New technique to measure the cavity defects of Fabry–Perot interferometers

Context. Several astronomical instruments, for both nighttime and solar use, rely on tunable Fabry–Perot interferometers (FPIs). Knowing the exact shape of the etalons’ cavity is crucial for assessing the overall instrumental transmission profile and its possible variations during the tuning process. Aims. We aim to define and test a technique to accurately measure the cavity defects of air-spaced FPIs, including distortions due to the spectral tuning process that are typical of astronomical observations. We further aim to develop a correction technique to maintain the shape of the cavity as constant as possible during the spectral scan. These are necessary steps to optimize the spectral transmission profile of a two-dimensional spectrograph (polarimeter) using one or more FPIs in series, and to ensure that the spectral transmission profile remains constant during typical observing conditions. Methods. We devised a generalization of the techniques developed for the so-called phase-shifting interferometry to the case of FPI. This measuring technique is applicable to any given FPI that can be tuned via changing the cavity spacing (z-axis), and can be used for any etalon regardless of the coating’ reflectivity. The major strength of our method is the ability to fully characterize the cavity during a spectral scan, allowing for the determination of scan-dependent modifications of the plates. We have applied the measuring technique to three 50 mm diameter interferometers, with cavity gaps ranging between 600 μm and 3 mm, coated for use in the visible range. Results. The technique developed in this paper allows us to accurately and reliably measure the cavity defects of air-spaced FPIs, and of their evolution during the entire spectral scan. Our main, and unexpected, result is that the relative tilt between the two FPI plates varies significantly during the spectral scan, and can dominate the cavity defects; in particular, we observe that the tilt component at the extremes of the scan is sensibly larger than that at the center of the scan. Exploiting the capability of the electronic controllers to set the reference plane at any given spectral step, we then develop a correction technique that allows the minimization of the tilt during a complete spectral scan. The correction remains highly stable over long periods, well beyond the typical duration of astronomical observations.

Novel prognostic biomarkers and their association with survival in pancreatic cancers.

296 Background: Early detection of pancreatic cancer would allow for improved survival outcomes. Methods: We retrospectively evaluated serum protease levels and the survival of 15 pancreatic cancer patient samples (6 localized and 9 metastatic) at the KU Cancer Center. Available serum protease assays measured matrix metalloproteinases (MMPs), urokinase plasminogen activator (uPA), arginase, neutrophil elastase (NE), cathepsin B (CTSB) and cathepsin E (CTSE). The assays utilize fluorescent nanoparticle-based nanobiosensors which increase fluorescence upon posttranslational modification or enzymatic cleavage of targeted compounds and were read by a Spectral scan plate reader. Survival analysis was performed using Kaplan-Meier methods. Results: Baseline characteristics for all 15 patients are in (Table). Median OS was 18.8m in patients with high CTSB expression (mean >51968.9) vs 9.7m in low CTSB expression (p=0.04). Similarly, median OS was 20.4m in high CTSE expression (>123264.8) vs 10m in low CTSE expression (p=0.05). Whereas, median OS was 16.3m in low NE expression (mean <30293.5) vs 9.6m in high NE expression (p=0.06). MMPs, uPA, and Arginase were not associated with survival. Conclusions: Higher CTSB expression is associated with statistically significant improvement in survival. CTSB is a lysosomal protease involved in processing antigens and overexpression could aid in immunologic cancer suppression. CTSB is also involved in the development of desmoplasia which is hypothesized to be a physical barrier to metastasis. CTSE and NE expression did not meet statistically significant association with survival, likely due to sample size. Hence, we identify CTSB as a potential prognostic biomarker in pancreatic cancer. However, these findings need to be validated in a larger study. [Table: see text]

Circumstellar environment of the M-type AGB star R Doradus

Context. Our current insights into the circumstellar chemistry of asymptotic giant branch (AGB) stars are largely based on studies of carbon-rich stars and stars with high mass-loss rates. Aims. In order to expand the current molecular inventory of evolved stars we present a spectral scan of the nearby, oxygen-rich star R Dor, a star with a low mass-loss rate (~2 × 10−7 M⊙ yr−1). Methods. We carried out a spectral scan in the frequency ranges 159.0–321.5 GHz and 338.5–368.5 GHz (wavelength range 0.8–1.9 mm) using the SEPIA/Band-5 and SHeFI instruments on the APEX telescope and we compare it to previous surveys, including one of the oxygen-rich AGB star IK Tau, which has a high mass-loss rate (~5 ×10−6 M⊙ yr−1). Results. The spectrum of R Dor is dominated by emission lines of SO2 and the different isotopologues of SiO. We also detect CO, H2O, HCN, CN, PO, PN, SO, and tentatively TiO2, AlO, and NaCl. Sixteen out of approximately 320 spectral features remain unidentified. Among these is a strong but previously unknown maser at 354.2 GHz, which we suggest could pertain to H2SiO, silanone. With the exception of one, none of these unidentified lines are found in a similarly sensitive survey of IK Tau performed with the IRAM 30 m telescope. We present radiative transfer models for five isotopologues of SiO (28SiO, 29SiO, 30SiO, Si17O, Si18O), providing constraints on their fractional abundance and radial extent. We derive isotopic ratios for C, O, Si, and S and estimate that, based on our results for 17O/18O, R Dor likely had an initial mass in the range 1.3–1.6 M⊙, in agreement with earlier findings based on models of H2O line emission. From the presence of spectral features recurring in many of the measured thermal and maser emission lines we tentatively identify up to five kinematical components in the outflow of R Dor, indicating deviations from a smooth, spherical wind.

ALMA detection of a tentative nearly edge-on rotating disk around the nearby AGB star R Doradus

A spectral scan of the circumstellar environment of the asymptotic giant branch (AGB) star R Doradus was taken with ALMA in cycle 2 at frequencies between 335 and 362 GHz and with a spatial resolution of ~150 milliarcseconds. Many molecular lines show a spatial offset between the blue and red shifted emission in the innermost regions of the wind. The position-velocity diagrams of this feature, in combination with previous SPHERE data and theoretical work point towards the presence of a compact differentially rotating disk, orientated nearly edge-on. We model the 28SiO (v = 1, J = 8 → 7) emission with a disk model. We estimate the disk mass and angular momentum to be 3 × 10−6 M⊙ and 5 × 1040 m2 kg s−1. The latter presents an “angular momentum problem” that may be solved by assuming that the disk is the result of wind-companion interactions with a companion of at least 2.5 earth masses, located at 6 AU, the tentatively determined location of the disk’s inner rim. An isolated clump of emission is detected to the south-east with a velocity that is high compared to the previously determined terminal velocity of the wind. Its position and mean velocity suggest that it may be associated with a companion planet, located at the disk’s inner rim.

Performance of the FMI cosine error correction method for the Brewer spectral UV measurements

The performance of the cosine error correction method used at the Finnish Meteorological Institute (FMI) for correcting spectral UV measurements of the Brewer spectroradiometer (Brewer) was studied. An instrument specific cosine error correction has to be applied due to the non ideal angular response of the Brewer. The correction depends on the actual sky radiation distribution, which can change even during one spectral scan due to rapid changes in cloudiness. The method has been developed to take into account such changes and derive a correction coefficient for each measured wavelength. Measurements of five Brewers were corrected using the method and the results were compared to a travel reference spectroradiometer (QASUME). Measurements were performed during the RBCC-E (Regional Brewer Calibration Center – Europe) X Campaign held at El Arenosillo, Huelva (37° N, 7° W), Spain, in 2015. In addition, results of site audits of FMI’s Brewers in Sodankylä (67° N, 23° W) and Jokioinen (61° N, 24° W) during 2002–2014 were studied. The results showed that the spectral cosine error correction varied between 4 to 14 %, and the differences between the QASUME and the Brewers diminished by up to 10 %. The study showed that the method, originally developed for measurements made at high latitudes, can be used at midlatitudes as well. It also showed that the method is applicable to other Brewers as far as required input parameters, i.e., total ozone, information from aerosols, albedo, instrument specific angular response and slit function, are known.

Ultraluminous Extragalactic Chemistry

At a distance of 77 Mpc, the Ultralumious galaxy Arp 220 is the closest extragalactic equivalent to Galactic hot cores. The low resolution SMA survey showed a highly excited confusion limited spectrum. The new ALMA snapshot spectral scan opens the possibility of chemically resolve the two nuclei at unprecedented sensitivity. When completed, it will be the widest survey ever done towards an extragalactic object. The model of Band 6 and 7 data already shows the chemical similarities between the interacting nuclei which may provide clues on the similar heating sources. Vibrationally excited transitions may be tracing the deeply embedded dust obscured active nuclei and/or hot compact star burst. This vibrational emission is the brightest ever measured in an extragalactic object, and even so compared with Galactic hot cores. In fact, the eastern one is the brightest in such vibrational emission. Water mega-maser emission also points towards a very compact sources likely related to star forming clumps within both Arp 220 nuclei.

Ultraviolet Absorption Spectral Scan and Fluorescence Emission Spectral Scan Analysis: Potential Tests with Diagnostic Utility in Porphyria

ABSTRACT Introduction Symptoms of porphyria usually overlap with other clinical conditions, thereby leading to misdiagnosis and inappropriate treatment, especially when patient presents with uncommon features. An accurate diagnosis of porphyria can be made only when enzyme defects can be detected, which is costly and not easily available. Classically, Ehrlich's test used to screen porphyria has certain disadvantages too. Hence, we planned this study. Aim To develop comparatively simpler diagnostic tests feasible at tertiary care centers to work up porphyria cases. Materials and methods A suspected case of porphyria was screened using Ehrlich's test. Thereafter, patient's urine and serum samples were analyzed by ultraviolet (UV) absorption spectral scan and fluorescence emission spectral scan using multimode microplate reader and compared against normal controls to validate the results. Results The UV absorption spectral scan revealed a small peak at 410 nm for patient's urine sample, which intensified on acidification. The UV absorption spectral scan for patient's serum also showed absorbance peak at 405 nm vs normal serum. The fluorescence emission spectral scan of urine and serum of patient revealed a sharp emission peak at 626 nm, which was not present in respective samples of control. Fluorescence emission in patient's urine sample was 10.5 times more vs normal urine. Conclusion and clinical significance Novel methods like UV absorption spectral scan and fluorescence emission spectral scan using patient's urine and serum samples can be developed as diagnostic tests considering their practicality and affordability. Further, an algorithm formulated based on clinical features and basic lab tests can also identify the type of porphyria. How to cite this article Nimesh A, Agarwal V, Garg S, Mehndiratta M. Ultraviolet Absorption Spectral Scan and Fluorescence Emission Spectral Scan Analysis: Potential Tests with Diagnostic Utility in Porphyria. Indian J Med Biochem 2017;21(2):136-141.

FPGA-Based Micro Fiber-Optic Spectrometer Hardware Circuit System

Portability has become an inevitable trend of spectrometer. Faced with the trend, one micro fiber-optic spectrometer hardware circuit system, which regarded XC3S250E as master chip to control CCD scan, A/D conversion and USB data transmission, etc, was designed, and the corresponding circuits were designed. After consecutive spectral scan test, we can find that the designed spectrometer is able to complete the acquisition, conversion and transmission of spectrum. The system stability is very good and the scanning accuracy can reach 1nm.