High fidelity probe and mitigation of mirror thermal fluctuations

Thermal noise arising from mechanical loss in high reflective dielectric coatings is a significant source of noise in precision optical measurements. In particular, Advanced LIGO, a large scale interferometer aiming to observed gravitational wave, is expected to be limited by coating thermal noise in the most sensitive region around 30–300 Hz. Various theoretical calculations for predicting coating Brownian noise have been proposed. However, due to the relatively limited knowledge of the coating material properties, an accurate approximation of the noise cannot be achieved. A testbed that can directly observed coating thermal noise close to Advanced LIGO band will serve as an indispensable tool to verify the calculations, study material properties of the coating, and estimate the detector’s performance.

This dissertation reports a setup that has sensitivity to observe wide band (10Hz to 1kHz) thermal noise from fused silica/tantala coating at room temperature from fixed-spacer Fabry–Perot cavities. Important fundamental noises and technical noises associated with the setup are discussed. The coating loss obtained from the measurement agrees with results reported in the literature. The setup serves as a testbed to study thermal noise in high reflective mirrors from different materials. One example is a heterostructure of Al_xGa_1−xAs (AlGaAs). An optimized design to minimize thermo–optic noise in the coating is proposed and discussed in this work.

Fluorescence pH probe based on microstructured polymer optical fiber

A kind of optical pH sensor was demonstrated that is based on a pH-sensitive fluorescence dye-doped (eosin) cellulose acetate (CA) thin-film modified microstructured polymer optical fiber (MPOF). It was obtained by directly inhaling an eosin-CA-acetic acid mixed solution into array holes in a MPOF and then removing the solvent (acetic acid). The sensing film showed different fluorescence intensities to different pH solutions in a pH range of 2.5-4.5. Furthermore, the pH response range could be tailored through doping a surfactant, hexadecyl trimethyl ammonium bromide (CTAB), in the sensing film. (c) 2007 Optical Society of America.

Fluorescence Hydrogen Peroxide Probe Based on a Microstructured Polymer Optical Fiber Modified with a Titanium Dioxide Film

A highly sensitive microstructured polymer optical fiber (MPOF) probe for hydrogen peroxide was made by forming a rhodamine 6G-doped titanium dioxide film on the side walls of array holes in an MPOF. It was found that hydrogen peroxide only has a response to the MPOF probe in a certain concentration of potassium iodide in sulfuric acid solution. The calibration graph of fluorescence intensity versus hydrogen peroxide concentration is linear in the range of 1.6 x 10(-7) mol/L to 9.6 x 10(-5) mol/L. The method, with high sensitivity and a wide linear range, has been applied to the determination of trace amounts of hydrogen peroxide in a few real samples, such as rain water and contact lens disinfectant, with satisfactory results.

Neutron-proton bremsstrahlung from intermediate energy heavy-ion reactions as a probe of the nuclear symmetry energy?

Hard photons from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions are examined as a potential probe of the nuclear symmetry energy within a transport model. Effects of the symmetry energy on the yields and spectra of hard photons are found to be generally smaller than those due to the currently existing uncertainties of both the in-medium nucleon-nucleon cross sections and the photon production probability in the elementary process pn -> pn gamma. Very interestingly, nevertheless, the ratio of hard photon spectra R-1/2(gamma) from two reactions using isotopes of the same element is not only approximately independent of these uncertainties but also quite sensitive to the symmetry energy. For the head-on reactions of Sn-132 + Sn-124 and Sn-112 + Sn-112 at E-beam/A = 50 MeV, for example, the R-1/2(gamma) displays a rise up to 15% when the symmetry energy is reduced by about 20% at rho = 1.3 rho(0) which is the maximum density reached in these reactions. (C) 2008 Elsevier B.V. All rights reserved.

Possible probe on the momentum dependent interaction in the equation of state of nuclear matter

The effects of momentum dependent interaction on the kinetic energy spectrum of the neutron-proton ratio r(b)(E-k) in the equation of state of nuclear matter was investigated. We found that the kinetic energy spectrum of the neutron-proton ratio r(b)(E-k) depends sensitively on the momentum dependent interaction and weakly on the in-medium nucleon-nucleon cross section and symmetry potential so that the r(b) (E-k) is a sensitive physical probe for extracting the information of momentum dependent interaction in the heavy ion collisions. At the same time, the comparing investigate between r(b)(E-k) for the neutron-rich collision system and the same mass stable collision system gives a important judgment for extracting the information of momentum dependent interaction in the heavy ion collisions.

A sensitive impedimetric thrombin aptasensor based on polyamidoamine dendrimer

A label-free and highly sensitive impedimetric aptasensor based on a polyamidoamine dendrimer modified gold electrode was developed for the determination of thrombin. Amino-terminated polyamidoamine dendrimer was firstly covalently attached to the cysteine functionalized gold electrode through glutaraldehyde coupling. Subsequently, the dendrimer was activated with glutaraldehyde, and amino-modified thrombin aptamer probe was immobilized onto the activated dendrimer monolayer film. The layer-by-layer assembly process was traced by surface plasmon resonance and electrochemical impedance spectroscopy.

DNA based gold nanoparticles colorimetric sensors for sensitive and selective detection of Ag(I) ions

In this work, we reported both unlabeled and labeled sensing strategies for Ag(I) ions detection by using the DNA based gold nanoparticles (AuNPs) colorimetric method. In the unlabeled strategy, C-base riched single strand DNA (C-ssDNA) enwinded onto AuNPs to form AuNPs/C-ssDNA complex. In the labeled method, sulfhydryl group modified C-ssDNA (HS-C-ssDNA) was covalently labeled on AuNPs to produce AuNPs-S-C-ssDNA complex. In both strategies, C-ss DNA or HS-C-ssDNA could enhance the AuNPs stability against the salt-induced aggregation. However, the presence of Ag(I) ions in the obtained AuNPs/C-ssDNA or AuNPs-S-C-ssDNA complex would decrease such stability to display purple even blue colors due to the formation of Ag(I) ions mediated C-Ag(I)-C base pairs. Through this phenomenon, Ag(I) ions could be detected qualitatively and quantitatively using both unlabeled and labeled sensing strategies.

Methylene blue as an indicator for sensitive electrochemical detection of adenosine based on aptamer switch

In this paper, a simple, label-free and regenerative method was proposed to study the interaction between aptamer and small molecule by using methylene blue (MB+) as an electrochemical indicator. A thiolated capture probe containing twelve bases was firstly self-assembled on gold electrode by gold-sulfur affinity. Aptamer probe containing thirty two bases, which was designed to hybridize with capture DNA sequence and specifically recognize adenosine, was then immobilized on the electrode surface by hybridization reaction. MB+ was abundantly adsorbed on the aptamer probe by the specific interaction between MB+ and guanine base in aptamer probe. MB+-anchored aptamer probe can be forced to dissociate from the sensing interface after adenosine triggered structure switching of the aptamer. The peak current of MB+ linearly decreased with the concentration of adenosine over a range of 2 x 10 (8)- x 10 (6) M with a detection limit of 1 x 10 (8) M. In addition, we examined the selectivity of this electrochemical biosensor for cytidine, uridine and guanosine that belonged to the nucleosides family and possessed 1 similar structure with adenosine.

Electrochemical probe of hydroxylation of 4-nitrophenol by cytochrome c with hydrogen peroxide

The reaction of hydrogen peroxide with cytochrome c makes them coupled to lead to the hydroxylation of 4-nitrophenol. In situ electrochemical probe was used to detect the hydroxylation of 4-nitrophenol, which can avoid the tedious extraction procedure, the loss of the active species and the interference of some colored substances in the detection of 4-nitrocatechol by spectroscopic method. The hydroxyl radical scavengers mannitol and sodium benzoate did not eliminate hydroxylation, but the inhibitory effect of uric acid on the hydroxylation lead to the formation of the ferryl species of the protein during the reaction. These studies suggest that the electrochemical probe might efficiently detect the trace 4-nitrocatechol from the onset of the hydroxylation reaction and thus provides a more sensitive tool.

A new europium chelate-based phosphorescence probe specific for singlet oxygen

The first Eu3+ chelate-based phosphorescence probe specific for singlet oxygen has been designed, synthesized and characterized. The probe is highly sensitive, selective and water soluble for time-resolved luminescence detection of singlet oxygen with a detection limit of 2.8 nM.

Rapid differentiation between fluconazole-sensitive and -resistant species of Candida directly from positive blood-culture bottles by real-time PCR

In view of both the delay in obtaining identification by conventional methods following blood-culture positivity in patients with candidaemia and the close relationship between species and fluconazole (FLC) susceptibility, early speciation of positive blood cultures has the potential to influence therapeutic decisions. The aim was to develop a rapid test to differentiate FLC-resistant from FLC-sensitive Candida species. Three TaqMan-based real-time PCR assays were developed to identify up to six Candida species directly from BacT/Alert blood-culture bottles that showed yeast cells on Gram staining at the time of initial positivity. Target sequences in the rRNA gene complex were amplified, using a consensus two-step PCR protocol, to identify Candida albicans, Candida parapsilosis, Candida tropicalis, Candida dubliniensis, Candida glabrata and Candida krusei; these are the most commonly encountered Candida species in blood cultures. The first four of these (the characteristically FLC-sensitive group) were identified in a single reaction tube using one fluorescent TaqMan probe targeting 1 8S rRNA sequences conserved in the four species. The FLC-resistant species C. krusei and C. glabrata were detected in two further reactions, each with species-specific probes. This method was validated with clinical specimens (blood cultures) positive for yeast (n=33 sets) and the results were 100% concordant with those of phenotypic identification carried out concomitantly. The reported assay significantly reduces the time required to identify the presence of C. glabrata and C. krusei in comparison with a conventional phenotypic method, from ~72 to

Novel hydrolysis-probe based qPCR assay to detect saxitoxin transcripts of dinoflagellates in environmental samples

Paralytic Shellfish Poisoning (PSP) is a serious human illness caused by ingestion of seafood enriched with paralytic shellfish toxins (PSTs). PSTs are neurotoxic compounds produced by marine dinoflagellates, specifically by Alexandrium spp., Gymnodinium catenatum and Pyrodinium bahamense. Every year, massive monitoring of PSTs and their producers is undertaken worldwide to avoid PSP incidences. Here we developed a sensitive, hydrolysis probe-based quantitative PCR (qPCR) assay to detect a gene essential for PST synthesis across different dinoflagellate species and genera and tested it on cDNA generated from environmental samples spiked with Alexandrium minutum or Alexandrium fundyense cells. The assay was then applied to two environmental sample series from Norway and Spain and the results were complemented with cell counts, LSU-based microarray data and toxin measurements (enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) biosensor method). The overall agreement between the results of the qPCR assay and the complementary data was good. The assay reliably detected sxtA transcripts from Alexandrium spp. and G. catenatum, even though Alexandrium spp. cell concentrations were mostly so low that they could not be quantified microscopically. Agreement between the novel assay and toxin measurements or cell counts was generally good; the few inconsistencies observed were most likely due to disparate residence times of sxtA transcripts and PSTs in seawater, or, in the case of cell counts, to dissimilar sxtA4 transcript numbers per cell in different dinoflagellate strains or species. © 2013 Elsevier B.V.

Influence of test methodology and probe geometry on nanoscale fatigue mechanisms of diamond-like carbon thin film

The aim of this paper is to investigate the mechanism of nanoscale fatigue using nano-impact and multiple-loading cycle nanoindentation tests, and compare it to previously reported findings of nanoscale fatigue using integrated stiffness and depth sensing approach. Two different film loading mechanism, loading history and indenter shapes are compared to comprehend the influence of test methodology on the nanoscale fatigue failure mechanisms of DLC film. An amorphous 100 nm thick DLC film was deposited on a 500 μm silicon substrate using sputtering of graphite target in pure argon atmosphere. Nano-impact and multiple-load cycle indentations were performed in the load range of 100 μN to 1000 μN and 0.1 mN to 100 mN, respectively. Both test types were conducted using conical and Berkovich indenters. Results indicate that for the case of conical indenter, the combination of nano-impact and multiple-loading cycle nanoindentation tests provide information on the life and failure mechanism of DLC film, which is comparable to the previously reported findings using the integrated stiffness and depth sensing approach. However, the comparison of results is sensitive to the applied load, loading mechanism, test-type and probe geometry. The loading mechanism and load history is therefore critical which also leads to two different definitions of film failure. The choice of exact test methodology, load and probe geometry should therefore be dictated by the in-service tribological conditions, and where necessary both test methodologies can be used to provide better insights of failure mechanism. Molecular dynamics (MD) simulations of the elastic response of nanoindentation is reported, which indicates that the elastic modulus of the film measured using MD simulation was higher than that experimentally measured. This difference is attributed to the factors related to the presence of material defects, crystal structure, residual stress, indenter geometry and loading/unloading rate differences between the MD and experimental results.

Active site labeling of cysteine cathepsins by a straightforward diazomethylketone probe derived from the N-terminus of human cystatin C

We designed a straightforward biotinylated probe using the N-terminal substrate-like region of the inhibitory site of human cystatin C as a scaffold, linked to the thiol-specific reagent diazomethylketone group as a covalent warhead (i.e. Biot-(PEG)2-Ahx-LeuValGly-DMK). The irreversible activity-based probe bound readily to cysteine cathepsins B, L, S and K. Moreover affinity labeling is sensitive since active cathepsins were detected in the nM range using an ExtrAvidin®-peroxidase conjugate for disclosure. Biot-(PEG)2-Ahx-LeuValGly-DMK allowed a slightly more pronounced labeling for cathepsin S with a compelling second-order rate constant for association (kass = 2,320,000 M−1 s−1). Labeling of the active site is dose-dependent as observed using 6-cyclohexylamine-4-piperazinyl-1,3,5-triazine-2-carbonitrile, as competitive inhibitor of cathepsins. Finally we showed that Biot-(PEG)2-Ahx-LeuValGly-DMK may be a simple and convenient tool to label secreted and intracellular active cathepsins using a myelomonocytic cell line (THP-1 cells) as model.

Highly Sensitive Fluorescent Method for the Detection of Cholesterol Aldehydes Formed by Ozone and Singlet Molecular Oxygen

Cholesterol oxidation gives rise to a mixture of oxidized products. Different types of products are generated according to the reactive species being involved. Recently, attention has been focused on two cholesterol aldehydes, 3 beta-hydroxy-5 beta-hydroxy-B-norcholestane-6 beta-carboxyaldehyde (1a) and 3 beta-hydroxy-5-oxo-5,6-secocholestan-6-al (1b). These aldehydes can be generated by ozone-, as well as by singlet molecular oxygen-mediated cholesterol oxidation. It has been suggested that 1b is preferentially formed by ozone and la is preferentially formed by singlet molecular oxygen. In this study we describe the use of 1-pyrenebutyric hydrazine (PBH) as a fluorescent probe for the detection of cholesterol aldehydes. The formation of the fluorescent adduct between la with PBH was confirmed by HPLC-MS/MS. The fluorescence spectra of PBH did not change upon binding to the aldehyde. Moreover, the derivatization was also effective in the absence of an acidified medium, which is critical to avoid the formation of cholesterol aldehydes through Hock cleavage of 5 alpha-hydroperoxycholesterol. In conclusion, PBH can be used as an efficient fluorescent probe for the detection/quantification of cholesterol aldehydes in biological samples. Its analysis by HPLC coupled to a fluorescent detector provides a sensitive and specific way to quantify cholesterol aldehydes in the low femtomol range.