B/Y检测出的缺损面积大且深,按矫正偏差图(corrected probability)计算P<2以上缺损点数,显示B/Y检测结果大于W/W检测结果,前者为后者的2.23倍,差异有显著意义(X2=13.04,P<0.005),早期开角型青光眼组34只眼B/Y检测视野阳性者24只眼,阳性率为70.59%,W/W检测视野阳性者14只眼,阳性率为41.18%,两种视野计检测结果的异常率有显著差异(X2=5.33,P<0.005).结论:B/Y与W/W检测结果有良好的一致性,检测早期开角型青光眼的视野改变B/Y较W/W敏感,表现为早期青光眼检测阳性率高,检测出的视野缺损范围大而且深.

  20. [Practical aspects of automated perimetry].

    Science.gov (United States)

    Stan, Cristina

    2014-01-01

    Visual field testing is a subjective method, but yet a very important part for diagnosis and in follow-up of ocular or neurological diseases. In order to do a correct exam of the visual field, one must know well the equipment and all the factors that could induce errors. Basic skills for working with Optopol or Humphrey perimeter are discussed in this paper.

  1. Background illumination and automated perimetry.

    Science.gov (United States)

    Klewin, K M; Radius, R L

    1986-03-01

    Visual field function in the right and left eyes of 31 normal volunteers was evaluated with an automated projection perimeter (OCTOPUS). Serial visual field evaluations were repeated in these same eyes with neutral filters of increasing optical density. We compared the results of threshold determinations with the different neutral filters in place before the examined eye. Significant reduction in threshold sensitivity at several test spots throughout the central 30 degrees visual field was seen with neutral density filters of 0.5 log units or greater. The low level of background illumination of the OCTOPUS perimeter (4.0 apostilbs) may allow relatively minor reduction in light transmission by the ocular media to produce significant changes in the recorded level of threshold sensitivity during visual field evaluation.

  2. Double supergeometry

    CERN Document Server

    Cederwall, Martin

    2016-01-01

    A geometry of superspace corresponding to double field theory is developed, with type II supergravity in D=10 as the main example. The formalism is based on an orthosymplectic extension OSp(d,d|2s) of the continuous T-duality group. Covariance under generalised super-diffeomorphisms is manifest. Ordinary superspace is obtained as a solution of the orthosymplectic section condition. A systematic study of curved superspace Bianchi identities is performed, and a relation to a double pure spinor superfield cohomology is established. A Ramond-Ramond superfield is constructed as an infinite-dimensional orthosymplectic spinor. Such objects in minimal orbits under the OSp supergroup ("pure spinors") define super-sections.

  3. Double screening

    Energy Technology Data Exchange (ETDEWEB)

    Gratia, Pierre [Department of Physics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Hu, Wayne [Department of Astronomy and Astrophysics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Enrico Fermi Institute and Kavli Institute for Cosmological Physics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Joyce, Austin [Enrico Fermi Institute and Kavli Institute for Cosmological Physics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Ribeiro, Raquel H. [School of Physics and Astronomy, Queen Mary University of London,Mile End Road, London, E1 4NS (United Kingdom)

    2016-06-15

    Attempts to modify gravity in the infrared typically require a screening mechanism to ensure consistency with local tests of gravity. These screening mechanisms fit into three broad classes; we investigate theories which are capable of exhibiting more than one type of screening. Specifically, we focus on a simple model which exhibits both Vainshtein and kinetic screening. We point out that due to the two characteristic length scales in the problem, the type of screening that dominates depends on the mass of the sourcing object, allowing for different phenomenology at different scales. We consider embedding this double screening phenomenology in a broader cosmological scenario and show that the simplest examples that exhibit double screening are radiatively stable.

  4. Broadband frequency conversion

    DEFF Research Database (Denmark)

    Sanders, Nicolai Højer; Jensen, Ole Bjarlin; Dam, Jeppe Seidelin;

    that ensures phase matching over a broad spectral range in the BBO crystal. Since the tuning mechanism relies on all-passive components with extremely short response times the proposed method is well suited for short pulse, broad bandwidth laser sources like mode-locked lasers or super-continuum sources......We demonstrate a method for frequency conversion of broadly tunable or broad bandwidth light in a static, passive setup. Using simple optical components like lenses, mirrors and gratings and a BiBO crystal as the nonlinear material, we are able to frequency double a single-frequency, tunable...

  5. Double Dirac cones in phononic crystals

    KAUST Repository

    Li, Yan

    2014-07-07

    A double Dirac cone is realized at the center of the Brillouin zone of a two-dimensional phononic crystal (PC) consisting of a triangular array of core-shell-structure cylinders in water. The double Dirac cone is induced by the accidental degeneracy of two double-degenerate Bloch states. Using a perturbation method, we demonstrate that the double Dirac cone is composed of two identical and overlapping Dirac cones whose linear slopes can also be accurately predicted from the method. Because the double Dirac cone occurs at a relatively low frequency, a slab of the PC can be mapped onto a slab of zero refractive index material by using a standard retrieval method. Total transmission without phase change and energy tunneling at the double Dirac point frequency are unambiguously demonstrated by two examples. Potential applications can be expected in diverse fields such as acoustic wave manipulations and energy flow control.

  6. Double Imbalance

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The government has been introducing a string of policies to stabilize the economy and cushion the impact of the global eco-nomic slowdown since October.These policies are generally deemed"timely"and"necessary,"but not a long-term cure for problems in China’s economy.Renowned economist Wu Jinglian says the country must address its"double imbalance"and further reform its economic growth mode.He made his comments at the First Annual Global Management Forum on December 6 in Shanghai.Excerptsf ollow:

  7. Microfabricated ion frequency standard

    Science.gov (United States)

    Schwindt, Peter; Biedermann, Grant; Blain, Matthew G.; Stick, Daniel L.; Serkland, Darwin K.; Olsson, III, Roy H.

    2010-12-28

    A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.

  8. Double-Diffusive Convection in Rotational Shear

    Science.gov (United States)

    2015-03-01

    frequencies that conformed to the GM spectral model for internal waves with an initial random phase distribution, modeling an environment...shear wave field. This model used frequencies that conformed to the GM spectral model for internal waves with an initial random phase distribution...frequencies that conformed to the GM frequency spectral model. During this stage of research, double diffusion rates don’t stabilize into a single a steady

  9. Retrobulbar blood flow and visual field alterations after acute ethanol ingestion

    Directory of Open Access Journals (Sweden)

    Weber A

    2013-08-01

    Full Text Available Anke Weber, Andreas Remky, Marion Bienert, Klaudia Huber-van der Velden, Thomas Kirschkamp, Corinna Rennings, Gernot Roessler, Niklas Plange Department of Ophthalmology, RWTH Aachen University, Aachen, Germany Background: The purpose of this study was to test the effect of ethyl alcohol on the koniocellular and magnocellular pathway of visual function and to investigate the relationship between such visual field changes and retrobulbar blood flow in healthy subjects. Methods: In 12 healthy subjects (mean age 32 ± 4 years, color Doppler imaging, short-wavelength automated perimetry, and frequency doubling perimetry was performed before and 60 minutes after oral intake of 80 mL of 40 vol% ethanol. Mean and pattern standard deviations for short-wavelength automated and frequency doubling perimetry were assessed. End diastolic velocity (EDV and peak systolic velocity (PSV were measured in the central retinal and ophthalmic arteries using color Doppler imaging. Systemic blood pressure, heart rate, intraocular pressure, and blood alcohol concentration were determined. Results: Mean PSV and EDV in the central retinal artery showed a significant increase after alcohol intake (P = 0.03 and P = 0.02, respectively. Similarly, we found a significant acceleration of blood flow velocity in the ophthalmic artery (P = 0.02 for PSV; P = 0.04 for EDV. Mean intraocular pressure decreased by 1.0 mmHg after alcohol ingestion (P = 0.01. Retinal sensitivity in short-wavelength automated perimetry did not alter, whereas in frequency doubling perimetry, the mean deviation decreased significantly. Systolic and diastolic blood pressure did not change significantly. Mean blood alcohol concentration was 0.38 ± 0.16 g/L. Conclusion: Although ethanol is known to cause peripheral vasodilation, our subjects had no significant drop in systemic blood pressure. However, a significant increase of blood flow velocity was seen in the retrobulbar vessels. Regarding visual function

  10. A Comparative Study of Static Pseudorange Single Point Positioning by Double Frequency between BDS and GPS%北斗/GP S双频静态伪距单点定位结果对比分析∗

    Institute of Scientific and Technical Information of China (English)

    卢伟俊; 万庆涛; 范江涛; 张杰; 王晓岚; 李婧华; 马冠一

    2016-01-01

    BeiDou Navigation Satellite System ( BDS) was put into operation in Asian Pacific region in December 2012. To give a comprehensively comparative study of static pseudorange single point positioning between BDS and Global Positioning System (GPS), the double frequency data was sampled at 10s interval for 56h in Beijing in April 2014. The number of visible BDS satellites is larger than that of GPS. However, since BDS constellation is not finished yet, it has a positioning dilution of precision (PDOP) value of 2. 49, which is a little larger than that of GPS:2. 12. The standard error of unit weight is 2. 28m and 2. 50m for BDS and GPS, respectively. This indicates that BDS has a better psuedorange precision than GPS. The occurrence frequency of gross error is 0. 57%for BDS and 1. 02%for GPS, which shows that the usability of BDS is better than that of GPS. After removing the gross error, inner coincidence accuracy of BDS is better than that of GPS. It is 3. 24m in horizontal direction and 4. 40m in vertical direction for BDS. It is 3. 90m horizontally and 5. 47m vertically for GPS. But deviation between standard coordinate of BDS (8. 50m, 3. 73m, -0. 80m) is less satisfying than that of GPS (4. 50m, 2. 25m, 0. 56m), which means that BDS is better than GPS on stability but less accurate than GPS. It can be predicted that BDS will achieve better performance with the improvement and fulfillment of its constellation.%北斗卫星导航系统于2012年12月对亚太地区正式投入运行。为了对相关性能参数进行全面的分析比较,利用2014年4月在北京采集的观测时间56 h历元间隔10 s的原始双频数据,分别得到北斗与全球定位系统的静态伪距单点定位结果。北斗的可见卫星数多于全球定位系统,但是由于星座布局尚未完善,北斗的位置精度因子( Position Dilution of Precision, PDOP)均值为2.49,略大于全球定位系统的位置精度因子均值2.12。北斗的单位权中误差均值为2.28 m

  11. Clinical Analysis of the Change of Perimetry of 35 Cases with Visual Pathway Diseases%35例视路病变的视野改变与临床分析

    Institute of Scientific and Technical Information of China (English)

    吴仲新; 张文; 张金海; 朱国平; 朱萍; 王健利

    2012-01-01

    Objective To discuss the ophthalmological performance of visual pathway diseases, and enhance the early awareness of visual pathway diseases from the perspective of ophthalmology. Methods We analyzed the diseases sites, clinical manifestation and the results of perimetry of 35 cases with visual pathway diseases which had been definitely diagnosed by CT or MRI with their first outpatient services at Ophthalmology. Results There were 1 patient (2, 86%) experiencing pathological change at the area in front of chiasma, 8 patients (22. 86%) at optic chiasma, 8 patients (22. 86%) at the area behind chiasma and in front of occipital lobe, 18 patients (51.43%) at occipital lobe area. Thirty-four patients (97, 14%) said their major symptom were blurred vision and 6 patients (17. 14%) claimed themselves experiencing hemianopia. Thirty-four patients'(97. 14%) symptom were hemianopia. Among the 8 patients who had optic chiasma, there were 4 patients with 6 eyes had optic atrophy. Conclusion For those patients who said their major symptom was blurred vision or those patients experiencing discus opticus atrophy which cannot be explained by ophthalmological diseases, it should be regular to do the examination of perimetry and further CT/MRI examination should be made when it is necessary.%目的 探讨视路病变的眼科表现,从眼科角度提高对视路病变的早期认识.方法 分析首诊于眼科经CT或MRI确诊的35例视路病变的部位以及临床表现、视野检查结果.结果 视交叉前病变1例(2.86%),视交叉病变8例(22.86%),视交叉后枕叶前病变8例(22.86%),枕叶病变18例(51.43%).主诉视物模糊者34例(97.14%),有偏盲症状者6例(17.14%).视野检查有偏盲者34例(97.14%).8例视交叉疾病中4例6眼有视神经萎缩.结论 有视物模糊主诉或视乳头萎缩而无眼科病变可解释者,应把视野检查作为常规,必要时行CT/MRI检查.

  12. Influence of blue light spectrum filter on short-wavelength and standard automated perimetries Influência de filtro para o espectro azul da luz na perimetria computadorizada branco-branco e azul-amarelo

    Directory of Open Access Journals (Sweden)

    Leonardo Cunha Castro

    2006-10-01

    Full Text Available PURPOSE: To evaluate the influence of a blue light spectrum filter (BLSF, similar in light spectrum transmittance to the intraocular lens Acrysof NaturalTM, on standard automated perimetry (SAP and short-wavelength automated perimetry (SWAP. METHODS: Twenty young individuals (OBJETIVO: Avaliar a influência de um filtro para o espectro azul da luz, semelhante à lente intra-ocular Acrysof Natural®, nos exames de perimetria automatizada padrão (branco-no-branco e de comprimento de onda curto (azul-no-amarelo. MÉTODOS: Vinte pacientes jovens sem alterações oculares (20 olhos realizaram seqüência de 4 exames de campo visual: perimetria automatizada padrão e azul-no-amarelo com e sem o filtro para o espectro azul da luz. Os índices de limiar foveal (FT, desvio médio (MD e desvio-padrão (PSD obtidos em todos os exames e a diferença causada pela excentricidade nos exames de perimetria automatizada azul-no-amarelo foram analisados. Variabilidade interindivíduos (desvio-padrão dos pontos testados foi calculada. RESULTADOS: Observou-se redução estatisticamente significante no desvio médio (p<0.001 e no limiar foveal (p<0.001 medidos pela perimetria automatizada azul-no-amarelo com o uso do filtro para o espectro azul da luz comparado quando realizado sem o filtro. Nenhum outro índice avaliado apresentou diferença estatisticamente significante nos exames de perimetria automatizada padrão ou azul-no-amarelo. Foi notado aumento da variabilidade interindivíduos com a excentricidade nos exames de perimetria automatizada azul-no-amarelo com e sem o uso do filtro para o espectro azul da luz, assim como a diferença de sensibilidade entre os hemisférios inferior e superior (hemisfério inferior menos superior, mas não houve diferença estatisticamente significante quando comparados os exames com e sem o uso do filtro. Quando foram comparados os 4 pontos mais inferiores e os 4 pontos mais superiores, a diferença inferior-superior aumentou

  13. Double Conditional Expectation

    Institute of Scientific and Technical Information of China (English)

    HU Di-he

    2004-01-01

    The concept of double conditional expectation is introduced. A series of properties for the double conditional expectation are obtained several convergence theorems and Jensen inequality are proved. Finally we discuss the special cases and application for double conditional expectation.

  14. Spectral analysis of double-sampling switched-capacitor filters

    NARCIS (Netherlands)

    Rijns, J.J.F.; Rijns, J.J.F.; Wallinga, Hans

    1991-01-01

    The double-sampling scheme (DSS) design technique is suitable for the realization of high-frequency switched-capacitor (SC) filters. This design technique effectively doubles the applicable frequency range of standard bi-phase SC filters. In practice, the particular nonideal properties of the

  15. DEVELOPMENT OF HYDROLOGICAL CABLEWAY SAND CONTROL MEASUREMENT INSTRUMENT BASED ON THE DOUBLE AUDIO FREQUENCY SIGNAL CONTROL%基于双音频信号控制的水文缆道测沙自控仪的研制

    Institute of Scientific and Technical Information of China (English)

    康修洪; 李先哲; 肖英; 朱兵

    2015-01-01

    According to the automatic cable measurement instruments widely used in hydrologic station, which has some problems such as cannot measurement and sampling sediment normally, we carried out the development of hydrological cableway sand control measurement instrument. The automatic control instrument will organically combine double tube double steady water sample collected valves and lead fish, reasonable decorate into the drainage pipeline and communication lines, the horizontal and vertical of hydrological cableway operate accurate positions, with double audio signal to transmit reliable control subsea sampler valve switch, acquisition section of each location, different depth of water samples, and send back the valve switch status signal in time. Practice has proved that the adoption of double tube double steady water samples collected valves can solve the problem of inlet pipe alluvial sediment under closed pressure, at the same time valve no need to seal. It also implements the hydrological monitoring data two-way transmission control of the bank to the water and the water to the shore.%针对水文站中普遍使用的自动缆道测流仪器,均存在进水阀密封、信号控制、与缆道测流系统整合等诸多问题,研制了一种基于嵌入式的水文缆道测沙自控仪。该自控仪将双管双稳态水样采集阀门与铅鱼有机结合,合理布置进排水管线和通讯线路,水文缆道的水平和垂直运行准确定位,采用双音频信号传输可靠的控制水下采样器阀门的开关,测取断面各位置,不同水深的水样,并及时发回阀门开关状况信号。实践证明,由于采用了双管双稳态水样采集阀门解决了关闭状态下进水管淤积泥沙问题,同时阀门不必进行全密封,还实现了水文监测数据岸上至水中和水中至岸上的双向控制传输,研制的仪器获得成功应用。

  16. High Frequency Production of Doubled Haploid Rapeseed Plants by Direct Colchicine Treatment of Isolated Microspores%油菜小孢子秋水仙素直接处理增加纯合两倍体植株频率

    Institute of Scientific and Technical Information of China (English)

    周伟军; Per,H

    2000-01-01

    @@ Techniques for microspore culture of Brassica napus have been improved rapidly, and embryogenesis has been achieved in a wide range of genotypes. Plants regenerated from microspore-derived embryoids can be haploid, diploid or polyploid. From rapeseed microspore culture it is reported that 70%-90% of regenerated plants are haploid. The usual methods of chromosome doubling involve soaking roots (most common) or whole plants in a colchicine solution, or culturing plantlets in colchicine-containing medium in the greenhouse. Other alternatives are injecting colchicine into the secondary buds or applying colchicine-soaked cotton plugs to axillary buds.

  17. Simultaneous exposure to MRI-related static and low-frequency movement-induced time-varying magnetic fields affects neurocognitive performance : A double-blind randomized crossover study

    NARCIS (Netherlands)

    van Nierop, Lotte E; Slottje, Pauline; van Zandvoort, Martine; Kromhout, Hans

    2015-01-01

    PURPOSE: This experimental study aims to separate neurocognitive effects resulting from exposure to static magnetic stray fields (SMF) alone and the combination of SMF and low-frequency movement-induced time-varying magnetic fields (TVMF) using a 7 Tesla (T) MRI scanner in stand-by mode. METHODS: In

  18. 大功率高频接触焊双焊脚结构的改进与应用%Improvement and Application of High-power High-frequency Contact Welding Double Leg Structure

    Institute of Scientific and Technical Information of China (English)

    张新民; 王海峰; 储程国

    2016-01-01

    In order to solve the problems occurred in welding leg overlap joint during manufacture procedure of thick-wall and large diameter HFW pipe, such as strike a light and electrode burning loss, it analyzed the existing problems and influence of traditional contact welding leg structure, and found the important factors reducing electrode service life, including improper material selection, undersize, poor cooling, abnormal scratch, natural wear and so on. Through analysis on main reasons, it introduced a kind of double welding leg design scheme, and expounded its working theory and using method. Through practical application, it found this double welding leg design can effectively solve such problems.%为了解决大壁厚、中大直径HFW钢管在生产过程中焊脚电极搭接处出现的“打火”及电极烧损现象,分析了传统接触焊焊脚结构存在的问题以及影响,发现材料选择不当、尺寸过小、安装不当、冷却不良、异常刮擦和自然磨损等是降低电极使用寿命的重要因素。通过对主要原因进行分析,介绍了一种双焊脚的设计方案,并对其原理、使用方法进行了论述。通过在实际生产中进行应用,发现该双焊脚设计能够有效解决此类问题。

  19. Frequency standards

    CERN Document Server

    Riehle, Fritz

    2006-01-01

    Of all measurement units, frequency is the one that may be determined with the highest degree of accuracy. It equally allows precise measurements of other physical and technical quantities, whenever they can be measured in terms of frequency.This volume covers the central methods and techniques relevant for frequency standards developed in physics, electronics, quantum electronics, and statistics. After a review of the basic principles, the book looks at the realisation of commonly used components. It then continues with the description and characterisation of important frequency standards

  20. The double identity of linguistic doubling.

    Science.gov (United States)

    Berent, Iris; Bat-El, Outi; Brentari, Diane; Dupuis, Amanda; Vaknin-Nusbaum, Vered

    2016-11-29

    Does knowledge of language consist of abstract principles, or is it fully embodied in the sensorimotor system? To address this question, we investigate the double identity of doubling (e.g., slaflaf, or generally, XX; where X stands for a phonological constituent). Across languages, doubling is known to elicit conflicting preferences at different levels of linguistic analysis (phonology vs. morphology). Here, we show that these preferences are active in the brains of individual speakers, and they are demonstrably distinct from sensorimotor pressures. We first demonstrate that doubling in novel English words elicits divergent percepts: Viewed as meaningless (phonological) forms, doubling is disliked (e.g., slaflaf linguistic preferences doubly dissociate from sensorimotor demands: A single stimulus can elicit diverse percepts, yet these percepts are invariant across stimulus modality--for speech and signs. These conclusions are in line with the possibility that some linguistic principles are abstract, and they apply broadly across language modality.

  1. The role of Octopus 101 perimetry with diabetes program in the diagnosis of retinopathy in impaired glucose tolerance subjects%OCTOPUS视野计检查在糖耐量减低人群视网膜病变诊断中的应用价值

    Institute of Scientific and Technical Information of China (English)

    刘新琼; 夏米西努·吾斯曼; 何丽; 蒋升

    2012-01-01

    目的 应用Octopus101视野计的Diabetes程序,对无眼底可见DR的IGT人群进行视野检查,了解其视功能状况. 方法 对35例(70眼)IGT患者及年龄、性别相匹配的32名(64眼)血糖正常者,应用Octopus101视野计的Diabetes程序,行中心30°视野检查,以视野平均缺损(MD)为分析指标进行统计学检验. 结果 IGT组及对照组MD经t检验,有统计学意义(P<0.05). 结论 在眼底尚未出现可见的病理改变时,IGT患者中心30°的视野损害已经出现,并可由Octopus101视野计的Diabetes程序检测出.%Objective To investigate the role of Octopus 101 perimetry with diabetes program in the detection of early retinopathy in subjects with IGT. Methods Automated static perimetry within the central 30 degrees visual field (VF) was conducted with the Octopus 101 using diabetes program in 35 subjects(70 eyes) with IGT and 32 (64 eyes ) age- and sex-matched healthy subjects. The mean defects (MD) of VF were analyzed. Results The MDs were significantly highier in subjects with IGT than in controls (1. 778±1. 337 vs 1. 022±l. 105, P<0. 05). Conclusion The visual field defects have occurred in subjects with IGT and even without visible retinal vasculopathy, howerver, it could be detected by Octopus 101 perimetry with the central 30 degrees visual field using diabetes program.

  2. Frequency synthesiser

    NARCIS (Netherlands)

    Drago, Salvatore; Sebastiano, Fabio; Leenaerts, Dominicus Martinus Wilhelmus; Breems, Lucien Johannes; Nauta, Bram

    2016-01-01

    A low power frequency synthesiser circuit (30) for a radio transceiver, the synthesiser circuit comprising: a digital controlled oscillator configured to generate an output signal having a frequency controlled by an input digital control word (DCW); a feedback loop connected between an output and an

  3. Assessment of the effectiveness of low-level laser therapy on the hands of patients with rheumatoid arthritis: a randomized double-blind controlled trial.

    Science.gov (United States)

    Meireles, Sandra Mara; Jones, Anamaria; Jennings, Fabio; Suda, Alina Lica; Parizotto, Nivaldo Antônio; Natour, Jamil

    2010-05-01

    Assess the effectiveness of low-level laser therapy on pain reduction and improvement in function in the hands of patients with rheumatoid arthritis. A randomized double-blind controlled trial was carried out on 82 patients with rheumatoid arthritis. The experimental group was submitted to the application of laser therapy, whereas the control group received a placebo laser. Aluminum gallium arsenide laser was used, at a wavelength of 785 nm, dose of 3 J/cm(2) and mean power of 70 mW. The groups were homogenous at the beginning of the study with regard to the main variables (p > 0.05). There were no statistically significant differences between groups in most of the measurements taken at the end of the intervention including the primary variables; the following variables were the exceptions: favoring the experimental group-inflammation of the interphalangeal joint of the right thumb (p = 0.012) and perimetry of the interphalangeal joint of the left thumb (p = 0.013); and favoring the control group-flexion of the proximal interphalangeal joint of the right fifth finger (p = 0.021), perimetry of the third proximal interphalangeal joint of the right hand (p = 0.044), grip strength in the left hand (p = 0.010), and the work domain of the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire (p = 0.010). We conclude that low-level aluminum gallium arsenide laser therapy is not effective at the wavelength, dosage, and power studied for the treatment of hands among patients with rheumatoid arthritis.

  4. The Cambridge Double Star Atlas

    Science.gov (United States)

    MacEvoy, Bruce; Tirion, Wil

    2015-12-01

    Preface; What are double stars?; The binary orbit; Double star dynamics; Stellar mass and the binary life cycle; The double star population; Detecting double stars; Double star catalogs; Telescope optics; Preparing to observe; Helpful accessories; Viewing challenges; Next steps; Appendices: target list; Useful formulas; Double star orbits; Double star catalogs; The Greek alphabet.

  5. Double outlet right ventricle

    Science.gov (United States)

    ... medlineplus.gov/ency/article/007328.htm Double outlet right ventricle To use the sharing features on this page, please enable JavaScript. Double outlet right ventricle (DORV) is a heart disease that is ...

  6. Chromosome doubling method

    Science.gov (United States)

    Kato, Akio

    2006-11-14

    The invention provides methods for chromosome doubling in plants. The technique overcomes the low yields of doubled progeny associated with the use of prior techniques for doubling chromosomes in plants such as grasses. The technique can be used in large scale applications and has been demonstrated to be highly effective in maize. Following treatment in accordance with the invention, plants remain amenable to self fertilization, thereby allowing the efficient isolation of doubled progeny plants.

  7. Method on double-pass acousto-optic frequency shifter in absolute distance measurement using Fabry-P~rot interferometry%法-珀干涉绝对距离测量中的声光移频器双通道配置方法

    Institute of Scientific and Technical Information of China (English)

    张丽琼; 冬若; 朱敏昊; 张继涛

    2012-01-01

    为在能量天平动圈位移测量中实现大范围纳米精度法.珀干涉绝对距离测量,提出了声光移频器双通道配置,实现了调谐范围为200MHz的可调谐频差.通过分析声光移频器调制带宽与衍射效率的平衡与入射光束聚焦透镜的关系,确定透镜的最佳焦距范围;利用零级光斑分布特点准确定位入射光束,保证一级衍射光束质量.声光移频器在调制带宽内的实验单通道和双通道峰值衍射效率分别为79.54%,61.41%;声光移频器双通道配置输出的一级衍射光束与入射本征光束的拍频范围为440—640MHz,是单通道调制带宽输出220—320MHz的两倍,信噪比好.理论分析表明,声光移频器双通道配置方法实现的可调谐频差可测量腔长变化范围约为53mm的折叠法一珀腔.%In order to realize nanometer-scale absolute distance measurements based on Fabry-P6rot interferometry for long-range displace- ment measurement of the moving coil in Joule balance, the acousto-optic frequency shifter (AOFS) in double-pass configuration is presented, and a tunable frequency difference in a range of 200 MHz is achieved. The focus length of the lens is determined by ana- lyzing the relationship of the tradeoff between the AOFS modulation bandwidth and its diffraction efficiencies; the beam spot of the first-order diffraction beam is guaranteed by accurately positioning the focused beam according to the distribution of the zero-order diffraction beam spot. The experimental single-pass and double-pass peak diffraction efficiency of the AOFS are 79.54% and 61.41%, respectively; the tunable frequency difference of 440--4540 MHz, which is twice the single-pass modulation bandwidth output of 220---320 MHz, is obtained by the beat note between the incident beam and the first-order diffraction beam of the double-pass AOFS, and has a good signal-to-noise ratio. Theoretical analysis shows that a folded Fabry-P6rot

  8. 蓝-黄视野计与标准的白-白视野计对早期原发性开角型青光眼视野的对比研究%A study of comparing visual field loss in early primary open angle glaucoma detected by blue-on-yellow perimetry (B/Y) and white-on-white perimetry(W/W)

    Institute of Scientific and Technical Information of China (English)

    尹丽; 张德秀

    2004-01-01

    目的评价蓝-黄视野计(blue-on-yellow perimetry,B/Y)又称短波长视野计(short-wavelength automated perimetry,SWAP)与标准的白色视野计(white-on-white perimetry,W/W)在早期青光眼视野损害诊断中的意义.方法利用Humphrey-Ⅱ-750型全自动视野计C-30-2全阈值检测程序对20例(40只眼)正常人、20例(36只眼)可疑青光眼、18例(32只眼)确诊的早期原发性开角型青光眼(primary open-angle glaucoma,POAG)分别进行W/W与B/Y的视野检查.结果正常人、可疑青光眼、早期青光眼B/Y检测的全视网膜光敏感度均值(MS)低于W/W检测的结果,两者有显著性意义(t=11.68,P<0.01;t=14.01,P<0.01;t=14.68,P<0.01).B/Y检测光敏感度缺损均值(MD)与W/W检测的结果,正常人组无显著性意义(t=1.04,P<0.01),其它两组有显著性意义(t=4.88,P<0.01;t=3.378,P<0.01).W/W检查正常人组与可疑性青光眼的MS差别无显著意义(t=2.54,P>0.01),B/Y有显著意义(t=5.57,P<0.01).两组的MD差别均有显著意义(t=3.16,P<0.01,t=6.26,P<0.01);W/W与B/Y检查正常人组与早期青光眼组的MS差别有显著意义(t=6.47,P<0.0;t=10.19,P<0.01),两组的MD差别也有显著意义(t=4.34,P<0.01;t=6.77,P<0.01);可疑青光眼组与早期青光眼组MS差别有显著意义(t=4.19,P<0.01;t=3.57,P<0.01),两组的MD差别无显著意义(t=2.23,P>0.01;t=0.77,P>0.01).可疑青光眼组与早期青光眼组B/Y检测的视野相对缺损点总数比W/W检测的视野相对缺损点总数多,两者差别有显著意义(X2=28.6,P<0.01;X2=28.74,P<0.01)).W/W视野检查法与B/Y视野检查法检测青光眼视野损害的符合率为100%,而B/Y视野检查检查法的敏感性为62.5%.两种视野检查法检测早期青光眼视野缺损的阳性率,B/Y检测的异常阳性率90.6%(29/32),W/W检测的异常阳性率为75%(24/32),两者差异有显著性意义(u=2.97,P<0.01).结论B/Y检查法与W/W检查法在早期青光眼视野检查中具有一致

  9. Comparative Analysis of Guided Modal Properties of Double-Positive and Double-Negative Metamaterial Slab Waveguides

    Directory of Open Access Journals (Sweden)

    K. Y. Kim

    2009-06-01

    Full Text Available The guided modal properties of double-positive and double-negative metamaterial slab waveguides are numerically analyzed and compared when varying the dielectric and magnetic constants. As the cutoff frequencies of both slab waveguides remained unchanged when the absolute value of the refractive index was kept invariant, this enabled an effective comparison of the respective guided modes. Thus, the guided mode dispersion characteristics of the double-positive and double-negative slab waveguides were analyzed and compared, including several higher order modes. As a result, this comparative analysis provides greater physical insights and a better understanding of the guided modal characteristics of double-negative metamaterial slab waveguides.

  10. Low frequency (1-Hz), right prefrontal repetitive transcranial magnetic stimulation (rTMS) compared with venlafaxine ER in the treatment of resistant depression: a double-blind, single-centre, randomized study.

    Science.gov (United States)

    Bares, Martin; Kopecek, Miloslav; Novak, Tomas; Stopkova, Pavla; Sos, Peter; Kozeny, Jiri; Brunovsky, Martin; Höschl, Cyril

    2009-11-01

    Previous studies have shown effectiveness of repetitive transcranial magnetic stimulation (rTMS) in the treatment of depression. This double-blind study compared efficacy of l Hz rTMS over the right prefrontal dorsolateral cortex with venlafaxine ER in the treatment of resistant depression. A total of 60 inpatients with depressive disorder (DSM-IV criteria), who previously did not respond to at least one antidepressant treatment, were randomly assigned to 1 Hz rTMS with placebo and venlafaxine ER with sham rTMS for 4 weeks. The primary outcome measure was score change in the Montgomery-Asberg Depression Rating Scale (MADRS). We also used Clinical Global Impression (CGI) and Beck Depressive. Inventory-Short Form (BDI-SF). The response was defined as a >or=50% reduction of MADRS score. There were no significant differences between treatment groups in MADRS (p=0.38), BDI-SF (p=0.56) and CGI (p=0.17) scores from baseline to endpoint. Response rates for rTMS (33%) and venlafaxine (39%) as well as remission (MADRS score

  11. 基于双频伪距组合评估北斗广播电离层精度%Precision Assessment of Broadcast Ionospheric Model of BDS Based on Double-frequency Pseudo-range Combination

    Institute of Scientific and Technical Information of China (English)

    程娜; 贾小林

    2015-01-01

    Ionospheric delay is one major factor which affecting GNSS positioning,navigation,timing (PNT).In order to meet the needs of single-frequency users,the BDS provides the Klobuchar 8-parameters correction model in geographic coordi-nate system for ionospheric delay.In the monitoring and evaluation system,there are usually two methods to assess the broad-cast Ionospheric model,1)assessment by IGS precise ionospheric;2)assessment by dual-frequency pseudo-orange combina-tion.In this paper,the second method is used to assess the BDS’s broadcast ionosphericmodel.The results show that RMS and STD of broadcast ionospheric model are in 1.0 m,the relative precision is usually about 50%.%电离层时延误差是影响全球卫星导航系统定位、导航、授时精度的主要因素之一,为了满足单频用户的需求,我国北斗系统采用 Klobuchar 8参数模型进行电离层时延改正。在监测评估体系中,采用两种方法对电离层预报精度进行评估,1)全球卫星导航系统国际服务协会精密电离层模型评估;2)双频伪距组合评估。基于第二种方法对北斗系统的Klobuchar 模型进行了评估。评估结果显示,北斗系统广播电离层模型绝对精度包括均方根及标准差都在1.0 m 以内;相对精度 PER 一般为50%左右。

  12. Period-Doubling in 10 GHz Gain-Switched DFB Laser Diode

    Institute of Scientific and Technical Information of China (English)

    WU Jian; QIU Ji-Fang; LIN Jin-Tong

    2007-01-01

    The distinct period doubling behaviour in a 10 GHz gain-switched (GS) DFB laser is experimentally investigatedin frequency domain and in time domain. The period doubling occurs as the frequency of the rf driving signal is close to or higher than the -3 dB cutoff frequency of the DFB laser diode, and the amplitude of the rf driving signal required to achieve period doubling increases linearly with the increasing bias current of the laser diode.

  13. High power double-scale pulses from a gain-guided double-clad fiber laser

    Science.gov (United States)

    Zhang, Haitao; Gao, Gan; Li, Qinghua; Gong, Mali

    2017-03-01

    Generation of high power double-scale pulses from a gain-guided double-clad fiber laser is experimentally demonstrated. By employing the Yb-doped 10/130 double-clad fiber as the gain medium, the laser realizes an output power of 5.1 W and pulse energy of 0.175 µJ at repetition rate of 29.14 MHz. To the best of our knowledge, this average output power is the highest among the reported double-scale pulse oscillators. The autocorrelation trace of pulses contains the short (98 fs) and long (29.5 ps) components, and the spectral bandwidth of the pulse is 27.3 nm. Such double-scale pulses are well suited for seeding the high power MOPA (master oscillator power amplifier) systems, nonlinear frequency conversion and optical coherence tomography.

  14. Unintegrated double parton distributions

    CERN Document Server

    Golec-Biernat, K

    2016-01-01

    We present the construction of unintegrated double parton distribution functions which include dependence on transverse momenta of partons. We extend the formulation which was used to obtain the single unintegrated parton distributions from the standard, integrated parton distribution functions. Starting from the homogeneous part of the evolution equations for the integrated double parton distributions, we construct the unintegrated double parton distributions as the convolutions of the integrated double distributions and the splitting functions, multiplied by the Sudakov form factors. We show that there exist three domains of external hard scales which require three distinct forms of the unintegrated double distributions. The additional transverse momentum dependence which arises through the Sudakov form factors leads to non-trivial correlations in the parton momenta. We also discuss the non-homogeneous contribution to the unintegrated double parton distributions, which arises due to the splitting of a singl...

  15. On Double Vector Bundles

    Institute of Scientific and Technical Information of China (English)

    Zhuo CHEN; Zhang Ju LIU; Yun He SHENG

    2014-01-01

    In this paper, we construct a category of short exact sequences of vector bundles and prove that it is equivalent to the category of double vector bundles. Moreover, operations on double vector bundles can be transferred to operations on the corresponding short exact sequences. In particular, we study the duality theory of double vector bundles in term of the corresponding short exact sequences. Examples including the jet bundle and the Atiyah algebroid are discussed.

  16. On Double Vector Bundles

    OpenAIRE

    Chen, Zhuo; Liu, Zhangju; Sheng, Yunhe

    2011-01-01

    In this paper, we construct a category of short exact sequences of vector bundles and prove that it is equivalent to the category of double vector bundles. Moreover, operations on double vector bundles can be transferred to operations on the corresponding short exact sequences. In particular, we study the duality theory of double vector bundles in term of the corresponding short exact sequences. Examples including the jet bundle and the Atiyah algebroid are discussed.

  17. UNILATERAL INCOMPLETE DOUBLE URETER

    Directory of Open Access Journals (Sweden)

    Kaini

    2013-04-01

    Full Text Available ABSTRACT: Double ureter is a result of premature division of t he ureteric bud. The ureters may join in the lower third of their course and open thr ough a common orifice into the bladder. If they open independently into the bladder, the ureter draining the upper pelvis opens into the bladder below the opening of the other ureter. Patie nts with double ureter or double pelvis are more likely to develop urinary infection and calculi .

  18. Observing Double Stars

    Science.gov (United States)

    Genet, Russell M.; Fulton, B. J.; Bianco, Federica B.; Martinez, John; Baxter, John; Brewer, Mark; Carro, Joseph; Collins, Sarah; Estrada, Chris; Johnson, Jolyon; Salam, Akash; Wallen, Vera; Warren, Naomi; Smith, Thomas C.; Armstrong, James D.; McGaughey, Steve; Pye, John; Mohanan, Kakkala; Church, Rebecca

    2012-05-01

    Double stars have been systematically observed since William Herschel initiated his program in 1779. In 1803 he reported that, to his surprise, many of the systems he had been observing for a quarter century were gravitationally bound binary stars. In 1830 the first binary orbital solution was obtained, leading eventually to the determination of stellar masses. Double star observations have been a prolific field, with observations and discoveries - often made by students and amateurs - routinely published in a number of specialized journals such as the Journal of Double Star Observations. All published double star observations from Herschel's to the present have been incorporated in the Washington Double Star Catalog. In addition to reviewing the history of visual double stars, we discuss four observational technologies and illustrate these with our own observational results from both California and Hawaii on telescopes ranging from small SCTs to the 2-meter Faulkes Telescope North on Haleakala. Two of these technologies are visual observations aimed primarily at published "hands-on" student science education, and CCD observations of both bright and very faint doubles. The other two are recent technologies that have launched a double star renaissance. These are lucky imaging and speckle interferometry, both of which can use electron-multiplying CCD cameras to allow short (30 ms or less) exposures that are read out at high speed with very low noise. Analysis of thousands of high speed exposures allows normal seeing limitations to be overcome so very close doubles can be accurately measured.

  19. Research and Application of Realizing Thyristor Trigger Using “Double Narrow Pulse” by the Microcomputer Control High-frequency Pulse Column%微机控制高频脉冲列实现晶闸管“双窄脉冲触发”的研究与应用

    Institute of Scientific and Technical Information of China (English)

    刘觉民; 付义; 向增; 秦攀; 祖映翔

    2011-01-01

    运用冲量定理深入分析了高频脉冲列触发晶闸管的机理;通过建立励磁回路和晶闸管触发回路数学模型,由晶闸管开通时间、擎住电流、励磁回路与触发回路模型参数等数据,计算出感性负载下晶闸管触发的最小脉冲宽度和高频脉冲列周期与脉宽,据此设计出微机控制高频脉冲列晶闸管“双窄脉冲触发”程序.样机试验表明,晶闸管三相可控整流桥各路高频脉冲列和励磁电压波形稳定、对称性好,晶闸管触发精度高,达到励磁装置设计要求.%By using impulse theorem, we have analyzed the mechanism of trigger thyristor by high-frequency pulse instead of width pulse . Through the establishment of an excitation circuit and a trigger thyristor circuit mathematical model and with the thyristor switch time, latching current, perceptual load and pulse transformer model parameters, we have calculated the thyristor conduction of minimum pulse width, cycle and pulse-width of equivalent high-frequency pulse column. Accordingly, we have designed thyristor "double narrow pulse triggering" program based on microcomputer control high-frequency pulse column. A prototype test waveforms and data of trigger microcomputer excitation system have shown that high-frequency pulse column and the excitation voltage waveform of three-phase controlled thyristor rectifier bridge rostrum are stable and have good symmetry. Also, the excitation voltage is stable and continuously adjustable. It has satisfied the requirements of wide pulse triggering.

  20. Double beta decay experiments

    CERN Document Server

    Barabash, A S

    2011-01-01

    The present status of double beta decay experiments is reviewed. The results of the most sensitive experiments are discussed. Proposals for future double beta decay experiments with a sensitivity to the $$ at the level of (0.01--0.1) eV are considered.

  1. Dual doubled geometry

    NARCIS (Netherlands)

    Bergshoeff, Eric A.; Riccioni, Fabio; Alvarez-Gaumé, L.

    2011-01-01

    We probe doubled geometry with dual fundamental branes. i.e. solitons. Restricting ourselves first to solitonic branes with more than two transverse directions we find that the doubled geometry requires an effective wrapping rule for the solitonic branes which is dual to the wrapping rule for fundam

  2. An acoustic double fishnet using Helmholtz resonators.

    Science.gov (United States)

    Murray, A R J; Summers, I R; Sambles, J R; Hibbins, A P

    2014-09-01

    The acoustic transmission of a closely spaced pair of patterned and perforated rigid plates is explored in air. The structure resembles an acoustic double fishnet design, with each plate modified such that the gap between them acts as an array of Helmholtz resonators. This allows the center frequency of the stop band to be reduced by a factor greater than 2 from the value obtained for the conventional acoustic double fishnet design. Experimental results accord well with the predictions of a finite element model.

  3. A dual-loss-modulated intra-cavity frequency-doubled Q-switched and mode-locked Nd:Lu0.15Y0.85VO4/KTP green laser with a single-walled carbon nanotube saturable absorber and an acousto-optic modulator

    Science.gov (United States)

    Zhang, Gang; Zhao, Shengzhi; Yang, Kejian; Li, Guiqiu; Li, Dechun; Cheng, Kang; Han, Chao; Zhao, Bin; Wang, Yonggang

    2011-09-01

    By using both a single-walled carbon nanotube saturable absorber (SWCNT-SA) and an acousto-optic (AO) modulator, a dual-loss-modulated intra-cavity frequency-doubled Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4/KTP (KTiOPO4) green laser was demonstrated for the first time. The QML green laser characteristics such as the pulse width and single-pulse energy have been measured for different modulation frequencies of the AO modulator (fp). In particular, in comparison with the solely passively QML green laser with an SWCNT-SA, the dual-loss-modulated QML green laser can generate a more stable pulse train, a shorter pulse width of the Q-switched envelope, a greater pulse energy and a higher average peak power. For the dual-loss-modulated QML green laser, at a pump power of 7.9 W and a repetition rate of 10 kHz, the pulse width and the pulse energy of the Q-switch envelope and the average peak power of the QML green laser are 50 ns, 20.34 µJ and 15.5 kW, respectively, corresponding to a pulse width compression of 77%, a pulse energy improvement factor of six times and a QML peak power increase factor of 16 times when compared with those for the solely passively QML green laser. The experimental results show that the dual-loss modulation is an efficient method for the generation of a stable QML green laser with an SWCNT-SA.

  4. Topological Quantum Double

    Science.gov (United States)

    Bonneau, Philippe

    Following a preceding paper showing how the introduction of a t.v.s. topology on quantum groups led to a remarkable unification and rigidification of the different definitions, we adapt here, in the same way, the definition of quantum double. This topological double is dualizable and reflexive (even for infinite dimensional algebras). In a simple case we show, considering the double as the "zero class" of an extension theory, the uniqueness of the double structure as a quasi-Hopf algebra. A la suite d'un précédent article montrant comment l'introduction d'une topologie d'e.v.t. sur les groupes quantiques permet une unification et une rigidification remarquables des différentes définitions, on adapte ici de la même manière la définition du double quantique. Ce double topologique est alors dualisable et reflexif (même pour des algèbres de dimension infinie). Dans un cas simple on montre, en considérant le double comme la "classe zéro" d'une théorie d'extensions, l'unicité de cette structure comme algèbre quasi-Hopf.

  5. BBO晶体腔内位置对灯泵Cr:LiSAF激光器腔内倍频的影响的研究%The Research of the Location Effecting of BBO Crystal on the Output Energy of an Intracavity Frequency-doubled Flashlamp-pumped Cr:LiSAF Laser

    Institute of Scientific and Technical Information of China (English)

    陈长水; 赵柯; 王佩琳; 谢建平

    2000-01-01

    本文实验研究了由于色散引起的BBO晶体腔内位置对灯泵Cr:LiSAF激光器腔内倍频输出的影响,并从理论上获得了腔内倍频的BBO晶体的最佳位置为基波与谐波的位相差2π的整数倍,同时,考虑到容许的基波与谐波的位相差为±π/4时,对应基波和谐波波长分别为:900nm和450 nm处,腔内倍频的BBO晶体的位置调整范围为9.4 mm.%The location of BBO crystal in the cavity effecting the output energy in the intracavity frequency-doubling of a flashlamp-pumped Cr:LiSAF laser is researched.The benefit net phase shift due to dispersion between the fundamental and the harmonic wave beam in the air path between BBO crystal and the mirror M3 is a multiple of 2π. If the net phase shift ofπ/4 is allowed, this requires a BBO crystal movement of no more than 9.4 mm at the fundamental wave of 900 nm and the harmonic wave of 450 nm.

  6. Study on "double dawn

    Institute of Scientific and Technical Information of China (English)

    刘次沅; 李建科; 周晓陆

    1999-01-01

    The ancient record, "During the first year of King Yi, the day dawned twice at Zheng", has provided important clues to early Chinese chronicles. The astronomical conditions and visible area distributions related to such a "double dawn" event are discussed, and the precision and current problems in the calculations of ancient astronomical phenomena are shown. On such a basis, all the solar eclipses from 1000 BC to 840 BC are calculated and their associated "double dawn" features investigated. The conclusion that the "double dawn" was a solar eclipse occurring on April 21st, 899 BC is corfirmed to be the most reasonable.

  7. Synthesis, structure, and frequency-doubling effect of calcium cyanurate.

    Science.gov (United States)

    Kalmutzki, Markus; Ströbele, Markus; Wackenhut, Frank; Meixner, Alfred J; Meyer, H-Jürgen

    2014-12-15

    Calcium cyanurate is synthesized by reacting calcium chloride with potassium cyanate following a solid-state reaction. The formation of the new compound Ca3(O3C3N3)2 (CCY), which occurs by the cyclotrimerization of cyanate ions, was examined thermoanalytically and the crystal structure was determined by single-crystal structure analysis. The structure of CCY is closely related to the structure of the well-known oxoborate β-BaB2O4 (BBO). Second harmonic generation (SHG) measurements on crystal powders show a higher SHG efficiency for CCY than for BBO by about one order of magnitude. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Hermetic optical-fiber iodine frequency standard.

    Science.gov (United States)

    Light, Philip S; Anstie, James D; Benabid, Fetah; Luiten, Andre N

    2015-06-15

    We have built an optical-frequency standard based on interrogating iodine vapor that has been trapped within the hollow core of a hermetically sealed kagome-lattice photonic crystal fiber. A frequency-doubled Nd:YAG laser locked to a hyperfine component of the P(142)37-0 I2127 transition using modulation transfer spectroscopy shows a frequency stability of 3×10(-11) at 100 s. We discuss the impediments in integrating this all-fiber standard into a fully optical-fiber-based system, and suggest approaches that could improve performance of the frequency standard substantially.

  9. Neutrinoless double beta decay

    Indian Academy of Sciences (India)

    Kai Zuber

    2012-10-01

    The physics potential of neutrinoless double beta decay is discussed. Furthermore, experimental considerations as well as the current status of experiments are presented. Finally, an outlook towards the future, work on nuclear matrix elements and alternative processes is given.

  10. Double conjoining vas deferens.

    Science.gov (United States)

    Gravesen, R G

    1980-03-01

    The importance of careful palpation of the scrotal contents and follow-up semen analysis when performing vasectomies is proved by this case report of a double vas deferens conjoining into a single vas.

  11. Double balloon enteroscopy examinations in general anesthesia

    Institute of Scientific and Technical Information of China (English)

    Laszlo; Zubek; Lena; Szabo; Peter; Laszlo; Lakatos; Janos; Papp; Janos; Gal; Gabor; Elo

    2010-01-01

    AIM:To demonstrate that the double balloon enteroscopy(DBE) can be safely performed in general anesthesia with intubation.METHODS:We performed a retrospective examination between August 2005 and November 2008 amongpatients receiving intubation narcosis due to DBE examination.The patients were grouped based on sex,age and physical status.Anesthesia records includedduration of anesthesia,quantity of medication usedand anesthesia-related complications.We determinedthe frequency of complications in the differen...

  12. 基于频率选择表面的双层改进型互补结构太赫兹带通滤波器研究%Terahertz bandpass filter using double-layer reformative complementary frequency selective surface structures

    Institute of Scientific and Technical Information of China (English)

    兰峰; 高喜; 亓丽梅

    2014-01-01

    The simulation and experimental study of a bandpass frequency selective surface filter in terahertz (THz) range using double-layer modified complementary structures are conducted in this paper. The modified four-split comple-mentary electric inductive capacitive (CELC) structure is introduced as the resonant cell of the filter. The primary design objective is to improve the filtering performances of double-layer complementary metamaterial structures built on intensified thickening quartz substrate. The bandpass filter centered at 0.28 THz is simulated, fabricated and mea-sured. Experimental results from 0.1 to 0.6 THz measured by THz time-domain spectroscopy are in excellent agreement with simulation. The reformative CELC bandpass filter has the advantages of a low cost, low loss, steepness of skirts, out-of-band rejection, and etalon resonance rejection.%通过仿真计算和实验研究了一种基于频率选择表面的双层改进型互补结构太赫兹带通滤波器.对四裂缝互补型电感电容式谐振单元结构进行了改进,可以在提高滤波性能的同时增加单晶石英介质衬底的厚度.利用电磁仿真技术设计并加工了中心频率为0.28 THz的带通滤波器,并利用太赫兹时域光谱仪测试了在0.1—0.6 THz范围内此滤波器的传输频谱特性,实验结果与仿真结果基本一致.结果表明,利用双层改进型互补结构可以设计出对于入射角度不敏感、带外抑制佳、边带陡峭度大、能有效抑制寄生谐振的宽带太赫兹带通滤波器,并降低了加工难度.

  13. A Radio Frequency Charge Parity Meter

    OpenAIRE

    Schroer, M. D.; Jung, M.; Petersson, K. D.; Petta, J. R.

    2012-01-01

    We demonstrate a total charge parity measurement by detecting the radio frequency signal that is reflected by a lumped element resonator coupled to a single InAs nanowire double quantum dot. The high frequency response of the circuit is used to probe the effects of the Pauli exclusion principle at interdot charge transitions. Even parity charge transitions show a striking magnetic field dependence that is due to a singlet-triplet transition, while odd parity transitions are relatively insensi...

  14. Theory of Double Ladder Lumped Circuits With Degenerate Band Edge

    CERN Document Server

    Sloan, Jeff; Capolino, Filippo

    2016-01-01

    Conventional periodic LC ladder circuits exhibit a regular band edge between a pass and a stop band. Here for the first time we develop the theory of simple yet unconventional double ladder circuits exhibiting a special degeneracy condition referred to as degenerate band edge (DBE). This special DBE condition is associated with four independent eigenstates of the double ladder that coalesce into a single one when the operative frequency coincides with the DBE one. In particular, we show that double ladder resonators may exhibit giant loaded quality factor near the DBE and stable resonance frequency against load variations. These two properties in the proposed circuit are superior to the analogous properties in single ladder circuits. Our proposed analysis leads to analytic expressions for all circuit quantities thus providing insight into the very complex behavior near points of degeneracy in periodic circuits; and provides a design procedure for the use of such double ladder in practical applications. Intere...

  15. Project Half Double

    DEFF Research Database (Denmark)

    Ehlers, Michael; Adland, Karoline Thorp; Boston, Nicolai Elborough

    Project Half Double has a clear mission to succeed in finding a project methodology that can increase the success rate of our projects while increasing the speed at which we generate new ideas and develop new products and services. Chaos and complexity should be seen as a basic condition...... and as an opportunity rather than a threat and a risk. We are convinced that by doing so, we can strengthen Denmark’s competitiveness and play an important role in the battle for jobs and future welfare. The overall goal is to deliver “projects in half the time with double the impact”, where projects in half the time...... should be understood as half the time to impact (benefit realisation, effect is achieved) and not as half the time for project execution. The purpose of Project Half Double is to improve Danish industrial competitiveness by radically increasing the pace and impact of the development and innovation...

  16. Double-peak Splitting in High-order Harmonics Generation

    Institute of Scientific and Technical Information of China (English)

    WANG Yingsong; LIU Yaqing; YANG Xiaodong; XU Zhizhan

    2000-01-01

    When the intensity of the driving pulse is much higher than the saturation intensity of the media involved, the double-peak splitting in frequency domain emerges in the generated high-order harmonic spectra. The possible origins of this splitting are carefully investigated. The ionization of the gas media and the propagation effect of harmonic field are the main reason for the double-peak splitting observed.

  17. Double arch mirror study

    Science.gov (United States)

    Vukobratovich, D.; Hillman, D.

    1983-01-01

    The development of a method of mounting light weight glass mirrors for astronomical telescopes compatible with the goals of the Shuttle Infrared Telescope Facility (SIRTF) was investigated. A 20 in. diameter double arch lightweight mirror previously fabricated was modified to use a new mount configuration. This mount concept was developed and fabricated. The mounting concept of the double mounting mirror is outlined. The modifications made to the mirror, fabrication of the mirror mount, and room temperature testing of the mirror and mount and the extension of the mirror and mount concept to a full size (40 in. diameter) primary mirror for SIRTF are discussed.

  18. John Deakin: Double Exposures

    Directory of Open Access Journals (Sweden)

    Paul Rousseau

    2015-11-01

    Full Text Available In this series of short films made by Jonathan Law, the art historian James Boaden, and the curator of The John Deakin Archive, Paul Rousseau, discuss the double-exposure images made by the photographer John Deakin (1912-1972 in the 1950s and 1960s. The films ask you, firstly, to look closely at the images being discussed. Each one begins with a sustained and intense shot of a single image before opening up to a wide-ranging discussion about Deakin, double exposures, and photography.

  19. Double Beta Decay

    CERN Document Server

    Elliott, Steven R

    2011-01-01

    At least one neutrino has a mass of about 50 meV or larger. However, the absolute mass scale for the neutrino remains unknown. Furthermore, the critical question: Is the neutrino its own antiparticle? is unanswered. Studies of double beta decay offer hope for determining the absolute mass scale. In particular, zero-neutrino double beta decay (\\BBz) can address the issues of lepton number conservation, the particle-antiparticle nature of the neutrino, and its mass. A summary of the recent results in \\BBz, and the related technologies will be discussed in the context of the future \\BBz\\ program.

  20. Double-helix stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Moroz, P.E.

    1997-09-01

    A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A {approx} 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-{beta} MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications.

  1. Project Half Double

    DEFF Research Database (Denmark)

    Svejvig, Per; Gerstrøm, Anna; Frederiksen, Signe Hedeboe

    The Half Double mission: Project Half Double has a clear mission. We want to succeed in finding a project methodology that can increase the success rate of our projects while increasing the development speed of new products and services. We are convinced that by doing so we can strengthen...... projects and to document their development. The purpose of this addendum is thus to document the development in the pilot projects from June 2016 to January 2017 with particular focus on the impact they have created. This Addendum is a supplement and should be read in conjunction with the Phase 1 report...

  2. Reflection Positive Doubles

    CERN Document Server

    Jaffe, Arthur

    2016-01-01

    Here we introduce reflection positive doubles, a general framework for reflection positivity, covering a wide variety of systems in statistical physics and quantum field theory. These systems may be bosonic, fermionic, or parafermionic in nature. Within the framework of reflection positive doubles, we give necessary and sufficient conditions for reflection positivity. We use a reflection-invariant cone to implement our construction. Our characterization allows for a direct interpretation in terms of coupling constants, making it easy to check in concrete situations. We illustrate our methods with numerous examples.

  3. A matterless double slit

    CERN Document Server

    King, B; Keitel, C H; 10.1038/nphoton.2009.261

    2013-01-01

    Double-slits provide incoming photons with a choice. Those that survive the passage have chosen from two possible paths which interfere to distribute them in a wave-like manner. Such wave-particle duality continues to be challenged and investigated in a broad range of disciplines with electrons, neutrons, helium atoms, C60 fullerenes, Bose-Einstein condensates and biological molecules. All variants have hitherto involved material constituents. We present a matterless double-slit scenario in which photons generated from virtual electron-positron pair annihilation in head-on collisions of a probe laser field with two ultra-intense laser beams form a double-slit interference pattern. Such electromagnetic fields are predicted to induce material-like behaviour in the vacuum, supporting elastic scattering between photons. Our double-slit scenario presents on the one hand a realisable method to observe photon-photon scattering, and demonstrates on the other, the possibility of both controlling light with light and n...

  4. The Double Nine Festival

    Institute of Scientific and Technical Information of China (English)

    1993-01-01

    THE Double Nine Festival,which falls on theninth day of the ninth lunar month,is anancient tradition among Han Chinese.TheBook of Changes,a famous classic in ancient China,designates the number 9 as yang(the masculine orpositive principle in nature).Thus Double Nine isknown as Chongyang in Chinese,meaning doubleyang.In The Western Capital Miscellancy,Ge Hong(281-341)of the Eastern Jin Dynasty described onetraditional custom of the Western Han Dynasty (206B.C.-A.D.24):″Wearing medicinal comel (Cornusofficinalis),eating double yang cake and drinking chry-santhemum wine on the ninth day of the ninth lunarmonth all help to prolong life.″Therefore the DoubleNine Festival is also celebrated as a festival for the old.People often wear medicinal cornel and climb to ahigh place to drink chrysanthemum wine.The customcomes from a legend:Huan Jing was a student ofnecromancer Fei Changfang in the Eastern Han Dy-nasty (25-220). One day Fei warned Huan that thelatter’s family was in danger of suffering a diaster ont

  5. Chaotic period doubling

    NARCIS (Netherlands)

    Chandramouli, V. V. M. S.; Martens, M.; De Melo, W.; Tresser, C. P.

    2009-01-01

    The period doubling renormalization operator was introduced by Feigenbaum and by Coullet and Tresser in the 1970s to study the asymptotic small-scale geometry of the attractor of one-dimensional systems that are at the transition from simple to chaotic dynamics. This geometry turns out not to depend

  6. Aristotle and Double Effect

    DEFF Research Database (Denmark)

    Di Nucci, Ezio

    2014-01-01

    There are some interesting similarities between Aristotle’s ‘mixed actions’ in Book III of the Nicomachean Ethics and the actions often thought to be justifiable with the Doctrine of Double Effect. Here I analyse these similarities by comparing Aristotle’s examples of mixed actions with standard ...

  7. Bichromatic field generation from double-four-wave mixing in a double-electromagnetically induced transparency system

    CERN Document Server

    Liu, Yang; Ding, Dongsheng; Shi, Baosen; Guo, Guangcan

    2012-01-01

    We demonstrate the double electromagnetically induced transparency (double-EIT) and double four-wave mixing (double-FWM) based on a new scheme of non-degenerate four-wave mixing (FWM) involving five levels of a cold 85Rb atomic ensemble, in which the double-EIT windows are used to transmit the probe field and enhance the third-order nonlinear susceptibility. The phase-matching conditions for both four-wave mixings could be satisfied simultaneously. The frequency of one component of the generated bichromatic field is less than the other by the ground-state hyperfine splitting (3GHz). This specially designed experimental scheme for simultaneously generating different nonlinear wave-mixing processes is expected to find applications in quantum information processing and cross phase modulation. Our results agree well with the theoretical simulation.

  8. Electrolyte-Gated Graphene Ambipolar Frequency Multipliers for Biochemical Sensing.

    Science.gov (United States)

    Fu, Wangyang; Feng, Lingyan; Mayer, Dirk; Panaitov, Gregory; Kireev, Dmitry; Offenhäusser, Andreas; Krause, Hans-Joachim

    2016-04-13

    In this Letter, the ambipolar properties of an electrolyte-gated graphene field-effect transistor (GFET) have been explored to fabricate frequency-doubling biochemical sensor devices. By biasing the ambipolar GFETs in a common-source configuration, an input sinusoidal voltage at frequency f applied to the electrolyte gate can be rectified to a sinusoidal wave at frequency 2f at the drain electrode. The extraordinary high carrier mobility of graphene and the strong electrolyte gate coupling provide the graphene ambipolar frequency doubler an unprecedented unity gain, as well as a detection limit of ∼4 pM for 11-mer single strand DNA molecules in 1 mM PBS buffer solution. Combined with an improved drift characteristics and an enhanced low-frequency 1/f noise performance by sampling at doubled frequency, this good detection limit suggests the graphene ambipolar frequency doubler a highly promising biochemical sensing platform.

  9. Intracavity doubling of CW Ti:sapphire laser to 392.5 nm using BiBO-crystal

    DEFF Research Database (Denmark)

    Mortensen, Jesper Liltorp; Thorhauge, Morten; Tidemand-Lichtenberg, Peter

    2005-01-01

    In this work we present results obtained for intra-cavity frequency-doubling of a 785 nm CW Ti:sapphire laser utilising BiBO as the non-linear crystal. Intracavity doubling offers several advantages compared to extra-cavity doubling, such as no need to couple to an external resonance cavity...

  10. 基于双二阶广义积分锁频环的光伏并网发电系统仿真研究%Simulation of PV grid-connected generation system based on double second-order generalized integral frequency-locked loop

    Institute of Scientific and Technical Information of China (English)

    张占锋; 樊艳芳; 王一波; 王环

    2016-01-01

    电网不对称故障时,光伏发电系统中的负序分量和谐波分量会影响并网逆变器中的锁相环及控制算法.文章提出一种具有自适应滤波的双二阶广义积分锁频环技术,用于电网电压和并网电流正负序分量的提取以及电网电压同步信号的检测,并将该技术引入到正负序双电流环控制策略,通过优化不平衡控制策略中锁相环的方法,提升光伏并网逆变器整个控制系统应对电网不对称故障的能力.通过Matlab/Simulink软件平台搭建基于DSOGI-FLL锁频环的光伏并网发电系统模型并进行了仿真研究,结果表明,文章控制策略在电网不对称故障时有助于消除有功功率的2倍频波动以及抑制并网电流中的谐波分量.%Negative sequence and harmonic components of PV power generation system had an important influence on phase locked-loop and control algorithm of grid-connected inverter under grid asymmetrical fault.Based on the above problems,in order to extract positive-negative sequence components of grid voltage and grid-connected current and detect the synchronization signal of grid voltage,this paper proposed a double second-order generalized integrator frequency-locked loop (DSOGI-FLL) technology with adaptive filtering.And the technology was introduced into the positive-negative sequence dual current control strategy.The method of optimizing phase-locked loop in unbalanced control strategy improved the whole control system's ability of PV grid-connected inverter to cope with gird asymmetric fault.The grid-connected PV power generation system based on DSOGI-FLL was simulated by using Matlab/Simulink software.The results showed thatThis method contributes to eliminate the 2 harmonic wave of active power and restrain the harmonic component of grid-connected current under grid asymmetrical fault.

  11. Phonon tunneling through a double barrier system

    Energy Technology Data Exchange (ETDEWEB)

    Villegas, Diosdado [Departamento de Física, Universidad Central “Marta Abreu” de Las Villas, CP 54830, Santa Clara, Villa Clara (Cuba); Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico); León-Pérez, Fernando de [Centro Universitario de la Defensa de Zaragoza, Ctra. de Huesca s/n, E-50090 Zaragoza (Spain); Pérez-Álvarez, R. [Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca (Mexico); Arriaga, J., E-mail: arriaga@ifuap.buap.mx [Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico)

    2015-04-15

    The tunneling of optical and acoustic phonons at normal incidence on a double-barrier is studied in this paper. Transmission coefficients and resonance conditions are derived theoretically under the assumption that the long-wavelength approximation is valid. It is shown that the behavior of the transmission coefficients for the symmetric double barrier has a Lorentzian form close to resonant frequencies and that Breit–Wigner's formula have a general validity in one-dimensional phonon tunneling. Authors also study the so-called generalized Hartman effect in the tunneling of long-wavelength phonons and show that this effect is a numerical artifact resulting from taking the opaque limit before exploring the variation with a finite barrier width. This study could be useful for the design of acoustic devices.

  12. Double negative metamaterials based on ferromagnetic microwires

    Science.gov (United States)

    Carbonell, Jorge; García-Miquel, Héctor; Sánchez-Dehesa, José

    2010-01-01

    Ferromagnetic microwires are investigated as fundamental components to generate metamaterials with double negative parameters. Electric and magnetic responses are, respectively, based on the finite conductivity and ferromagnetic resonance of the wires that in turn depend on their chemical composition. Tuning properties of samples are investigated in terms of the composition of the alloy and the applied magnetic field. The samples are measured and simulated in a waveguide environment for a large microwave frequency range. Numerical modeling supports the experimental results and helps to understand the physics involved in the transmission phenomena. Radius and conductivity of the wires are pointed out as the most critical parameters to generate a double negative response in terms of permittivity and permeability.

  13. Application of Octopus 101 automated perimetry with kinetic and static program in patients with the anterior ischemic optic neuropathy%Octopus 101型视野计在检测缺血性视神经病变中的观察

    Institute of Scientific and Technical Information of China (English)

    王韧琰; 钟勇; 董方田; 赵鹏; 施维; 宋德禄

    2010-01-01

    目的 评价Octopus 101型自动视野计动态和静态程序在检查前部缺血性视神经病变(MON)中各自的优缺点,探讨两种视野检查方法在AION疾病中的临床应用价值.方法 对2006年6月至2008年9月经北京协和医院门诊确诊的45例MON患者进行Octopus自动视野计动态视野检查和中心30°及周边60°静态自动视野的检查.分析比较患者静态程序中的平均缺陷度(MD)、丢失方差(LV)、动态程序中不同视标参数下等视线的面积及反应延迟时间(RT)及其与年龄的相关性等.结果 AION可出现各种与视神经相关的视野缺损,较常见的有鼻侧缺损(25%)、下半偏盲(20.83%)和盲点相连的下方束状缺损(20.83%),动态视野检查有不同程度的等视线内陷,Ⅲ-4e与Ⅰ-2e两种不同的视标对MON患者检出的等视线面积差异有统计学意义(P<0.01);Ⅰ-2e视标更多地发现了周边视野的缺损.结论 Octopus 101自动视野计可以在同一视野计上先后完成静态及动态视野的检查.临床上对于可能既累及中心30°,又累及周边视野的如AION等疾病,有必要联合动、静态视野检查法,以更准确地捕捉到30°视野范围内的暗点及周边视野的压陷,且能最大限度地发挥了检查视标标准化、检查结果量化的优势.%ObjectiveTo investigate the clinical significance of the Octopus 101 kinetic and Static combined automatic perimetry in Anterior Ischemic Optic Neuropathy (AION). To assess the merit and demerit of Octopus 101 kinetic and static combined automatic perimetry performed in AION cases. Methods 45 AION patients were detected with Octopus 101 with kinetic and static 30° ,60°scope static program from June 2006 to September 2008. The mean defect(MD) ,loss variance(LV), areas of isopter, and reaction time were analyzed. The correlation between MD,areas of isopter and reaction time were analyzed. Results In AION, there are kinds of visual field defect related to the

  14. Double-Skin Facade

    DEFF Research Database (Denmark)

    Kalyanova, Olena

    difficulties experienced by scientists when attempting to model DSF thermal and energy performance were examined. In addition, the lack of experimental studies and empirical validation of models was realized, many numerical models have not been empirically validated and most of them require an expert knowledge...... IEA Annex 34/43, subtask E "Double-Skin Facade". The results of empirical validation are discussed in this work. Discussion and analysis of experimental results is carried out. It has lead to hypothesis of recirculation flow phenomenon in the DSF cavity. Finally, a suggestion of a new numerical model......Double-Skin Facades (DSF) are gaining popularity that, in fact, appears to be independent from sturdy critics of the concept in the past years. DSF buildings are being built in Europe and worldwide, DSF concept is being taught at schools of architecture and fully glazed office buildings are being...

  15. Algebra of Majorana doubling.

    Science.gov (United States)

    Lee, Jaehoon; Wilczek, Frank

    2013-11-27

    Motivated by the problem of identifying Majorana mode operators at junctions, we analyze a basic algebraic structure leading to a doubled spectrum. For general (nonlinear) interactions the emergent mode creation operator is highly nonlinear in the original effective mode operators, and therefore also in the underlying electron creation and destruction operators. This phenomenon could open up new possibilities for controlled dynamical manipulation of the modes. We briefly compare and contrast related issues in the Pfaffian quantum Hall state.

  16. Double Cortex Syndrome

    OpenAIRE

    1999-01-01

    The incidence of mutations in the X-linked gene doublecortin in patients with “double cortex” syndrome (DC; also called subcortical band heterotopia or laminar heterotopia) and familial DC with lissencephaly was investigated in a cohort of 8 pedigrees and 47 sporadic patients with DC examined at the Division of Neurogenics, Beth Israel Deaconess Medical Center, Boston, and multiple centers in the US and abroad.

  17. Twisted quantum doubles

    Directory of Open Access Journals (Sweden)

    Daijiro Fukuda

    2004-01-01

    Full Text Available Using diagrammatic pictures of tensor contractions, we consider a Hopf algebra (Aop⊗ℛλA** twisted by an element ℛλ∈A*⊗Aop corresponding to a Hopf algebra morphism λ:A→A. We show that this Hopf algebra is quasitriangular with the universal R-matrix coming from ℛλ when λ2=idA, generalizing the quantum double construction which corresponds to the case λ=idA.

  18. Double-Glazing Interferometry

    OpenAIRE

    Toal, Vincent; Mihaylova, Emilia

    2009-01-01

    This note describes how white light interference fringes can be seen by observing the Moon through a double-glazed window. White light interferometric fringes are normally observed only in a well-aligned interferometer whose optical path difference is less than the coherence length of the light source, which is approximately one micrometer for white light. Obtaining such fringes in a Michelson interferometer is not a trivial task.1 The interferometer is typically illuminated with a monochroma...

  19. Active nuclear spin maser oscillation with double cell

    Directory of Open Access Journals (Sweden)

    Hikota E.

    2014-03-01

    Full Text Available Uncertainty in the frequency precision of the planned experiment to search for a 129Xe atomic electric dipole moment is dominated by drifts in the frequency shift due to contact interaction of 129Xe with polarized Rb valence electrons. In order to suppress the frequency shift, a double-cell geometry has been adopted for the confinement of 129Xe gas. A new process has been identified to take part in the optical detection of spin precession. The parameters controlling the oscillation of the maser in this new double-cell arrangement were optimized. As a result, the frequency shift has been reduced by a factor of 10 or more from the former single-cell geometry.

  20. Double pendulum contact problem

    Directory of Open Access Journals (Sweden)

    Špička J.

    2014-06-01

    Full Text Available The work concerns contact problems focused on biomechanical systems modelled by a multibody approach. The example is modelling of impact between a body and an infrastructure. The paper firstly presents algorithm for minimum distance calculation. An analytical approach using a tangential plain perpendicular to an initial one is applied. Contact force generated during impact is compared by three different continuous force models, namely the Hertz’s model, the spring-dashpot model and the non-linear damping model. In order to identify contact parameters of these particular models, the method of numerical optimization is used. Purpose of this method is to find the most corresponding results of numerical simulation to the original experiment. Numerical optimization principle is put upon a bouncing ball example for the purpose of evaluation of desirable contact force parameters. The contact modelling is applied to a double pendulum problem. The equation of motion of the double pendulum system is derived using Lagrange equation of the second kind with multipliers, respecting the contact phenomena. Applications in biomechanical research are hinted at arm gravity motion and a double pendulum impact example.

  1. What is Double Parton Scattering?

    CERN Document Server

    Manohar, Aneesh V

    2012-01-01

    Processes such as double Drell-Yan and same-sign WW production have contributions from double parton scattering, which are not well-defined because of a delta(z_\\perp=0) singularity that is generated by QCD evolution. We study the single and double parton contributions to these processes, and show how to handle the singularity using factorization and operator renormalization.

  2. Colloidal Double Quantum Dots.

    Science.gov (United States)

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon

  3. Frequency noise in frequency swept fiber laser

    DEFF Research Database (Denmark)

    Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2013-01-01

    This Letter presents a measurement of the spectral content of frequency shifted pulses generated by a lightwave synthesized frequency sweeper. We found that each pulse is shifted in frequency with very high accuracy. We also discovered that noise originating from light leaking through the acousto...

  4. Frequency noise in frequency swept fiber laser.

    Science.gov (United States)

    Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2013-04-01

    This Letter presents a measurement of the spectral content of frequency shifted pulses generated by a lightwave synthesized frequency sweeper. We found that each pulse is shifted in frequency with very high accuracy. We also discovered that noise originating from light leaking through the acousto- optical modulators and forward propagating Brillouin scattering appear in the spectrum.

  5. High-Frequency-Induced Cathodic Breakdown during Plasma Electrolytic Oxidation

    Science.gov (United States)

    Nominé, A.; Nominé, A. V.; Braithwaite, N. St. J.; Belmonte, T.; Henrion, G.

    2017-09-01

    The present communication shows the possibility of observing microdischarges under cathodic polarization during plasma electrolytic oxidation at high frequency. Cathodic microdischarges can ignite beyond a threshold frequency found close to 2 kHz. The presence (respectively, absence) of an electrical double layer is put forward to explain how the applied voltage can be screened, which therefore prevents (respectively, promotes) the ignition of a discharge. Interestingly, in the conditions of the present study, the electrical double layer requires between 175 and 260 μ s to form. This situates the expected threshold frequency between 1.92 and 2.86 kHz, which is in good agreement with the value obtained experimentally.

  6. Small Signal Circuit Model of Double Photodiodes

    Institute of Scientific and Technical Information of China (English)

    HAN Jian-zhong; Ni Guo-qiang; MAO Lu-hong

    2004-01-01

    The transmission delay of photogenerated carriers in a CMOS-process-compatible double photodiode (DPD) is analyzed by using device simulation. The DPD small signal equivalent circuit model which includes transmission delay of photogenerated carriers is given. From analysis on the frequency domain of the circuit model the device has two poles. One has the relationship with junction capacitance and the DPD's load,the other with the depth and the doping concentration of the N-well in the DPD. Different depth of the Nwell and different area of the DPDs with bandwidth were compared. The analysis results are important to design the high speed DPDs.

  7. Design of double negativity elastic metamaterial

    Directory of Open Access Journals (Sweden)

    Y.C. Su

    2015-01-01

    Full Text Available A metamaterial model that possesses simultaneously negative effective mass density and negative effective Young’s modulus is proposed in this study. Dispersion curves and dynamic responses of the model are investigated. In the double negative frequency region, it is demonstrated that the phase velocity is negative. In addition, it was found that the band gap region of the metamaterial can be predicted accurately by taking parts of single-unit cell to analyze the steady-state response. The design is also fabricated by a 3D printer.

  8. Chromosome doubling in vine cacti hybrids.

    Science.gov (United States)

    Tel-Zur, N; Abbo, S; Bar-Zvi, D; Mizrahi, Y

    2003-01-01

    We performed reciprocal crosses between the tetraploid Selenicereus megalanthus and the diploid Hylocereus species, H. undatus and H. polyrhizus. S. megalanthus x H. undatus gave rise to viable hexaploids and 6x-aneuploid hybrids rather than to the expected triploids. No genuine hybrids were obtained in the reciprocal cross. The pollen diameter of the tetraploid S. megalanthus varied widely, indicating the occurrence of unreduced gametes, while that of H. undatus pollen was very uniform, indicating an extremely low frequency of unreduced gametes. This finding suggests that the hexaploids were formed by chromosome doubling after the formation of the hybrid triploid zygote rather than by fusion of unreduced gametes of the two species.

  9. Ultrasonic investigation of mechanical properties of double base rocket propellants

    NARCIS (Netherlands)

    Schroeff, J.A. van der; Boer, R.S. de

    1976-01-01

    For a series of double base rocket propellants and for poly-methylmethacrylate (PMMA) the longitudinal and transverse sound wave velocities are measured at a frequency of 0.351 MHz in t h e temperature range of −40°C to +60°C. The relations between these acoustic properties and mechanical properties

  10. The Double–Double Radio Galaxy 3C293

    Indian Academy of Sciences (India)

    S. A. Joshi; S. Nandi; D. J. Saikia; C. H. Ishwara-Chandra; C. Konar

    2011-12-01

    We present the results of radio continuum observations at frequencies ranging from ∼ 150–5000 MHz of the misaligned double–double radio galaxy (DDRG) 3C293 (J1352+3126) using the GMRT and the VLA, and estimate the time-scale of interruption of jet activity to be less than ∼ 0.1 Myr.

  11. The use of (double) relaxation oscillation SQUIDs as a sensor

    NARCIS (Netherlands)

    Duuren, van M.J.; Brons, G.C.S.; Kattouw, H.; Flokstra, J.; Rogalla, H.

    1997-01-01

    Relaxation Oscillation SQUIDs (ROSs) and Double Relaxation Oscillation SQUIDs (DROSs) are based on relaxation oscillations that are induced in hysteretic dc SQUIDs by an external L-R shunt. The relaxation frequency of a ROS varies with the applied flux Φ, whereas the output of a DROS is a dc voltage

  12. Analytical Model of Planar Double Split Ring Resonator

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Jensen, Thomas; Krozer, Viktor

    2007-01-01

    This paper focuses on accurate modelling of microstrip double split ring resonators. The impedance matrix representation for coupled lines is applied for the first time to model the SRR, resulting in excellent model accuracy over a wide frequency range. Phase compensation is implemented to take...

  13. The use of (double) relaxation oscillation SQUIDs as a sensor

    NARCIS (Netherlands)

    van Duuren, M.J.; Brons, G.C.S.; Kattouw, H.; Flokstra, Jakob; Rogalla, Horst

    1997-01-01

    Relaxation Oscillation SQUIDs (ROSs) and Double Relaxation Oscillation SQUIDs (DROSs) are based on relaxation oscillations that are induced in hysteretic dc SQUIDs by an external L-R shunt. The relaxation frequency of a ROS varies with the applied flux Φ, whereas the output of a DROS is a dc

  14. High sensitivity double relaxation oscillation superconducting quantum interference devices

    NARCIS (Netherlands)

    Adelerhof, Derk Jan; Adelerhof, Derk Jan; Kawai, Jun; Uehara, Gen; Kado, Hisashi

    1994-01-01

    Double relaxation oscillationsuperconducting quantum interference devices(SQUIDs) (DROSs) have been fabricated with estimated relaxation frequencies up to 14 GHz. Both the intrinsic flux noise and the performance in a flux locked loop with direct voltage readout have been studied. In flux locked

  15. Long segment composite split cord malformation with double bony spur

    Directory of Open Access Journals (Sweden)

    Sharma Anand

    2015-09-01

    Full Text Available A composite type of SCM is very rare and only a few cases have been reported until today. The frequency of composite- type SCM is lower than 1% in the literature. In this report, we presented an unusual case of long segment composite type split cord malformation with double level bony spur with multiple associated bony anomalies.

  16. The Double Star mission

    Directory of Open Access Journals (Sweden)

    Liu

    2005-11-01

    Full Text Available The Double Star Programme (DSP was first proposed by China in March, 1997 at the Fragrant Hill Workshop on Space Science, Beijing, organized by the Chinese Academy of Science. It is the first mission in collaboration between China and ESA. The mission is made of two spacecraft to investigate the magnetospheric global processes and their response to the interplanetary disturbances in conjunction with the Cluster mission. The first spacecraft, TC-1 (Tan Ce means "Explorer", was launched on 29 December 2003, and the second one, TC-2, on 25 July 2004 on board two Chinese Long March 2C rockets. TC-1 was injected in an equatorial orbit of 570x79000 km altitude with a 28° inclination and TC-2 in a polar orbit of 560x38000 km altitude. The orbits have been designed to complement the Cluster mission by maximizing the time when both Cluster and Double Star are in the same scientific regions. The two missions allow simultaneous observations of the Earth magnetosphere from six points in space. To facilitate the comparison of data, half of the Double Star payload is made of spare or duplicates of the Cluster instruments; the other half is made of Chinese instruments. The science operations are coordinated by the Chinese DSP Scientific Operations Centre (DSOC in Beijing and the European Payload Operations Service (EPOS at RAL, UK. The spacecraft and ground segment operations are performed by the DSP Operations and Management Centre (DOMC and DSOC in China, using three ground station, in Beijing, Shanghai and Villafranca.

  17. A Biochemical Double Slit

    Science.gov (United States)

    Kominis, Iannis

    2011-03-01

    Radical-ion-pair reactions, fundamental in photosynthesis and at the basis of the avian magnetic compass mechanism, have been recently shown to offer a rich playground for applying methods and concepts from quantum measurement/quantum information science. We will demonstrate that radical-ion-pair reactions are almost the exact analog of the optical double slit experiment, i.e. Nature has already engineered biochemical reactions performing the act of quantum interference. We will further elaborate on the non-trivial quantum effects pertaining in these reactions and the recent debate on their fundamental theoretical description that these effects have sparked.

  18. Double nanosecond pulses generation in ytterbium fiber laser

    Energy Technology Data Exchange (ETDEWEB)

    Veiko, V. P.; Samokhvalov, A. A., E-mail: samokhvalov.itmo@gmail.com; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N. [Saint-Petersburg State University of Information Technologies, Mechanics and Optics, Kronverksky Pr. 49, Saint Petersburg (Russian Federation); Lednev, V. N. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation); National University of Science and Technology MISiS, Leninskyave., 4, Moscow (Russian Federation); Pershin, S. M. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation)

    2016-06-15

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential “opening” radio pulses with a delay of 0.2–1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

  19. Young's Double Slit Experiment in Quantum Field Theory

    CERN Document Server

    Kenmoku, Masakatsu

    2011-01-01

    Young's double slit experiment is formulated in the framework of canonical quantum field theory in view of the modern quantum optics. We adopt quantum scalar fields instead of quantum electromagnetic fields ignoring the vector freedom in gauge theory. The double slit state is introduced in Fock space corresponding to experimental setup. As observables, expectation values of energy density and positive frequency part of current with respect to the double slit state are calculated which give the interference term. Classical wave states are realized by coherent double slit states in Fock space which connect quantum particle states with classical wave states systematically. In case of incoherent sources, the interference term vanishes by averaging random phase angles as expected.

  20. Firewalls From Double Purity

    CERN Document Server

    Bousso, Raphael

    2013-01-01

    The firewall paradox is often presented as arising from double entanglement, but I argue that more generally the paradox is double purity. Near-horizon modes are purified by the interior, in the infalling vacuum. Hence they cannot also be pure alone, or in combination with any third system, as demanded by unitarity. This conflict arises independently of the Page time, for entangled and for pure states. It implies that identifications of Hilbert spaces cannot resolve the paradox. Traditional complementarity requires the unitary identification of infalling matter with a scrambled subsystem of the Hawking radiation. Extending this map to the infalling vacuum overdetermines the out-state. More general complementarity maps ("A=R_B", "ER=EPR") founder when the near-horizon zone is pure. I argue that pure-zone states span the microcanonical ensemble, and that this suffices to make the horizon a special place. I advocate that the ability to detect the horizon locally, rather than the degree or probability of violence...

  1. The research of power saving frequency conversion speed regulation experiment system

    Institute of Scientific and Technical Information of China (English)

    ZHONG Wei-tang

    2008-01-01

    A power saving frequency difference controlling method was introduced by the double inverter and motor experiment system. The characters of the system under differ-ent loads were investigated. The theoretical analysis and experiment results show the frequency difference method is a ideal power saving speed regulation method for the dou-ble inverter and motor system. The experiment system is simply structured, convenient to operate and provides a new way of character testing for frequency conversion speed regulation.

  2. Nonlinear dynamics and load sharing of double-mesh helical gear train

    OpenAIRE

    Fuchun Yang; Zhenxing Shi; Jianfeng Meng

    2013-01-01

    Dynamic behaviours and load sharing of double-mesh helical gear trains have been studied in this paper. A nonlinear dynamic model of double-mesh helical gear train was established, including torsional vibration, axial vibration, timevarying mesh stiffness and backlashes. The governing equations were solved by Runge-Kutta method. Frequency responses and influences of main parameters to frequency responses were analyzed to determine the vibration characteristics of the system. The d...

  3. Frequency encoding in renal blood flow regulation

    DEFF Research Database (Denmark)

    Marsh, Donald J; Sosnovtseva, Olga; Pavlov, Alexey N;

    2005-01-01

    With a model of renal blood flow regulation, we examined consequences of tubuloglomerular feedback (TGF) coupling to the myogenic mechanism via voltage-gated Ca channels. The model reproduces the characteristic oscillations of the two mechanisms and predicts frequency and amplitude modulation...... of the myogenic oscillation by TGF. Analysis by wavelet transforms of single-nephron blood flow confirms that both amplitude and frequency of the myogenic oscillation are modulated by TGF. We developed a double-wavelet transform technique to estimate modulation frequency. Median value of the ratio of modulation...... TGF cycle to the next. We used a blood pressure signal recorded by telemetry from a conscious rat as the input to the model. Blood pressure fluctuations induced variability in the modulation records similar to those found in the nephron blood flow results. Frequency and amplitude modulation can...

  4. Double Field Theory Inspired Cosmology

    CERN Document Server

    Wu, Houwen

    2014-01-01

    Double field theory proposes a generalized spacetime action possessing manifest T-duality on the level of component fields. We calculate the cosmological solutions of double field theory with vanishing Kalb-Ramond field. It turns out that double field theory provides a more consistent way to construct cosmological solutions than the standard string cosmology. We find two sets of solutions in double field theory cosmology, respecting or violating the strong (weak) constraint. Both sets of solutions naturally contain the pre- and post-big bang evolutions in one single line element. This novel feature opens a window for possible resolution of the cosmic amnesia. We also demonstrate that the scale factor duality in the standard string cosmology is nothing but the T-duality in double field theory. The scale dual dilatons in the standard string cosmology is simply the usual diffeomorphic scalar dilaton $\\phi$ and dual diffeomorphic scalar dilaton $\\tilde\\phi$ in double field theory. Furthermore, we identify the "sh...

  5. Double resonance in the system of coupled Josephson junctions

    Science.gov (United States)

    Shukrinov, Yu. M.; Rahmonov, I. R.; Kulikov, K. V.

    2013-01-01

    The effect of LC shunting on the phase dynamics of coupled Josephson junctions has been examined. It has been shown that additional ( rc) branches appear in the current-voltage characteristics of the junctions when the Josephson frequency ωJ is equal to the natural frequency of the formed resonance circuit ωrc. The effect of the parameters of the system on its characteristics has been studied. Double resonance has been revealed in the system at ωJ = ωrc = 2ωLPW, where ωLPW is the frequency of a longitudinal plasma wave appearing under the parametric-resonance conditions. In this case, electric charge appears in superconducting layers in the interval of the bias current corresponding to the rc branch. The charge magnitude is determined by the accuracy with which the double resonance condition is satisfied. The possibility of the experimental implementation of the effects under study has been estimated.

  6. Perturbed period-doubling bifurcation. II. Experiments on Josephson junctions

    DEFF Research Database (Denmark)

    Eriksen, Gert Friis; Hansen, Jørn Bindslev

    1990-01-01

    We present experimental results on the effect of periodic perturbations on a driven, dynamic system that is close to a period-doubling bifurcation. In the preceding article a scaling law for the change of stability of such a system was derived for the case where the perturbation frequency ωS is c......B as a function of the frequency and the amplitude of the perturbation signal ΔμB(ωS,AS) for a model system, the microwave-driven Josephson tunnel junction, and find reasonable agreement between the experimental results and the theory.......We present experimental results on the effect of periodic perturbations on a driven, dynamic system that is close to a period-doubling bifurcation. In the preceding article a scaling law for the change of stability of such a system was derived for the case where the perturbation frequency ω...

  7. Counting Irreducible Double Occurrence Words

    CERN Document Server

    Burns, Jonathan

    2011-01-01

    A double occurrence word $w$ over a finite alphabet $\\Sigma$ is a word in which each alphabet letter appears exactly twice. Such words arise naturally in the study of topology, graph theory, and combinatorics. Recently, double occurrence words have been used for studying DNA recombination events. We develop formulas for counting and enumerating several elementary classes of double occurrence words such as palindromic, irreducible, and strongly-irreducible words.

  8. Multi-frequency excitation

    KAUST Repository

    Younis, Mohammad I.

    2016-03-10

    Embodiments of multi-frequency excitation are described. In various embodiments, a natural frequency of a device may be determined. In turn, a first voltage amplitude and first fixed frequency of a first source of excitation can be selected for the device based on the natural frequency. Additionally, a second voltage amplitude of a second source of excitation can be selected for the device, and the first and second sources of excitation can be applied to the device. After applying the first and second sources of excitation, a frequency of the second source of excitation can be swept. Using the methods of multi- frequency excitation described herein, new operating frequencies, operating frequency ranges, resonance frequencies, resonance frequency ranges, and/or resonance responses can be achieved for devices and systems.

  9. Colored Flag by Double Refraction.

    Science.gov (United States)

    Reid, Bill

    1994-01-01

    Describes various demonstrations that illustrate double refraction and rotation of the plane of polarization in stressed, transparent plastics, with the consequent production of colored designs. (ZWH)

  10. Double Degenerate Stars

    Institute of Scientific and Technical Information of China (English)

    LUO Xin-Lian; BAI Hua; ZHAO Lei

    2008-01-01

    Regardless of the formation mechanism, an exotic object, the double degenerate star (DDS), is introduced and investigated, which is composed of baryonic matter and some unknown fermion dark matter. Different from the simple white dwarfs (WDs), there is additional gravitational force provided by the unknown fermion component inside DDSs, which may strongly affect the structure and the stability of such kind of objects. Many possible and strange observational phenomena connecting with them are concisely discussed. Similar to the normal WD, this object can also experience thermonuclear explosion as type Ia supernova explosion when DDS's mass exceeds the maximum mass that can be supported by electron degeneracy pressure. However, since the total mass of baryonic matter can be much lower than that of WD at Chandrasekhar mass limit, the peak luminosity should be much dimmer than what we expect before, which may throw a slight shadow on the standard candle of SN Ia in the research of cosmology.

  11. GENERALIZED DOUBLE PARETO SHRINKAGE.

    Science.gov (United States)

    Armagan, Artin; Dunson, David B; Lee, Jaeyong

    2013-01-01

    We propose a generalized double Pareto prior for Bayesian shrinkage estimation and inferences in linear models. The prior can be obtained via a scale mixture of Laplace or normal distributions, forming a bridge between the Laplace and Normal-Jeffreys' priors. While it has a spike at zero like the Laplace density, it also has a Student's t-like tail behavior. Bayesian computation is straightforward via a simple Gibbs sampling algorithm. We investigate the properties of the maximum a posteriori estimator, as sparse estimation plays an important role in many problems, reveal connections with some well-established regularization procedures, and show some asymptotic results. The performance of the prior is tested through simulations and an application.

  12. Dual Double Field Theory

    CERN Document Server

    Bergshoeff, Eric A; Penas, Victor A; Riccioni, Fabio

    2016-01-01

    We present the dual formulation of double field theory at the linearized level. This is a classically equivalent theory describing the duals of the dilaton, the Kalb-Ramond field and the graviton in a T-duality or O(D,D) covariant way. In agreement with previous proposals, the resulting theory encodes fields in mixed Young-tableau representations, combining them into an antisymmetric 4-tensor under O(D,D). In contrast to previous proposals, the theory also requires an antisymmetric 2-tensor and a singlet, which are not all pure gauge. The need for these additional fields is analogous to a similar phenomenon for "exotic" dualizations, and we clarify this by comparing with the dualizations of the component fields. We close with some speculative remarks on the significance of these observations for the full non-linear theory yet to be constructed.

  13. Frequency selectivity at very low centre frequencies

    DEFF Research Database (Denmark)

    Orellana, Carlos Andrés Jurado; Pedersen, Christian Sejer; Marquardt, Torsten

    2010-01-01

    A significant factor in the decrease of sensitivity to low-frequency sound is the helicotrema shunt effect. In humans, it causes a slope increase of the middle-ear transfer function (METF) from 6 dB/oct to 12 dB/oct below approximately 50 Hz [Marquardt et al., J.Acoust. Soc. Am. 121, 3628......-3638 (2007)]. Recent experiments showed that the exact frequency varies from individual to individual. Besides, the helicotrema region in the METF has been found to highly influence frequency selectivity for centre frequencies (CFs) below 80 Hz (Jurado and Moore in prep). By using individual METF...... in the shape of the METFs, thought to be affected by the helicotrema impedance. Preliminary analysis indicates that individual differences in the METFs might underlay the observed individual differences in frequency selectivity. Main effects predicted by the calculations are a pronounced flattening off...

  14. Frequency selective surface with a flat topped passband

    Institute of Scientific and Technical Information of China (English)

    Hongyan Jia; Jinsong Gao; Xiaoguo Feng; Qingwen Meng

    2007-01-01

    Two frequency selective surface (FSS) configurations with flat topped passband are presented in this paper.One configuration is single layer FSS with λ/4 thickness dielectric loaded on both sides, and the other is double layers FSS. Based on the modal matching method, the frequency response properties including angle effect and polarization effect of both FSS configurations are analyzed, and the plots of the frequency versus transmission coefficient are obtained for different incident angles and polarizations. It is shown that the structure with the single layer FSS embedded centrally in the λ/2 thickness dielectric has a wider flat top bandwidth of 6.8 GHz than that of the double layers FSS of 3 GHz. In addition, the fabrication of single layer is relatively easier than the double layers FSS.

  15. Period Doubling in a Fabry-Perot Laser Diode Subject to Optical Pulse Injection

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yue-Peng; WANG Yun-Cai; ZHANG Ming-Jiang; AN Yi; WANG Ji-Long

    2007-01-01

    Experimental study and numerical simulations of the period doubling of injected optical pulses in Fabry-Perot laser diodes are presented. In our experiments, the period doubling is achieved within a wide input frequency range and the period doubling of the injected optical pulses with 6.32 GHz repetition rate is investigated in detail. The obtained experimental results indicate that period doubling occurs at an appropriate injected optical power level when the bias current of the Fabry-Perot laser diode is located in lower ranges. Moreover, the experimental observed features have been numerically demonstrated by using a coupled rate-equation model. Numerical simulations are consistent with the experimental results.

  16. Hedging Double Barriers with Singles

    NARCIS (Netherlands)

    Sbuelz, A.

    2000-01-01

    Double barrier options provide risk managers with good-deal flexibility in tailoring portfolio returns.Their hedges offer full protection only if unwound along the barriers.This work provides non-dynamic hedges that project the risk of double barriers on to single barriers.Non-dynamic hedges overcom

  17. Properties of double field theory

    NARCIS (Netherlands)

    Penas, Victor Alejandro

    2016-01-01

    In this thesis we study several aspects of Double Field Theory (DFT). In general, Double Field Theory is subject to the so-called strong constraint. By using the Flux Formulation of DFT, we explore to what extent one can deal with the gauge consistency constraints of DFT without imposing the strong

  18. Electric double layer of anisotropic dielectric colloids under electric fields

    Science.gov (United States)

    Han, M.; Wu, H.; Luijten, E.

    2016-07-01

    Anisotropic colloidal particles constitute an important class of building blocks for self-assembly directed by electrical fields. The aggregation of these building blocks is driven by induced dipole moments, which arise from an interplay between dielectric effects and the electric double layer. For particles that are anisotropic in shape, charge distribution, and dielectric properties, calculation of the electric double layer requires coupling of the ionic dynamics to a Poisson solver. We apply recently proposed methods to solve this problem for experimentally employed colloids in static and time-dependent electric fields. This allows us to predict the effects of field strength and frequency on the colloidal properties.

  19. Nanomechanical characterization by double-pass force-distance mapping

    Energy Technology Data Exchange (ETDEWEB)

    Dagdas, Yavuz S; Tekinay, Ayse B; Guler, Mustafa O; Dana, Aykutlu [UNAM Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey); Necip Aslan, M, E-mail: aykutlu@unam.bilkent.edu.tr [Department of Physics, Istanbul Technical University, Istanbul (Turkey)

    2011-07-22

    We demonstrate high speed force-distance mapping using a double-pass scheme. The topography is measured in tapping mode in the first pass and this information is used in the second pass to move the tip over the sample. In the second pass, the cantilever dither signal is turned off and the sample is vibrated. Rapid (few kHz frequency) force-distance curves can be recorded with small peak interaction force, and can be processed into an image. Such a double-pass measurement eliminates the need for feedback during force-distance measurements. The method is demonstrated on self-assembled peptidic nanofibers.

  20. Control of Bouncing in MEMS Switches Using Double Electrodes

    KAUST Repository

    Abdul Rahim, Farhan

    2016-08-09

    This paper presents a novel way of controlling the bouncing phenomenon commonly present in the Radio Frequency Microelectromechanical Systems (RF MEMS) switches using a double-electrode configuration. The paper discusses modeling bouncing using both lumped parameter and beam models. The simulations of bouncing and its control are discussed. Comparison between the new proposed method and other available control techniques is also made. The Galerkin method is applied on the beam model accounting for the nonlinear electrostatic force, squeeze film damping, and surface contact effect. The results indicate that it is possible to reduce bouncing and hence beam degradation, by the use of double electrodes.

  1. Gain of double-slab Cherenkov free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Li, D. [Institute for laser Technology, suita, Osaka 565-0871 (Japan)], E-mail: dazhi_li@hotmail.com; Huo, G. [Petroleum development center, Shengli Oilfield, SINOPEC, Dongying 257001 (China); Imasak, K. [Institute for laser Technology, suita, Osaka 565-0871 (Japan); Asakawa, M. [Department of pure and applied physics, Faculty of Engineering Science, Kansai University, Osaka 564-8680 (Japan)

    2009-07-21

    A formula is derived for the small-signal gain of a double-slab Cherenkov free-electron laser. The simplified model is composed of a rectangular wave-guide partially filled with two lined parallel dielectric slabs and a sheet electron beam. The theory describes the electron beam as a plasma dielectric moving between the two dielectric slabs. With the help of hydrodynamic approximation, we derived the dispersion equation and the formula of small-signal gain. Through numerical computing, we studied an ongoing experiment of double-slab Cherenkov free-electron laser, and worked out the synchronous frequency and single-pass gain.

  2. Study on Pollen Chromosome Doubling in Zenjimaru Persimmon

    Institute of Scientific and Technical Information of China (English)

    GU Xiao-feng; LUO Zheng-rong

    2003-01-01

    The factors influencing pollen chromosome doubling in Zenjimaru persimmon were studied,based on the knowledge of meiosis process of pollen mother cells. The results showed: (1) the suitable concen-tration of colchicine was 0.3 - 0.5%; (2) the best doubling effect could be obtained during the period fromthe dipiotene stage to the diakinasis stage, and the highest proportion was up to 40.6 %; (3) considering giantpollen ratio and proportion of staminate-flower collection, the better treating frequency was 3 times; (4) giantpollen, which formed mainly from dyad and had bigger cell nucleus volume, was unreduced and hexaploid.

  3. Single-frequency operation of a diode-pumped green laser using multi-Brewster plates

    Institute of Scientific and Technical Information of China (English)

    Quan Zheng(郑权); Ling Zhao(赵岭); Longsheng Qian(钱龙生)

    2003-01-01

    In a diode-pumped, KTP intracavity frequency-doubled green laser, multi-Brewster plates are used toachieve high power single-frequency operation. With a simple experimental setup, single-frequency opera-tion of the diode-pumped green laser with output of 46 and 218 mW is obtained by one and three Brewsterplate, respectively.

  4. Frequency adjustable MEMS vibration energy harvester

    Science.gov (United States)

    Podder, P.; Constantinou, P.; Amann, A.; Roy, S.

    2016-10-01

    Ambient mechanical vibrations offer an attractive solution for powering the wireless sensor nodes of the emerging “Internet-of-Things”. However, the wide-ranging variability of the ambient vibration frequencies pose a significant challenge to the efficient transduction of vibration into usable electrical energy. This work reports the development of a MEMS electromagnetic vibration energy harvester where the resonance frequency of the oscillator can be adjusted or tuned to adapt to the ambient vibrational frequency. Micro-fabricated silicon spring and double layer planar micro-coils along with sintered NdFeB micro-magnets are used to construct the electromagnetic transduction mechanism. Furthermore, another NdFeB magnet is adjustably assembled to induce variable magnetic interaction with the transducing magnet, leading to significant change in the spring stiffness and resonance frequency. Finite element analysis and numerical simulations exhibit substantial frequency tuning range (25% of natural resonance frequency) by appropriate adjustment of the repulsive magnetic interaction between the tuning and transducing magnet pair. This demonstrated method of frequency adjustment or tuning have potential applications in other MEMS vibration energy harvesters and micromechanical oscillators.

  5. The Cambridge double star atlas

    CERN Document Server

    MacEvoy, Bruce; Mullaney, James; Tirion, Wil; Mullaney, James

    2015-01-01

    The Cambridge Double Star Atlas is back! It is the first and only atlas of physical double stars that can be viewed with amateur astronomical instruments. Completely rewritten, this new edition explains the latest research into double stars, and looks at the equipment, techniques and opportunities that will enable you to discover, observe and measure them. The target list has been completely revised and extended to 2500 binary or multiple systems. Each system is described with the most recent and accurate data from the authoritative Washington Double Star Catalog, including the HD and SAO numbers that are most useful in our digital age. Hundreds of remarks explain the attributes of local, rapidly changing, often measured or known orbital systems. The color atlas charts by Wil Tirion have been updated to help you easily find and identify the target systems, as well as other deep-sky objects. This is an essential reference for double star observers..

  6. Synchrotron radiation VUV double photoionization of some small molecules

    Institute of Scientific and Technical Information of China (English)

    Zhao Yu-Jie; Shan Xiao-Bin; Sheng Liu-Si; Wang Zhen-Ya; Zhang Jie; Yu Chun-Ri

    2011-01-01

    The VUV double photoionizations of small molecules(NO, CO, CO2, CS2, OSC and NH3)were investigated with photoionization mass spectroscopy using synchrotron radiation. The double ionization energies of molecules were determined with photoionization efficiency spectroscopy. The total energies of these molecules and their parent dications (NO2+, CO2+, CO2+2,CS2+2,OS2+C and NH2+3)were calculated using the Gaussian 03 program and Gaussian 2calculations. Then, the adiabatic double ionization energies of the molecules were predicated by using high accuracy energy mode. The experimental double ionization energies of these small molecules were all in reasonable agreement with their respective calculated adiabatic double ionization energies. The mechanisms of double photoionization of these molecules were discussed based on a comparison of our experimental results with those predicted theoretically. The equilibrium geometries and harmonic vibrational frequencies of molecules and their parent dications were calculated by using the MP2(full)method. The differences in configurations between these molecules and their parent dications were also discussed on the basis of theoretical calculations.

  7. Laser double Doppler flowmeter

    Science.gov (United States)

    Poffo, L.; Goujon, J.-M.; Le Page, R.; Lemaitre, J.; Guendouz, M.; Lorrain, N.; Bosc, D.

    2014-05-01

    The Laser Doppler flowmetry (LDF) is a non-invasive method for estimating the tissular blood flow and speed at a microscopic scale (microcirculation). It is used for medical research as well as for the diagnosis of diseases related to circulatory system tissues and organs including the issues of microvascular flow (perfusion). It is based on the Doppler effect, created by the interaction between the laser light and tissues. LDF measures the mean blood flow in a volume formed by the single laser beam, that penetrate into the skin. The size of this measurement volume is crucial and depends on skin absorption, and is not directly reachable. Therefore, current developments of the LDF are focused on the use of always more complex and sophisticated signal processing methods. On the other hand, laser Double Doppler Flowmeter (FL2D) proposes to use two laser beams to generate the measurement volume. This volume would be perfectly stable and localized at the intersection of the two laser beams. With FL2D we will be able to determine the absolute blood flow of a specific artery. One aimed application would be to help clinical physicians in health care units.

  8. Double Chooz: Latest results

    CERN Document Server

    Crespo-Anadón, J I

    2014-01-01

    The latest results from the Double Chooz experiment on the neutrino mixing angle $\\theta_{13}$ are presented. A detector located at an average distance of 1050 m from the two reactor cores of the Chooz nuclear power plant has accumulated a live time of 467.90 days, corresponding to an exposure of 66.5 GW-ton-year (reactor power $\\times$ detector mass $\\times$ live time). A revised analysis has boosted the signal efficiency and reduced the backgrounds and systematic uncertainties compared to previous publications, paving the way for the two detector phase. The measured $\\sin^2 2\\theta_{13} = 0.090^{+0.032}_{-0.029}$ is extracted from a fit to the energy spectrum. A deviation from the prediction above a visible energy of 4 MeV is found, being consistent with an unaccounted reactor flux effect, which does not affect the $\\theta_{13}$ result. A consistent value of $\\theta_{13}$ is measured in a rate-only fit to the number of observed candidates as a function of the reactor power, confirming the robustness of the ...

  9. Double acting bit holder

    Science.gov (United States)

    Morrell, Roger J.; Larson, David A.; Ruzzi, Peter L.

    1994-01-01

    A double acting bit holder that permits bits held in it to be resharpened during cutting action to increase energy efficiency by reducing the amount of small chips produced. The holder consist of: a stationary base portion capable of being fixed to a cutter head of an excavation machine and having an integral extension therefrom with a bore hole therethrough to accommodate a pin shaft; a movable portion coextensive with the base having a pin shaft integrally extending therefrom that is insertable in the bore hole of the base member to permit the moveable portion to rotate about the axis of the pin shaft; a recess in the movable portion of the holder to accommodate a shank of a bit; and a biased spring disposed in adjoining openings in the base and moveable portions of the holder to permit the moveable portion to pivot around the pin shaft during cutting action of a bit fixed in a turret to allow front, mid and back positions of the bit during cutting to lessen creation of small chip amounts and resharpen the bit during excavation use.

  10. Double-double electromagnetically induced transparency with amplification

    CERN Document Server

    Alotaibi, Hessa M M

    2013-01-01

    We show that an alkali atom with a tripod electronic structure can yield rich electromagnetically induced transparency phenomena even at room temperature. In particular we introduce double-double electromagnetically induced transparency wherein signal and probe fields each have two transparency windows. Their group velocities can be matched in either the first or second pair of transparency windows. Moreover signal and probe fields can each experience coherent gain in the second transparency windows. We explain using a semi-classical-dressed-picture to connect the tripod electronic structure to a double-\\Lambda\\ scheme.

  11. Hyperfine phononic frequency comb

    CERN Document Server

    Ganesan, Adarsh; Seshia, Ashwin A

    2016-01-01

    Optical frequency combs [1-8] have resulted in significant advances in optical frequency metrology and found wide application to precise physical measurements [1-4, 9] and molecular fingerprinting [8]. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this letter, we report the first clear experimental evidence for a phononic frequency comb. In contrast to the Kerr nonlinearity [10] in optical frequency comb formation, the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an auto-parametrically excited sub-harmonic mode [16]. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define attributes to control the features [17-18] associated with comb formation in such a system. Further, the interplay between these nonlinear resonances and the well-known Duffing phenomenon [12-14] is also observed. The present...

  12. Static electromagnetic frequency changers

    CERN Document Server

    Rozhanskii, L L

    1963-01-01

    Static Electromagnetic Frequency Changers is about the theory, design, construction, and applications of static electromagnetic frequency changers, devices that used for multiplication or division of alternating current frequency. It is originally published in the Russian language. This book is organized into five chapters. The first three chapters introduce the readers to the principles of operation, the construction, and the potential applications of static electromagnetic frequency changers and to the principles of their design. The two concluding chapters use some hitherto unpublished work

  13. Modeling Frequency Comb Sources

    Directory of Open Access Journals (Sweden)

    Li Feng

    2016-06-01

    Full Text Available Frequency comb sources have revolutionized metrology and spectroscopy and found applications in many fields. Stable, low-cost, high-quality frequency comb sources are important to these applications. Modeling of the frequency comb sources will help the understanding of the operation mechanism and optimization of the design of such sources. In this paper,we review the theoretical models used and recent progress of the modeling of frequency comb sources.

  14. Evolution of Bell- nonlocality of two cavity fields in the double Jaynes-Cummings model

    Institute of Scientific and Technical Information of China (English)

    Long Miao; Yunkun Jiang

    2011-01-01

    The Bell-nonlocality of two initially entangled macroscopic fields in the double Jaynes-Cummings model is investigated.Moreover,the process by which detuning between the atomic transition frequency and the field frequency affects the evolution of the Bell-nonlocality of two macroscopic fields is studied.The effect of the disparity between the two coupling strengths is discussed.

  15. Eastern Frequency Response Study

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.W.; Shao, M.; Pajic, S.; D' Aquila, R.

    2013-05-01

    This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.

  16. Transversal vibrations of double-plate systems

    Institute of Scientific and Technical Information of China (English)

    Katica(Stevanovi(c)) Hedrih

    2006-01-01

    This paper presents an analytical and numerical analysis of free and forced transversal vibrations of an elastically connected double-plate system. Analytical solutions of a system of coupled partial differential equations, which describe corresponding dynamical free and forced processes, are obtained using Bernoulli's particular integral and Lagrange's method of variation constants. It is shown that one-mode vibrations correspond to two-frequency regime for free vibrations induced by initial conditions and to three-frequency regime for forced vibrations induced by one-frequency external excitation and corresponding initial conditions. The analytical solutions show that the elastic connection between plates leads to the appearance of twofrequency regime of time function, which corresponds to one eigenamplitude function of one mode, and also that the time functions of different vibration modes are uncoupled, for each shape of vibrations. It has been proven that for both elastically connected plates, for every pair of m and n. two possibilities for appearance of the resonance dynamical states, as well as for appearance of the dynamical absorption, are present. Using the MathCad program, the corresponding visualizations of the characteristic forms of the plate middle surfaces through time are presented.

  17. Aspects of the Doubled Worldsheet

    CERN Document Server

    Driezen, Sibylle; Thompson, Daniel C

    2016-01-01

    We clarify the relation between various approaches to the manifestly T-duality symmetric string. We explain in detail how the PST covariant doubled string arises from an unusual gauge fixing. We pay careful attention to the role of "spectator" fields in this process and also show how the T-duality invariant doubled dilaton emerges naturally. We extend these ideas to non-Abelian T-duality and show they give rise to the duality invariant formalism based on the semi-Abelian Drinfeld Double. We then develop the N=(0,1) supersymmetric duality invariant formalism.

  18. Frequency selective infrared sensors

    Science.gov (United States)

    Davids, Paul; Peters, David W

    2013-05-28

    A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

  19. Don't Double Up on Acetaminophen

    Science.gov (United States)

    ... For Consumers Home For Consumers Consumer Updates Don't Double Up on Acetaminophen Share Tweet Linkedin Pin ... consumer organizations. AAC’s outreach campaign, "Double Check, Don't Double Up," is all about the safe use ...

  20. Hitchcock’s queer doubles

    Directory of Open Access Journals (Sweden)

    Alessandra Brandão

    2013-12-01

    Full Text Available http://dx.doi.org/10.5007/2175-8026.2013n65p17   The “double” is a well-known Hitchcockian motif. Widelyreviewed under a psychoanalytical perspective, the issue ofthe double still presents other important challenges and thisarticle aims at discussing the queer doubles in Hitchcock’s films as “falsifiers” who are opposed to non-queer doubles thatemphasise narrative coherence and legibility. In films such asRebeca, Rope, Vertigo, The Birds, Psycho, and Frenzy, a doublecondenses impulses that are well described by Lee Edelman: “theviolent undoing of meaning, the loss of identity and coherence,the unnatural access to jouissance” (132. These doubles releasethe powers of the false as they complicate the return to an “order”.Therefore, we could argue that such characters are closer tobeing Deleuzian simulacra than psychoanalytical doppelgängers.

  1. Gas-filled double glazing

    Energy Technology Data Exchange (ETDEWEB)

    Goesele, K.; Schuele, W.; Lakatos, B.

    1982-01-01

    On the basis of the results of experiments the sonar and thermal properties of insulated double glazing filled with gas are tested. The sound insulation properties of double glazing can be improved by introducing a gas of a heavy specific weight, such as CO/sub 2/ or SF/sub 6/ into the hollow space. Even gases with a light specific weight produce an improvement in sound insulation; light gases diffuse outwards much more rapidly, however, and can thus be eliminated for practical purposes. The combination of a gas-filled space between the panes and the use of sufficiently heavy compound panes were tested. The thermal properties of insulated double glazing filled with specifically heavy gas gave favourable results with a lower heat transition coefficient. The use of gas to fill double glazing has a particularly favourable effect if the panes are given a heat-reflecting coating in synthetic frames.

  2. Oceanic double-infusion: introduction

    Science.gov (United States)

    Ruddick, Barry; Gargett, Ann E.

    2003-03-01

    Double-diffusion, the mixing of fluids with two constituents of different molecular diffusivities, was originally discovered in the mid-1800s, forgotten, then rediscovered as an ‘oceanographic curiosity’ a century later. Many oceanographers suspect that double-diffusion has major effects on oceanic water masses and circulation, but direct measurement of the effects has proven difficult. In 1996, a Working Group was formed under the auspices of the Scientific Committee on Ocean Research (SCOR WG108), with the goal to identify progress and barriers to quantifying oceanic double-diffusive fluxes, and make recommendations for further progress. This document gives a brief history of double-diffusion, a review of evidence of its potential effects in the ocean, and gives an overview of the review articles contained in this volume, written by the Working Group members with the above aim in mind.

  3. The Double Love Commandment

    Directory of Open Access Journals (Sweden)

    Francois P. Viljoen

    2015-03-01

    Full Text Available The Gospel of Matthew was written during a period of dispute between the Matthean community and their fellow Jews, with the Pharisees playing a leading role. The Matthean community was heir to the same scriptures as its opponents. They continued to have a firm commitment to the Torah, but they developed a distinctive understanding of it based on Jesus’ teaching. The formation of this community is investigated in this article, considering the Mediterranean perspectives of group-oriented societies prevalent in the first century. Such a group provided a sense of self and an interactive support system, where love functioned to bind the group together. The subordinates showed their undivided loyalty towards their superiors because of the favours they received from them, whilst they supported and cared for other members within the group as they care for themselves. Reading the double love commandment of Matthew 22:34−40 from this perspective reveals significant aspects of the community’s identity with regard to their commitment to God and their view of their neighbours.Die Dubbele Liefdesgebod. Die Matteusevangelie is gedurende ’n periode van konfliktussen die Matteusgemeenskap en mede-Jode geskryf met die Fariseërs in ’n leidende rol. Die Matteusgemeenskap het van dieselfde geskrifte as hulle opponente gebruik gemaak. Hulle was steeds aan die Torah lojaal, maar het ’n unieke interpretasie daarvan gehuldig, gebaseer op die onderrig van Jesus. In hierdie artikel word die vorming van die Matteusgemeenskap ondersoek met inagneming van die Mediterreense beskouing van die groepgeoriënteerde gemeenskappe wat tipies van die eerste eeu was. So ’n groep het aan individue ’n bewustheid van eie waarde verskaf te midde van ’n interaktiewe ondersteuningsisteem waarin liefde as samebindende faktor gefunksioneer het. Ondergeskiktes het onverdeelde lojaliteit teenoor hulle meerderes betoon vanweë die gunste wat hulle van die meerderes geniet het

  4. Transmission of Sound Through Double-Plate Panel Structures

    DEFF Research Database (Denmark)

    Dickow, Kristoffer Ahrens; Domadiya, Parthkumar Gandalal; Andersen, Lars;

    2011-01-01

    In the present paper, a finite-element model of a double-plate panel is implemented to investigate the transmission of sound through a simple lightweight structure. A numerical study is performed of the following three coupling configurations: 1) Structure-borne sound via plate......-stud-plate structures without air inclusions; 2) transmission via the plate-stud-plate structure including the internal acoustic medium; 3) transmission via plate-air-plate connections in a double-leaf panel with no structural coupling between the two plates. A fully coupled analysis is performed in which solid finite...... elements are adopted for the structure, whereas the acoustic medium is discretized into fluid continuum elements. The computations are carried out in frequency domain in the low frequency range and the load acts as a diffuse sound field on one side of the panel....

  5. Transmission of Sound Through Double-Plate Panel Structures

    DEFF Research Database (Denmark)

    Dickow, Kristoffer Ahrens; Domadiya, Parthkumar Gandalal; Andersen, Lars

    2011-01-01

    In the present paper, a finite-element model of a double-plate panel is implemented to investigate the transmission of sound through a simple lightweight structure. A numerical study is performed of the following three coupling configurations: 1) Structure-borne sound via plate-stud-plate structu......In the present paper, a finite-element model of a double-plate panel is implemented to investigate the transmission of sound through a simple lightweight structure. A numerical study is performed of the following three coupling configurations: 1) Structure-borne sound via plate...... elements are adopted for the structure, whereas the acoustic medium is discretized into fluid continuum elements. The computations are carried out in frequency domain in the low frequency range and the load acts as a diffuse sound field on one side of the panel....

  6. Vibration and Acoustic Radiation from Submerged Spherical Double-Shell

    Institute of Scientific and Technical Information of China (English)

    陈军明; 黄玉盈; 陈应波

    2003-01-01

    Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employed to introduce the forces and moments applied by the attachments, and by means of expanding field quantities as the Legendre series, a semi-analytic solution is derived for the solution to the vibration and acoustic radiation from a submerged spherical double-shell. This solution has a satisfying computational effectiveness and precision for arbitrary frequency range excitation. It is concluded that the internal plates attached to shells can change significantly the mechanical and acoustical characteristics of shells, and make the coupling system have a very rich resonance frequency spectrum. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.

  7. Double diffraction in an atomic gravimeter

    CERN Document Server

    Malossi, Nicola; Merlet, Sébastien; Landragin, Arnaud; Santos, Franck Pereira Dos

    2009-01-01

    We demonstrate the realization of a new scheme for cold atom gravimetry based on the use of double diffraction beamsplitters recently demonstrated in \\cite{Leveque}, where the use of two retro-reflected Raman beams allows symmetric diffraction in $\\pm \\hbar k_{eff}$ momenta. Though in principle restricted to the case of zero Doppler shift, for which the two pairs of Raman beams are simultaneously resonant, we demonstrate that such diffraction pulses can remain efficient on atoms with non zero velocity, such as in a gravimeter, when modulating the frequency of one of the two Raman laser sources. We use such pulses to realize an interferometer insensitive to laser phase noise and some of the dominant systematics. This reduces the technical requirements and would allow the realization of a simple atomic gravimeter. We demonstrate a sensitivity of $1.2\\times10^{-7}g$ per shot.

  8. Energy transfer in double plate system dynamics

    Institute of Scientific and Technical Information of China (English)

    Katica (Stevanovic) Hedrih

    2008-01-01

    The study of energy transfer between coupled subsystems in a hybrid system is very important for applications. This paper presents an analytical analysis of energy transfer between plates of a visco-elastically connected double-plate system in free transversal vibrations. The analytical analysis shows that the visco-elastic connection between plates is responsible for the appearance of two-frequency regime in the time function, which corresponds to one eigen amplitude function of one mode, and also that time functions of different vibration modes are uncoupled, but energy transfer between plates in one eigen mode appears. It was shown for each shape of vibrations. Series of the two Lyapunov exponents corresponding to the one eigen amplitude mode are expressed by using the energy of the corresponding eigen amplitude time component.

  9. Period-doubling cascades galore

    OpenAIRE

    Sander, Evelyn; Yorke, James A.

    2009-01-01

    The appearance of numerous period-doubling cascades is among the most prominent features of {\\bf parametrized maps}, that is, smooth one-parameter families of maps $F:R \\times {\\mathfrak M} \\to {\\mathfrak M}$, where ${\\mathfrak M}$ is a smooth locally compact manifold without boundary, typically $R^N$. Each cascade has infinitely many period-doubling bifurcations, and it is typical to observe -- such as in all the examples we investigate here -- that whenever there are any cascades, there are...

  10. Double parton scattering in CMS

    CERN Document Server

    Sunar Cerci, Deniz

    2017-01-01

    Recent results on the double parton scattering measurements performed using the proton-proton collision data collected with the CMS detector are presented. The observables, which are sensitive to double parton scattering, are investigated after being corrected for detector effects and selection efficiencies. Multivariate analysis techniques are used for increasing the sensitivity. The effective cross section, $\\sigma_{eff}$ is also extracted using different processes at various center-of-mass energies.

  11. Alignment in double capture processes

    Energy Technology Data Exchange (ETDEWEB)

    Moretto-Capelle, P.; Benhenni, M.; Bordenave-Montesquieu, A.; Benoit-Cattin, P.; Gleizes, A. (IRSAMC, URA CNRS 770, Univ. Paul Sabatier, 118 rte de Narbonne, 31062 Toulouse Cedex (France))

    1993-06-05

    The electron spectra emitted when a double capture occurs in N[sup 7+]+He and Ne[sup 8+]+He systems at 10 qkeV collisional energy, allow us to determine the angular distributions of the 3[ell]3[ell] [prime] lines through a special spectra fitting procedure which includes interferences between neighbouring states. It is found that the doubly excited states populated in double capture processes are generally aligned.

  12. Equivalent electron correlations in nonsequential double ionization of noble atoms

    Science.gov (United States)

    Dong, Shansi; Han, Qiujing; Zhang, Jingtao

    2017-02-01

    Electron correlation is encoded directly in the distribution of the energetic electrons produced in a recollision-impact double ionization process, and varies with the laser field and the target atoms. In order to get equivalent electron correlation effects, one should enlarge the laser intensity cubically and the laser frequency linearly in proportion to the second ionization potentials of the target atoms. The physical mechanism behind the transform is to keep the ponderomotive parameter unchanged when the laser frequency is enlarged. Project supported by the National Natural Science Foundation of China (Grant Nos. 61475168 and 11674231) and sponsored by Shanghai Gaofeng & Gaoyuan Project for University Academic Program Development (Zhang).

  13. An alternative technique for timing the double pulsar system

    CERN Document Server

    Liang, Zhu-Xing

    2012-01-01

    Freire et al. (2009, MNRAS, 396, 1764) have put forward a technique for timing the double pulsar system PSR J0737-3039A/B (hereafter A and B, respectively). Their technique can be used to determine the sense of rotation of A relative to its orbital plane. In this paper, we present another technique with the same purpose. Two well-known periods, the sidereal day and solar day, are often used to define the spin period of the earth. Their difference is caused by a kinematic effect which correlated with earth's rotation and revolution. We think that this kinematic effect should exist in the double pulsar system and can be used to determine the sense of rotation of the pulsars. Commonly, B's modulation frequency is considered to be equal to A's rotation frequency, because B's signal is modulated by A's energy flux. When the kinematic effect is considered, B's modulation frequency will be, similar to the solar day and sidereal day, a little higher or lower than A's rotation frequency. If this frequency offset can b...

  14. Radio frequency detection assembly and method for detecting radio frequencies

    Science.gov (United States)

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  15. Waveform frequency notching

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W.; Andrews, John

    2017-05-09

    The various technologies presented herein relate to incorporating one or more notches into a radar spectrum, whereby the notches relate to one or more frequencies for which no radar transmission is to occur. An instantaneous frequency is monitored and if the frequency is determined to be of a restricted frequency, then a radar signal can be modified. Modification can include replacing the signal with a signal having a different instantaneous amplitude, a different instantaneous phase, etc. The modification can occur in a WFS prior to a DAC, as well as prior to a sin ROM component and/or a cos ROM component. Further, the notch can be dithered to enable formation of a deep notch. The notch can also undergo signal transitioning to enable formation of a deep notch. The restricted frequencies can be stored in a LUT against which an instantaneous frequency can be compared.

  16. Universal Optical Frequency Comb

    CERN Document Server

    Savchenkov, A A; Liang, W; Ilchenko, V S; Seidel, D; Maleki, L

    2010-01-01

    We demonstrate that whispering gallery mode resonators can be utilized to generate optical frequency combs based on four wave mixing process at virtually any frequency that lies in the transparency window of the resonator host material. We show theoretically how the morphology of the resonator can be engineered to produce a family of spectrally equidistant modes with anomalous group velocity dispersion appropriate for the comb generation. We present experimental results for a frequency comb centered at 794 nm to support our theoretical findings.

  17. Frequency of atopy in the Arctic in 1987 and 1998

    DEFF Research Database (Denmark)

    Krause, Tyra; Koch, Anders; Friborg, Jeppe

    2002-01-01

    atopy as a positive result in an assay that tests for specific IgE against the eight most common inhalant allergens in one pool (grass, birch, mugwort, dog, cat, horse, Cladosporum herbarum, house dust mite). The frequency of atopy doubled between 1987 (39 [10%] of 392) and 1998 (87 [19%] of 467; risk...

  18. Probability and Relative Frequency

    Science.gov (United States)

    Drieschner, Michael

    2016-01-01

    The concept of probability seems to have been inexplicable since its invention in the seventeenth century. In its use in science, probability is closely related with relative frequency. So the task seems to be interpreting that relation. In this paper, we start with predicted relative frequency and show that its structure is the same as that of probability. I propose to call that the `prediction interpretation' of probability. The consequences of that definition are discussed. The "ladder"-structure of the probability calculus is analyzed. The expectation of the relative frequency is shown to be equal to the predicted relative frequency. Probability is shown to be the most general empirically testable prediction.

  19. Frequency Response Analysis Tool

    Energy Technology Data Exchange (ETDEWEB)

    Etingov, Pavel V.; Kosterev, Dmitry; Dai, T.

    2014-12-31

    Frequency response has received a lot of attention in recent years at the national level, which culminated in the development and approval of North American Electricity Reliability Corporation (NERC) BAL-003-1 Frequency Response and Frequency Bias Setting Reliability Standard. This report is prepared to describe the details of the work conducted by Pacific Northwest National Laboratory (PNNL) in collaboration with the Bonneville Power Administration and Western Electricity Coordinating Council (WECC) Joint Synchronized Information Subcommittee (JSIS) to develop a frequency response analysis tool (FRAT). The document provides the details on the methodology and main features of the FRAT. The tool manages the database of under-frequency events and calculates the frequency response baseline. Frequency response calculations are consistent with frequency response measure (FRM) in NERC BAL-003-1 for an interconnection and balancing authority. The FRAT can use both phasor measurement unit (PMU) data, where available, and supervisory control and data acquisition (SCADA) data. The tool is also capable of automatically generating NERC Frequency Response Survey (FRS) forms required by BAL-003-1 Standard.

  20. Frequency Response Analysis Tool

    Energy Technology Data Exchange (ETDEWEB)

    Etingov, Pavel V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kosterev, Dmitry [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dai, T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-12-01

    Frequency response has received a lot of attention in recent years at the national level, which culminated in the development and approval of North American Electricity Reliability Corporation (NERC) BAL-003-1 Frequency Response and Frequency Bias Setting Reliability Standard. This report is prepared to describe the details of the work conducted by Pacific Northwest National Laboratory (PNNL) in collaboration with the Bonneville Power Administration and Western Electricity Coordinating Council (WECC) Joint Synchronized Information Subcommittee (JSIS) to develop a frequency response analysis tool (FRAT). The document provides the details on the methodology and main features of the FRAT. The tool manages the database of under-frequency events and calculates the frequency response baseline. Frequency response calculations are consistent with frequency response measure (FRM) in NERC BAL-003-1 for an interconnection and balancing authority. The FRAT can use both phasor measurement unit (PMU) data, where available, and supervisory control and data acquisition (SCADA) data. The tool is also capable of automatically generating NERC Frequency Response Survey (FRS) forms required by BAL-003-1 Standard.

  1. Optimization of frequency quantization

    CERN Document Server

    Tibabishev, V N

    2011-01-01

    We obtain the functional defining the price and quality of sample readings of the generalized velocities. It is shown that the optimal sampling frequency, in the sense of minimizing the functional quality and price depends on the sampling of the upper cutoff frequency of the analog signal of the order of the generalized velocities measured by the generalized coordinates, the frequency properties of the analog input filter and a maximum sampling rate for analog-digital converter (ADC). An example of calculating the frequency quantization for two-tier ADC with an input RC filter.

  2. A deep-UV optical frequency comb at 205 nm.

    Science.gov (United States)

    Peters, E; Diddams, S A; Fendel, P; Reinhardt, S; Hänsch, T W; Udem, Th

    2009-05-25

    By frequency quadrupling a picosecond pulse train from a Ti:sapphire laser at 820 nm we generate a frequency comb at 205 nm with nearly bandwidth-limited pulses. The nonlinear frequency conversion is accomplished by two successive frequency doubling stages that take place in resonant cavities that are matched to the pulse repetition rate of 82 MHz. This allows for an overall efficiency of 4.5 % and produces an output power of up to 70 mW for a few minutes and 25 mW with continuous operation for hours. Such a deep UV frequency comb may be employed for direct frequency comb spectroscopy in cases where it is less efficient to convert to these short wavelengths with continuous wave lasers.

  3. Double-Difference Adjoint Tomography

    Science.gov (United States)

    Yuan, Yanhua O.; Simons, Frederik J.; Tromp, Jeroen

    2016-04-01

    We introduce a double-difference method for the inversion of seismic wavespeed structure by adjoint tomography. Differences between seismic observations and model-based predictions at individual stations may arise from factors other than structural heterogeneity, such as errors in the assumed source-time function, inaccurate timings, and systematic uncertainties. To alleviate the corresponding nonuniqueness in the inverse problem, we construct differential measurements between stations, thereby largely canceling out the source signature and systematic errors. We minimize the discrepancy between observations and simulations in terms of differential measurements made on station pairs. We show how to implement the double-difference concept in adjoint tomography, both theoretically and in practice. We compare the sensitivities of absolute and differential measurements. The former provide absolute information on structure along the ray paths between stations and sources, whereas the latter explain relative (and thus higher-resolution) structural variations in areas close to the stations. Whereas in conventional tomography, a measurement made on a single earthquake-station pair provides very limited structural information, in double-difference tomography, one earthquake can actually resolve significant details of the structure. The double-difference methodology can be incorporated into the usual adjoint tomography workflow by simply pairing up all conventional measurements; the computational cost of the necessary adjoint simulations is largely unaffected. Rather than adding to the computational burden, the inversion of double-difference measurements merely modifies the construction of the adjoint sources for data assimilation.

  4. FET frequency discriminator

    Science.gov (United States)

    Mawhinney, F. D.

    1982-03-01

    The FET Frequency Discriminator is an experimental microwave frequency discriminator developed for use in a specialized set-on VCO frequency memory system. Additional development and evaluation work has been done during this program to more fully determine the applicability of the FET frequency discriminator as a low-cost, expendable receiver front-end for both surveillance and ECM systems. Various methods for adjusting the frequency-to-voltage characteristic of the discriminator as well as the effects of detector characteristics and ambient temperature changes were evaluated. A number of discriminators for use in the 7- to 11-GHz and the 11to 18-GHz bands were fabricated and tested. Interim breadboard and final packaged models were either delivered or installed in developmental frequency systems. The major limitations and deficiencies of the FET frequency discriminator that were reviewed during the program include the effects of temperature, input power level variations, nonlinearity, and component repeatability. Additional effort will be required to advance the developmental status of the FET frequency discriminator to the level necessary for inclusion in low-cost receiver systems, but the basic simplicity of the approach continues to show much promise.

  5. Frequency-agile antennas for wireless communications

    CERN Document Server

    Petosa, Aldo

    2013-01-01

    Mobile data subscriptions are expected to more than double and mobile wireless traffic to increase by more than tenfold over the next few years. Proliferation of smart phones, tablets, and other portable devices are placing greater demands for services such as web browsing, global positioning, video streaming, and video telephony. Many of the proposed solutions to deal with these demands will have a significant impact on antenna designs. Antennas with frequency agility are considered a promising technology to help implement these new solutions.This book provides readers with a sense of the cap

  6. Charge Transport in Resonant Tunneling Double - Diodes

    Science.gov (United States)

    Diff, Karim

    With the advent of semiconductor devices with typical lengths of the order of a few nanometers and response times of a few picoseconds, the conventional methods used in device modeling have reached their limits of validity. Modern devices based on heterostructures fabricated by Molecular Beam Epitaxy (MBE) require more fundamental approaches based entirely on quantum mechanics. These generally necessitate numerical solutions and are computationally intensive. This dissertation focuses on Resonant Tunneling Double-Barrier (RTDB) diodes as the prototype of "quantum devices". A one-electron model and the effective mass approximation are used. By solving numerically the time-dependent Schrodinger equation for Gaussian wavepackets, the various time characteristics of resonant tunneling are probed. These characteristics are usually overlooked in other treatments based on the time-independent Schrodinger equation. The transit time, the build-up time and the exponential decay time are studied. The difference between these various time scales and their relative importance are discussed. A new method that takes into account the finite extent of the electron wavefunction, is proposed to compute the I-V characteristics of such devices. Results indicate a possible explanation for the discrepancy observed between experimental results and previous analyses. The effect of high frequency fields on resonant tunneling is also studied, and a method to determine the intrinsic cut-off frequency is suggested. The role of the effective mass in the determination of the characteristics of RTDB diodes is emphasized throughout this work.

  7. A Design of Double Broadband MIMO Antenna

    Directory of Open Access Journals (Sweden)

    Yanfeng Geng

    2015-01-01

    Full Text Available The MIMO antenna applied to LTE mobile system should be miniaturization and can work in the current communication frequency band; isolation between each antenna unit also should be good so as to reduce loss of radio wave energy and improve the antenna performance of the MIMO system. This paper puts forward the design scheme of a broadband MIMO double antenna. And the design of antenna unit and debugging and related technical measures, such as bending antenna bracket, are both presented; the integration design of high isolation of ultra broadband MIMO antenna is realized on the plate with the volume of 100 × 52 × 0.8 mm3; antenna working bands are 698 MHz~960 MHz and 1710 MHz~2700 MHz; in the whole spectrum, the 10 dB of port isolation can be basically achieved; in low frequency band, the isolation degree of antenna port can reach 12 dB.

  8. Breakfast frequency among adolescents

    DEFF Research Database (Denmark)

    Pedersen, Trine Pagh; Holstein, Bjørn E; Damsgaard, Mogens Trab

    2016-01-01

    , quality of family communication and family support. Further, analyses suggested that the associations were more pronounced among girls, immigrants and adolescents from other family structure than traditional. The study highlights the importance of the family setting in promoting regular breakfast......OBJECTIVE: To investigate (i) associations between adolescents' frequency of breakfast and family functioning (close relations to parents, quality of family communication and family support) and (ii) if any observed associations between breakfast frequency and family functioning vary...... (n 3054) from a random sample of forty-one schools. RESULTS: Nearly one-quarter of the adolescents had low breakfast frequency. Low breakfast frequency was associated with low family functioning measured by three dimensions. The OR (95 % CI) of low breakfast frequency was 1·81 (1·40, 2...

  9. Double-tuned radiofrequency coil for (19)F and (1)H imaging.

    Science.gov (United States)

    Otake, Yosuke; Soutome, Yoshihisa; Hirata, Koji; Ochi, Hisaaki; Bito, Yoshitaka

    2014-01-01

    We developed a double-tuned radiofrequency (RF) coil using a novel circuit method to double tune for fluorine-19 (19F) and 1H magnetic resonance imaging, whose frequencies are very close to each other. The RF coil consists of 3 parallel-connected series inductor capacitor circuits. A computer simulation for our double-tuned RF coil with a phantom demonstrated that the coil has tuned resonant frequency and high sensitivity for both 19F and 1H. Drug distribution was visualized at 7 tesla using this RF coil and a rat administered perfluoro 15-crown-5-ether emulsion. The double-tune RF coil we developed may be a powerful tool for 19F and 1H imaging.

  10. Design studies for the Double Chooz trigger

    Energy Technology Data Exchange (ETDEWEB)

    Cucoanes, Andi Sebastian

    2009-07-24

    them receiving signals from half of the photomultipliers. A third trigger board will handle the inner veto signals and the additional trigger inputs. The work presented in this thesis establishes the trigger algorithm as result of the trigger efficiency optimization. The efficiency parameters are obtained from fits of Monte Carlo simulation data. Various possible influences are considered, the resulted algorithm being able to sustain the trigger goals for all kinds of events. Also presented is a method for measuring the trigger efficiency based on the redundancy of the two target trigger boards. Cosmogenic muons are the dominant source of the Double Chooz triggered events. For the near detector, the foreseen muon rate is {proportional_to}250 Hz. The DAQ system is unable to sustain the full read-out of the detector at such high frequency. As consequence, the triggered events are treated differently, regarding their importance for future analysis. For physics events, the full available information is saved, the offline data for background muons will contain only summary information. The trigger algorithm is able to identify ''special'' muons classes, for which the full detector read-out is performed. The muon recognition is based on the energy depositions from all detector regions and on the ''topological'' information provided by groups of inner veto photomultipliers. (orig.)

  11. An analysis of low frequency noise from large wind turbines

    DEFF Research Database (Denmark)

    Pedersen, Christian Sejer; Møller, Henrik

    2010-01-01

    between 75 kW and 3.6 MW was analyzed. The apparent sound power, LWA, increases with electric power at a rate close to 3 dB per doubling of electric power. The low-frequency proportion (10-160 Hz) increases more rapidly, and the difference in slope is statistically significant. A comparison of one-third-octave......As wind turbines get larger, worries have emerged, that the noise emitted by the turbines would move down in frequency, and that the contents of low-frequency noise would be enough to cause significant annoyance for the neighbors. The sound emission from 48 wind turbines with nominal electric power...

  12. Double field theory inspired cosmology

    Science.gov (United States)

    Wu, Houwen; Yang, Haitang

    2014-07-01

    Double field theory proposes a generalized spacetime action possessing manifest T-duality on the level of component fields. We calculate the cosmological solutions of double field theory with vanishing Kalb-Ramond field. It turns out that double field theory provides a more consistent way to construct cosmological solutions than the standard string cosmology. We construct solutions for vanishing and non-vanishing symmetry preserving dilaton potentials. The solutions assemble the pre- and post-big bang evolutions in one single line element. Our results show a smooth evolution from an anisotropic early stage to an isotropic phase without any special initial conditions in contrast to previous models. In addition, we demonstrate that the contraction of the dual space automatically leads to both an inflation phase and a decelerated expansion of the ordinary space during different evolution stages.

  13. Azeglio Bemporad and the "BEM" Double Stars

    Science.gov (United States)

    Smith, Steven; Prunotto, Marco

    2017-07-01

    This paper aims to describe the scientific context and the life of early 20th century Italian astronomer Azeglio Bemporad (1875-1945), his work on double stars, and how the “BEM” doubles were incorporated into the Washington Double Star catalog. Included are new measures, a complete photo gallery of all 61 of his double star systems, and copies of his double star publications.

  14. Double-Electromagnetically Induced Transparency in a Y-type atomic system

    CERN Document Server

    Safari, L; Fratini, F

    2013-01-01

    We study the absorption and dispersion properties of a weak tunable probe field in a four-level Y-type atomic system driven by two strong laser (coupling) fields within the framework of density matrix formalism. It is found that the probe absorption profile displays double-electromagnetically induced transparency (double-EIT) and it is shown how to control it by changing the Rabi frequencies as well as the atom field detuning of the coupling fields.

  15. Experimental observation of parametric effects near period doubling in a loss-modulated CO2 laser

    OpenAIRE

    Chizhevsky, V. N.; Corbalán, R.

    1996-01-01

    A number of parametric effects, such as suppression of period doubling, shift of the bifurcation point, scaling law relating the shift and the perturbation amplitude, influence of the detuning on the suppression, reaching of the maximum gain between the original and shifted bifurcation points, and scaling law for idler power are experimentally observed near period doubling bifurcation in a loss-driven CO2 laser that is subjected to periodic loss perturbations at a frequency that is close to a...

  16. Experimental observation of parametric effects near period doubling in a loss-modulated CO2 laser

    OpenAIRE

    Chizhevsky, V. N.; Corbalán, R.

    1996-01-01

    A number of parametric effects, such as suppression of period doubling, shift of the bifurcation point, scaling law relating the shift and the perturbation amplitude, influence of the detuning on the suppression, reaching of the maximum gain between the original and shifted bifurcation points, and scaling law for idler power are experimentally observed near period doubling bifurcation in a loss-driven CO2 laser that is subjected to periodic loss perturbations at a frequency that is close to a...

  17. Hybrid algorithm for accelerating the double series of Floquet vector modes

    Institute of Scientific and Technical Information of China (English)

    LI Weidong; HONG Wei; HAO Zhangcheng; ZHOU Houxing

    2006-01-01

    In this paper, a hybrid algorithm for accelerating the double series of Floquet vector modes arising in the analysis of frequency selective surfaces (FSS) is presented. The asymptotic terms with slow convergence in the double series are first accelerated by Poisson transformation and Ewald method, and then the remained series is accelerated by Shank transformation. It results in significant savings in memory and computing time. Numerical examples verify the validity of the hybrid acceleration algorithm.

  18. Magnetoresistance stories of double perovskites

    Indian Academy of Sciences (India)

    Abhishek Nag; Sugata Ray

    2015-06-01

    Tunnelling magnetoresistance (TMR) in polycrystalline double perovskites has been an important research topic for more than a decade now, where the nature of the insulating tunnel barrier is the core issue of debate. Other than the nonmagnetic grain boundaries as conventional tunnel barriers, intragrain magnetic antiphase boundaries (APB) as well as magnetically frustrated grain surfaces have also been proposed to act as tunnel barriers in Sr2FeMoO6. In this review, the present state of the debate has been discussed briefly and how the physical state of the material can affect the magnetoresistance signal of double perovskites in many different ways has been pointed out.

  19. Attosecond double-slit experiment.

    Science.gov (United States)

    Lindner, F; Schätzel, M G; Walther, H; Baltuska, A; Goulielmakis, E; Krausz, F; Milosević, D B; Bauer, D; Becker, W; Paulus, G G

    2005-07-22

    A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (slits) of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are measured. A situation in which one and the same electron encounters a single and a double slit at the same time is observed. The investigation of the fringes makes possible interferometry on the attosecond time scale. From the number of visible fringes, for example, one derives that the slits are extended over about 500 as.

  20. Quasisymmetric functions and Heisenberg doubles

    Directory of Open Access Journals (Sweden)

    Jie Sun

    2016-09-01

    Full Text Available The ring of quasisymmetric functions is free over the ring of symmetric functions. This result waspreviously proved by M. Hazewinkel combinatorially through constructing a polynomial basis forquasisymmetric functions. The recent work by A. Savage and O. Yacobi on representation theoryprovides a new proof to this result. In this paper, we proved that under certain conditions, thepositive part of a Heisenberg double is free over the positive part of the corresponding projectiveHeisenberg double. Examples satisfying the above conditions are discussed.

  1. Neutrinoless double beta decay experiments

    CERN Document Server

    Zuber, K

    2006-01-01

    The study of neutrinoless double beta decay is of outmost importance for neutrino physics. It is considered to be the gold plated channel to probe the fundamental character of neutrinos and to determine the neutrino mass. From the experimental point about nine different isotopes are explored for the search. After a general introduction follows a short discussion on nuclear matrix element calculations and supportive measurements. The current experimental status of double beta searches is presented followed by a short discussion of the ideas and proposals for large scale experiments.

  2. DOUBLE-MARKOV RISK MODEL

    Institute of Scientific and Technical Information of China (English)

    Xiaoyun MO; Jieming ZHOU; Hui OU; Xiangqun YANG

    2013-01-01

    Given a new Double-Markov risk model DM =(μ,Q,v,H; Y,Z) and Double-Markov risk process U ={U(t),t ≥ 0}.The ruin or survival problem is addressed.Equations which the survival probability satisfied and the formulas of calculating survival probability are obtained.Recursion formulas of calculating the survival probability and analytic expression of recursion items are obtained.The conclusions are expressed by Q matrix for a Markov chain and transition probabilities for another Markov Chain.

  3. Double stranded nucleic acid biochips

    Energy Technology Data Exchange (ETDEWEB)

    Chernov, Boris; Golova, Julia

    2006-05-23

    This invention describes a new method of constructing double-stranded DNA (dsDNA) microarrays based on the use of pre-synthesized or natural DNA duplexes without a stem-loop structure. The complementary oligonucleotide chains are bonded together by a novel connector that includes a linker for immobilization on a matrix. A non-enzymatic method for synthesizing double-stranded nucleic acids with this novel connector enables the construction of inexpensive and robust dsDNA/dsRNA microarrays. DNA-DNA and DNA-protein interactions are investigated using the microarrays.

  4. Membongkar Akuntansi Double Entry Systems

    Directory of Open Access Journals (Sweden)

    Whedy Prasetyo

    2013-08-01

    Full Text Available Double entry isa process of recording transactions that always involve at least two accounts ofwhich changes (increases or decreases have consequences to maintain a balance equation. This is a simple basic accounting, that the use of the funds must alwaysbe equal to the acquisition of funds. The equation is not able to include some business events that are responses to the development of business environment. A proposed view is based on the interaction of researcher (New Bond with accountant (Mrs M to dismantle the double entry accounting through Maurice Merleau Ponty's approach (1906-1961. The results prove that physical aspects of knowledge willcontinue to evolve according to environmental interactions.

  5. Topics in Double Field Theory

    Science.gov (United States)

    Kwak, Seung Ki

    The existence of momentum and winding modes of closed string on a torus leads to a natural idea that the field theoretical approach of string theory should involve winding type coordinates as well as the usual space-time coordinates. Recently developed double field theory is motivated from this idea and it implements T-duality manifestly by doubling the coordinates. In this thesis we will mainly focus on the double field theory formulation of different string theories in its low energy limit: bosonic, heterotic, type II and its massive extensions, and N = 1 supergravity theory. In chapter 2 of the thesis we study the equivalence of different formulations of double field theory. There are three different formulations of double field theory: background field E formulation, generalized metric H formulation, and frame field EAM formulation. Starting from the frame field formalism and choosing an appropriate gauge, the equivalence of the three formulations of bosonic theory are explicitly verified. In chapter 3 we construct the double field theory formulation of heterotic strings. The global symmetry enlarges to O( D, D + n) for heterotic strings and the enlarged generalized metric features this symmetry. The structural form of bosonic theory can directly be applied to the heterotic theory with the enlarged generalized metric. In chapter 4 we develop a unified framework of double field theory for type II theories. The Ramond-Ramond potentials fit into spinor representations of the duality group O( D, D) and the theory displays Spin+( D, D) symmetry with its self-duality relation. For a specific form of RR 1-form the theory reduces to the massive deformation of type IIA theory due to Romans. In chapter 5 we formulate the N = 1 supersymmetric extension of double field theory including the coupling to n abelian vector multiplets. This theory features a local O(1, 9 + n) x O(1, 9) tangent space symmetry under which the fermions transform. (Copies available exclusively from

  6. Present and Future Modes of Low Frequency Climate Variability

    Energy Technology Data Exchange (ETDEWEB)

    Cane, Mark A.

    2014-02-20

    This project addressed area (1) of the FOA, “Interaction of Climate Change and Low Frequency Modes of Natural Climate Variability”. Our overarching objective is to detect, describe and understand the changes in low frequency variability between model simulations of the preindustrial climate and simulations of a doubled CO2 climate. The deliverables are a set of papers providing a dynamical characterization of interannual, decadal, and multidecadal variability in coupled models with attention to the changes in this low frequency variability between pre-industrial concentrations of greenhouse gases and a doubling of atmospheric concentrations of CO2. The principle mode of analysis, singular vector decomposition, is designed to advance our physical, mechanistic understanding. This study will include external natural variability due to solar and volcanic aerosol variations as well as variability internal to the climate system. An important byproduct is a set of analysis tools for estimating global singular vector structures from the archived output of model simulations.

  7. Frequency comb swept lasers.

    Science.gov (United States)

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G

    2009-11-09

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

  8. Single-balloon versus double-balloon bipedicular kyphoplasty for osteoporotic vertebral compression fractures.

    Science.gov (United States)

    Wang, Heng; Sun, Zhenzhong; Wang, Zhiwen; Jiang, Weimin

    2015-04-01

    Twenty-eight patients with osteoporotic vertebral compression fractures (OVCF) were treated with single-balloon bipedicular kyphoplasty (Group A), and 40 patients were treated with double-balloon bipedicular kyphoplasty (Group B). Visual Analogue Scale (VAS) score, vertebral height, and kyphotic angle (KA) were evaluated pre-operatively, post-operatively (3 days after surgery) and at final follow-up. Operative time, X-ray exposure frequency and costs were recorded. The mean operative time and X-ray exposure frequency in Group A were greater than in Group B (pkyphoplasty is a safe and cost-effective surgical method for the treatment of OVCF. It can achieve pain relief comparable with double-balloon bipedicular kyphoplasty. However, double-balloon bipedicular kyphoplasty is more efficacious in terms of the restoration of vertebral height and reduction of KA, and the operative time and X-ray exposure frequency are lower.

  9. Tolerance of Whole-Genome Doubling Propagates Chromosomal Instability and Accelerates Cancer Genome Evolution

    DEFF Research Database (Denmark)

    Dewhurst, Sally M.; McGranahan, Nicholas; Burrell, Rebecca A.;

    2014-01-01

    The contribution of whole-genome doubling to chromosomal instability (CIN) and tumor evolution is unclear. We use long-term culture of isogenic tetraploid cells from a stable diploid colon cancer progenitor to investigate how a genome-doubling event affects genome stability over time. Rare cells...... that survive genome doubling demonstrate increased tolerance to chromosome aberrations. Tetraploid cells do not exhibit increased frequencies of structural or numerical CIN per chromosome. However, the tolerant phenotype in tetraploid cells, coupled with a doubling of chromosome aberrations per cell, allows...... chromosome abnormalities to evolve specifically in tetraploids, recapitulating chromosomal changes in genomically complex colorectal tumors. Finally, a genome-doubling event is independently predictive of poor relapse-free survival in early-stage disease in two independent cohorts in multivariate analyses...

  10. Quantum frequency downconversion experiment

    CERN Document Server

    Takesue, Hiroki

    2010-01-01

    We report the first quantum frequency downconversion experiment. Using the difference frequency generation process in a periodically poled lithium niobate waveguide, we successfully observed the phase-preserved frequency downconversion of a coherent pulse train with an average photon number per pulse of $<$1, from the 0.7-$\\mu$m visible wavelength band to the 1.3-$\\mu$m telecom band. We expect this technology to become an important tool for flexible photonic quantum networking, including the realization of quantum repeater systems over optical fiber using atom-photon entanglement sources for the visible wavelength bands.

  11. Pragmatic circuits frequency domain

    CERN Document Server

    Eccles, William

    2006-01-01

    Pragmatic Circuits: Frequency Domain goes through the Laplace transform to get from the time domain to topics that include the s-plane, Bode diagrams, and the sinusoidal steady state. This second of three volumes ends with a-c power, which, although it is just a special case of the sinusoidal steady state, is an important topic with unique techniques and terminology. Pragmatic Circuits: Frequency Domain is focused on the frequency domain. In other words, time will no longer be the independent variable in our analysis. The two other volumes in the Pragmatic Circuits series include titles on DC

  12. Influence of mating frequency on sow reproductive performance.

    Science.gov (United States)

    Xue, J; Dial, G D; Trigg, T; Davies, P; King, V L

    1998-12-01

    Gilts and sows were bred one, two, or three times during a single estrous period in a commercial herd for evaluating the effect of mating frequency on reproductive performance. Estrus detection started at approximately 0630 daily by applying back pressure to females with the presence of a mature boar. Natural mating was used. Gilts detected in estrus were mated in the morning of d 1 (AM), the morning of d 1 and 2 (AM-AM), and the morning and afternoon of d 1 and morning of d 2 (AM-PM-AM) for mating frequencies 1, 2, and 3, respectively. Sows were bred in the AM, AM-AM, AM-PM-AM (1), and morning of d 1 and morning and afternoon of d 2 [AM-AM-PM (2)] for mating frequency 1, 2, 3 (1), and 3 (2), respectively. Breeding events in the morning and afternoon started at approximately 0730 and 1530. Females were randomly assigned to a mating frequency. Boars were randomly assigned to each breeding event. In total, 256 gilts and 766 sows were involved in the study. Gilts with a single mating (76.5%, P = .06) and triple matings (80.4%, P .1) in the farrowing rates of sows were observed between mating frequencies 1, 2, 3 (1), and 3 (2). Double-mated gilts had more (P .3) in total born and pigs born alive in sows between mating frequencies. We concluded that triple-mating gilts and sows did not improve farrowing rate and litter size compared with single and double matings. There were no differences in farrowing rate and litter size between double- and single-mated sows. Gilts with double matings had a larger litter size than those with a single mating.

  13. Generation and storage of double slow light pulses in a solid

    Institute of Scientific and Technical Information of China (English)

    Fan Yun-Fei; Wang Hai-Hua; Wang Rong; Zhang Xiao-Jun; Kang Zhi-Hui; Wu Jin-Hui; Zhang Han-Zhuang; Gao Jin-Yue

    2012-01-01

    We experimentally study the generation and storage of double slow light pulses in a Pr3+:Y2SiO5 crystal.Under electromagnetically induced transparency,a single signal pulse is stored in the spin coherence of the crystal. By simultaneously switching on two control fields to recall the stored information,the spin coherence is converted into two slow light pulses with distinct frequencies.Furthermore,the storage and controlled retrieval of double slow light pulses are obtained by manipulating the control fields.This study of double slow light pulses may have practical applications in information processing and all-optical networks.

  14. Modelling the nonlinear behaviour of double walled carbon nanotube based resonator with curvature factors

    Science.gov (United States)

    Patel, Ajay M.; Joshi, Anand Y.

    2016-10-01

    This paper deals with the nonlinear vibration analysis of a double walled carbon nanotube based mass sensor with curvature factor or waviness, which is doubly clamped at a source and a drain. Nonlinear vibrational behaviour of a double-walled carbon nanotube excited harmonically near its primary resonance is considered. The double walled carbon nanotube is harmonically excited by the addition of an excitation force. The modelling involves stretching of the mid plane and damping as per phenomenon. The equation of motion involves four nonlinear terms for inner and outer tubes of DWCNT due to the curved geometry and the stretching of the central plane due to the boundary conditions. The vibrational behaviour of the double walled carbon nanotube with different surface deviations along its axis is analyzed in the context of the time response, Poincaré maps and Fast Fourier Transformation diagrams. The appearance of instability and chaos in the dynamic response is observed as the curvature factor on double walled carbon nanotube is changed. The phenomenon of Periodic doubling and intermittency are observed as the pathway to chaos. The regions of periodic, sub-harmonic and chaotic behaviour are clearly seen to be dependent on added mass and the curvature factors in the double walled carbon nanotube. Poincaré maps and frequency spectra are used to explicate and to demonstrate the miscellany of the system behaviour. With the increase in the curvature factor system excitations increases and results in an increase of the vibration amplitude with reduction in excitation frequency.

  15. Pure Electric and Pure Magnetic Resonances in Near-Infrared Metal Double-Triangle Metamaterial Arrays

    Institute of Scientific and Technical Information of China (English)

    CAO Zhi-Shen; PAN Jian; CHEN Zhuo; ZHAN Peng; MIN Nai-Ben; WANG Zhen-Lin

    2011-01-01

    @@ We experimentally and numerically investigate the optical properties of metamaterial arrays composed of double partially-overlapped metallic nanotriangles fabricated by an angle-resolved nanosphere lithography.We demonstrate that each double-triangle can be viewed as an artificial magnetic element analogous to the conventional metal split-ring-resonator.It is shown that under normal-incidence conditions,individual double-triangle can exhibit a strong local magnetic resonance,but the collective response of the metamaterial arrays is purely electric because magnetic resonances of the two double-triangles in a unit cell having opposite openings are out of phase.For oblique incidences the metamaterial arrays are shown to support a pure magnetic response at the same frequency band.Therefore,switchable electric and magnetic resonances are achieved in double-triangle arrays.Moreover,both the electric and magnetic resonances axe shown to allow for a tunability over a large spectral range down to near-infrared.%We experimentally and numerically investigate the optical properties of metamaterial arrays composed of double partially-overlapped metallic nanotriangles fabricated by an angle-resolved nanosphere lithography. We demonstrate that each double-triable can be viewed as an artificial magnetic element analogous to the conventional metal split-ring-resonator. It is shown that under normal-incidence conditions, individual double-triangle can exhibit a strong local magnetic resonance, but the collective response of the metamaterial arrays is purely electric because magnetic resonances of the two double-triangles in a unit cell having opposite openings are out of phase.For oblique incidences the metamaterial arrays are shown to support a pure magnetic response at the same frequency band. Therefore, switchable electric and magnetic resonances are achieved in double-triangle arrays.Moreover, both the electric and magnetic resonances are shown to allow for a tunability over

  16. Double Star Mission Starts Countdown

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    @@ As of July, scientists at the CAS Center for Space Science and Applied Research (CSSAR) have been busy modulating and testing the payloads that will be onboard a space exploration satellite, marking the start of the countdown for China's Double Star Project.

  17. Some Alternating Double Binomial Sums

    Institute of Scientific and Technical Information of China (English)

    ZHENG De-yin; TANG Pei-pei

    2013-01-01

    We consider some new alternating double binomial sums. By using the Lagrange inversion formula, we obtain explicit expressions of the desired results which are related to a third-order linear recursive sequence. Furthermore, their recursive relation and generating functions are obtained.

  18. On neutrinoless double electron capture

    CERN Document Server

    Drukarev, E G

    2016-01-01

    We found the probability for the neutrinoless double electron capture in the case of $KK$ capture. We clarified the mechanism of the energy transfer from the nucleus to the bound electrons. This enabled us to obtain the equations for the probability of the $2EC0\

  19. Doubled-ended ceramic thyratron

    CERN Multimedia

    1974-01-01

    The double-ended ceramic thyratron CX 1171 B, with its coaxial voltage divider for the SPS. Such a switch, paralleled by three ignitrons in series forms the "thyragnitron" arrangement, and can switch 10 kA, 25 ms pulses, with very fast rise times.

  20. Double emulsions as fat replacers

    NARCIS (Netherlands)

    Oppermann, Anika

    2017-01-01

    The use of double (w1/o/w2) emulsions, in which part of the oil is replaced by small water droplets, is a promising strategy to reduce oil content in food products. For successful applications, (1) significant levels of fat reduction (i.e. significant amounts of water inside the oil droplets) have

  1. A Double-Minded Fractal

    Science.gov (United States)

    Simoson, Andrew J.

    2009-01-01

    This article presents a fun activity of generating a double-minded fractal image for a linear algebra class once the idea of rotation and scaling matrices are introduced. In particular the fractal flip-flops between two words, depending on the level at which the image is viewed. (Contains 5 figures.)

  2. On double bonds in fullerenes

    Directory of Open Access Journals (Sweden)

    Stepenshchikov D. G.

    2016-03-01

    Full Text Available Various distributions of double carbon bonds in the fullerenes have been considered in the paper from the point that they are absent in the pentagonal rings. The appropriate classification of the fullerenes has been built. The results may be used when modeling the fullerenes of a given topology and calculating their physical-chemical properties

  3. Double Coffee opens in China

    Index Scriptorium Estoniae

    2009-01-01

    Läti suursaadik Ingrida Levrence avas esimese Double Coffee kohviku Hiina pealinnas Pekingi südames. Rahvusvaheline kohvikukett kavatseb laieneda mõne kohviku võrra igal aastal. Seni tegutsetakse Lätis, Eestis, Leedus, Ukrainas ja Valgevenes

  4. Double Photoionization of Atomic Oxygen

    Science.gov (United States)

    Wickramarathna, Madhushani; Gorczyca, Thomas; Ballance, Connor; Stolte, Wayne

    2016-05-01

    Double photoionization of atomic oxygen was first measured at Aladdin, a second-generation synchrotron source, at lower resolution (Angel and Samson, PRA, 38, 5573, 1988). Here we present new experimental and theoretical results for the direct double photoionization of atomic oxygen. The experiment was performed at the Advanced Light Source for photon energies near the double-ionization threshold, revealing rich resonance structures converging to multiple single-ionization thresholds. State-of-the-art calculations were performed using the R-matrix with pseudostates (RMPS) method (P. G. Burke, R-matrix Theory of Atomic Collisions, Springer 2011) as implemented by Gorczya and Badnell (JPB, 30, 3897, 1997), and recently applied, in a converged representation, to the double photoionization of helium (T. W. Gorczyca et al., JPB, 46, 195201, 2013). The much-larger calculation required for oxygen, due to the many target state symmetries compared to helium, necessitated a parallel RMPS approach. Comparison between theoretical and experimental results shows overall qualitative agreement but also some puzzling discrepancies: experimental features that are not reproduced by the RMPS calculations.

  5. Relics of Double Radio Sources

    CERN Document Server

    Dwarakanath, K S

    2009-01-01

    We have formed a new sample which consists of extended extragalactic radio sources without obvious active galactic nuclei (AGN) in them. Most of these sources appear to be dead double radio sources. These sources with steep spectra ($\\alpha < $ -1.8; S $\\propto \

  6. Double Coffee opens in China

    Index Scriptorium Estoniae

    2009-01-01

    Läti suursaadik Ingrida Levrence avas esimese Double Coffee kohviku Hiina pealinnas Pekingi südames. Rahvusvaheline kohvikukett kavatseb laieneda mõne kohviku võrra igal aastal. Seni tegutsetakse Lätis, Eestis, Leedus, Ukrainas ja Valgevenes

  7. Eight Arguments against Double Effect

    DEFF Research Database (Denmark)

    Di Nucci, Ezio

    I offer eight arguments against the Doctrine of Double Effect, a normative principle according to which in pursuing the good it is sometimes morally permissible to bring about some evil as a side-effect or merely foreseen consequence: the same evil would not be morally justified as an intended...

  8. Raman Spectra Of Double-Walled Carbon Nanotubes

    Science.gov (United States)

    Vuković, T.; Dmitrović, S.; Dobardžić, E.

    2007-04-01

    Using nonresonant bond-polarization theory, Raman spectra of periodic double-walled carbon nanotubes (DWCNTs) are calculated. Due to the lower symmetry of DWCNT, the number of Raman active modes is much larger compared to those of its layers. Complete frequency range of the tubes spectra has been analyzed for large number of tubes. We found that only modes whose frequencies are below 800 cm-1 have noticeable up shifts compared to those of isolated layers. Special attention is given to radial breathing modes (RBMs) and G-band region since these modes are used for the identification of singe-walled carbon nanotubes. In case of breathing like modes (BLMs), frequency of the out of phase mode is found to be chirality dependent, while the in phase one remains only diameter dependent as in the case of individual layers.

  9. Single frequency semiconductor lasers

    CERN Document Server

    Fang, Zujie; Chen, Gaoting; Qu, Ronghui

    2017-01-01

    This book systematically introduces the single frequency semiconductor laser, which is widely used in many vital advanced technologies, such as the laser cooling of atoms and atomic clock, high-precision measurements and spectroscopy, coherent optical communications, and advanced optical sensors. It presents both the fundamentals and characteristics of semiconductor lasers, including basic F-P structure and monolithic integrated structures; interprets laser noises and their measurements; and explains mechanisms and technologies relating to the main aspects of single frequency lasers, including external cavity lasers, frequency stabilization technologies, frequency sweeping, optical phase locked loops, and so on. It paints a clear, physical picture of related technologies and reviews new developments in the field as well. It will be a useful reference to graduate students, researchers, and engineers in the field.

  10. Microwave Radiometer - high frequency

    Data.gov (United States)

    Oak Ridge National Laboratory — The Microwave Radiometer-High Frequency (MWRHF) provides time-series measurements of brightness temperatures from two channels centered at 90 and 150 GHz. These two...

  11. Keepers of the double stars

    Science.gov (United States)

    Tenn, Joseph S.

    2013-03-01

    Astronomers have long tracked double stars in efforts to find those that are gravitationally-bound binaries and then to determine their orbits. Early catalogues by the Herschels, Struves, and others began with their own discoveries. In 1906 court reporter and amateur astronomer Sherburne Wesley Burnham published a massive double star catalogue containing data from many observers on more than 13,000 systems. Lick Observatory astronomer Robert Grant Aitken produced a much larger catalogue in 1932 and coordinated with Robert Innes of Johannesburg, who catalogued the southern systems. Aitken maintained and expanded Burnham's records of observations on handwritten file cards, and eventually turned them over to the Lick Observatory, where astrometrist Hamilton Jeffers further expanded the collection and put all the observations on punched cards. With the aid of Frances M. "Rete" Greeby he made two catalogues: an Index Catalogue with basic data about each star, and a complete catalogue of observations, with one observation per punched card. He enlisted Willem van den Bos of Johannesburg to add southern stars, and together they published the Index Catalogue of Visual Double Stars, 1961.0. As Jeffers approached retirement he became greatly concerned about the disposition of the catalogues. He wanted to be replaced by another "double star man," but Lick Director Albert E. Whitford had the new 120-inch reflector, the world's second largest telescope, and he wanted to pursue modern astrophysics instead. Jeffers was vociferously opposed to turning over the card files to another institution, and especially against their coming under the control of Kaj Strand of the United States Naval Observatory. In the end the USNO got the files and has maintained the records ever since, first under Charles Worley, and, since 1997, under Brian Mason. Now called the Washington Double Star Catalog (WDS), it is completely online and currently contains more than 1,200,000 measures of more than 125

  12. Nonlinear dynamics and load sharing of double-mesh helical gear train

    Directory of Open Access Journals (Sweden)

    Fuchun Yang

    2013-07-01

    Full Text Available Dynamic behaviours and load sharing of double-mesh helical gear trains have been studied in this paper. A nonlinear dynamic model of double-mesh helical gear train was established, including torsional vibration, axial vibration, timevarying mesh stiffness and backlashes. The governing equations were solved by Runge-Kutta method. Frequency responses and influences of main parameters to frequency responses were analyzed to determine the vibration characteristics of the system. The dynamic factor and load sharing in two mesh pairs were studied in two configuration cases and the result shows that case II has better dynamic response and load sharing.

  13. Automatic Segmentation for Reach/frequency Estimation of Newspaper Sections and Internet Papers

    DEFF Research Database (Denmark)

    Mortensen, Peter Stendahl; Arnaa, Kristian

    1999-01-01

    This paper will present a new way of estimating reach and frequency without asking the frequency question or conducting double interviewing. Instead, the sample is segmented automatically by a CHAID-analysis, maximising the differences in reading probabilities among the segments. Typically, many ...

  14. Study on the dynamic performance of a novel buck-boost matrix converter based on double-loop control strategy

    Science.gov (United States)

    Li, Qing; Zhang, Xiao-ping; Chen, Qi

    2011-12-01

    The dynamic performance of a novel Buck-Boost matrix converter (BBMC) based on double-loop control strategy is put forward in this paper. The fundamental principle of BBMC has been elaborated and the method of the double-loop control strategy has been built with Matlab, and then the dynamic performances of BBMC based on the double-loop control strategy are discussed. The results show that the output voltage and frequency can be almost constant with the BBMC and double-loop control strategy despite of the changeable input voltage and frequency. Moreover, a high-quality sine output wave with low harmonic distortion can be directly obtained without filtering. So it can be drawn that the BBMC based on the double-loop control strategy has perfectly dynamic performance and practical importance to the engineering.

  15. Application of the blue-on-yellow perimetry with visual electrophysiological tests on the early diagnosis of primary open angle glaucoma%蓝黄视野联合图形视觉电生理检查在原发性开角型青光眼早期诊断中应用

    Institute of Scientific and Technical Information of China (English)

    海鸥; 安洁

    2016-01-01

    Objective To evaluate the clinical value of blue-on-yellow perimetry combined with visual electrophysiology on the early diagnosis of primary open angle glaucoma. Methods Thirty-six(fifty-two eyes) suspected open angle glaucoma served as SOAG group,and thirty-two ( fifty-four eyes) normal subjects served as control group. B/Y P, P-ERG and P-VEP were examined in two groups. Results (1)The mean sensitivity of SOAG group and control group were(16. 39 ± 3. 26) dB and(21. 65 ± 2. 14) dB,there was a significant difference between two groups(t=3. 62,P<0. 01). The mean defect of SOAG group and control group were(4. 32 ± 2. 18) dB and(2. 85 ±1. 83) dB,there was a significant difference between two groups(t=2. 45,P<0. 05). (2)The amplitude and latency of N95 in SOAG group were(8. 16 ± 2. 53) μV and(96. 75 ± 11. 29) ms,and the amplitude and latency of N95 in control groupwere(9.82±2.25) μVand(91.43±9.63) ms.Therewasalsosignificantdifferenceinboththeamplitudeandlatency(t=4. 69,t=3. 15,P<0. 01). (3)The amplitude and latency of P100 in SOAG group were(8. 73 ± 2. 54) μV and(102. 36 ± 3. 29) ms, the amplitude and latency of P100 in control group were(10. 58 ± 2. 26) μV and(98. 28 ± 2. 75) ms. There was significant difference in the amplitude and latency(t=3. 48,2. 24,P<0. 05). Conclusion Blue-on-yellow perimetry combined with the electrophysiologi-cal tests can be used in the early diagnosis of primary open-angle glaucoma.%目的:探讨蓝黄视野和图形视觉电生理检查在原发性开角型青光眼早期诊断中的敏感性,为临床早期诊断提供依据。方法选择36例(52眼)可疑青光眼患者和32例(54眼)正常对照者进行蓝黄视野(B/YP)、图形视网膜点图(P-ERG)和图形视网膜诱发电位( P-VEP)检查。 B/YP采用Humphrey-750型全自动电脑视野计进行检查,P-ERG和P-VEP采用RE-TIscan和RETI-port视觉电生理检查系统进行检测。结果(1)可疑青光眼组中全视网膜光敏度均值为(16.39±3.26) d

  16. Pathways to doubled haploidy: chromosome doubling during androgenesis.

    Science.gov (United States)

    Seguí-Simarro, J M; Nuez, F

    2008-01-01

    Production of doubled haploid (DH) plants through androgenesis induction is a promising and convenient alternative to conventional selfing techniques for the generation of pure lines for breeding programs. This process comprises two main steps: induction of androgenesis and duplication of the haploid genome. Such duplication is sometimes indirectly induced by the treatments used to promote androgenic development. But usually, an additional step of direct chromosome doubling must be included in the protocol. Duplication of the haploid genome of androgenic individuals has been thought to occur through three mechanisms: endoreduplication, nuclear fusion and c-mitosis. In this review we will revise and analyze the evidences supporting each of the proposed mechanisms and their relevance during androgenesis induction, embryo/callus development and plant regeneration. Special attention will be devoted to nuclear fusion, whose evidences are accumulating in the last years.

  17. Thermo-electric transports in double-Weyl semimetals

    Science.gov (United States)

    Chen, Qi; Fiete, Gregory A.

    Topological Weyl semimetals with linearly dispersing nodal points have received a surge of interest due to their experimental realization in real materials. Another nontrivial type of band crossing whose dispersion is not simply linear is the double Weyl point, around which the spectrum disperses linearly along one momentum direction but quadratically along the two remaining directions. In this work, we apply the semi-classical Boltzmann transport theory to study the thermo-electric conductivity of a double-Weyl fermion model. We find that the transport quantities exhibit an interesting dependence on the chemical potential and spatial anisotropic model parameters, differing from a simple quadratically or linearly dispersing electron gas. By applying a static magnetic field, we find that the double-Weyl point is only stable for a magnetic field along the linearly dispersing direction. The longitudinal and transverse electrical and thermal magneto-conductivity show a similar dependence on the in-plane cyclotron frequency to the linearly dispersing Weyl nodes. In the extreme quantum limit of chemical potential being much smaller than the cyclotron energy, we find that the lowest Landau levels are both chiral and doubly degenerate. The chiral anomaly contribution to the longitudinal magneto-conductivity is double that of a linearly dispersing Weyl node.

  18. Vibro-Shock Dynamics Analysis of a Tandem Low Frequency Resonator-High Frequency Piezoelectric Energy Harvester.

    Science.gov (United States)

    Žižys, Darius; Gaidys, Rimvydas; Ostaševičius, Vytautas; Narijauskaitė, Birutė

    2017-04-27

    Frequency up-conversion is a promising technique for energy harvesting in low frequency environments. In this approach, abundantly available environmental motion energy is absorbed by a Low Frequency Resonator (LFR) which transfers it to a high frequency Piezoelectric Vibration Energy Harvester (PVEH) via impact or magnetic coupling. As a result, a decaying alternating output signal is produced, that can later be collected using a battery or be transferred directly to the electric load. The paper reports an impact-coupled frequency up-converting tandem setup with different LFR to PVEH natural frequency ratios and varying contact point location along the length of the harvester. RMS power output of different frequency up-converting tandems with optimal resistive values was found from the transient analysis revealing a strong relation between power output and LFR-PVEH natural frequency ratio as well as impact point location. Simulations revealed that higher power output is obtained from a higher natural frequency ratio between LFR and PVEH, an increase of power output by one order of magnitude for a doubled natural frequency ratio and up to 150% difference in power output from different impact point locations. The theoretical results were experimentally verified.

  19. Double layers and double wells in arbitrary degenerate plasmas

    Science.gov (United States)

    Akbari-Moghanjoughi, M.

    2016-06-01

    Using the generalized hydrodynamic model, the possibility of variety of large amplitude nonlinear excitations is examined in electron-ion plasma with arbitrary electron degeneracy considering also the ion temperature effect. A new energy-density relation is proposed for plasmas with arbitrary electron degeneracy which reduces to the classical Boltzmann and quantum Thomas-Fermi counterparts in the extreme limits. The pseudopotential method is employed to find the criteria for existence of nonlinear structures such as solitons, periodic nonlinear structures, and double-layers for different cases of adiabatic and isothermal ion fluids for a whole range of normalized electron chemical potential, η0, ranging from dilute classical to completely degenerate electron fluids. It is observed that there is a Mach-speed gap in which no large amplitude localized or periodic nonlinear excitations can propagate in the plasma under consideration. It is further revealed that the plasma under investigation supports propagation of double-wells and double-layers the chemical potential and Mach number ranges of which are studied in terms of other plasma parameters. The Mach number criteria for nonlinear waves are shown to significantly differ for cases of classical with η0 0 regimes. It is also shown that the localized structure propagation criteria possess significant dissimilarities for plasmas with adiabatic and isothermal ions. Current research may be generalized to study the nonlinear structures in plasma containing positrons, multiple ions with different charge states, and charged dust grains.

  20. Term frequency inverse document frequency (TF-IDF) technique and ...

    African Journals Online (AJOL)

    Term frequency inverse document frequency (TF-IDF) technique and artificial neural ... AFRICAN JOURNALS ONLINE (AJOL) · Journals · Advanced Search · USING AJOL ... Electronic mail contents are extracted and Term Frequency Inverse ...