High performance continuous-wave laser cavity enhanced polarimetry using RF-induced linewidth broadening

We present precise optical rotation measurements of gaseous chiral samples using near-IR continuous-wave cavity-enhanced polarimetry. Optical rotation is determined by comparing cavity ring-down signals for two counter-propagating beams of orthogonal polarisation which are subject to polarisation rotation by the presence of both an optically active sample and a magneto-optic crystal. A broadband RF noise source applied to the laser drive current is used to tune the laser linewidth and optimise the polarimeter, and this noise-induced laser linewidth is quantified using self-heterodyne beat-note detection. We demonstrate the optical rotation measurement of gas phase samples of enantiomers of α-pinene and limonene with an optimum detection precision of 10 µdeg per cavity pass and an uncertainty in the specific rotation of ∼0.1 deg dm−1 (g/ml)−1 and determine the specific rotation parameters at 730 nm, for (+)- and (−)-α-pinene to be 32.10 ± 0.13 and −32.21 ± 0.11 deg dm−1 (g/ml)−1, respectively. Measurements of both a pure R-(+)-limonene sample and a non-racemic mixture of limonene of unknown enantiomeric excess are also presented, illustrating the utility of the technique

Sensitive detection of HO 2 radicals produced in an atmospheric pressure plasma using Faraday rotation cavity ring-down spectroscopy

Cavity ring-down spectroscopy (CRDS) is a well-established, highly sensitive absorption technique whose sensitivity and selectivity for trace radical sensing can be further enhanced by measuring the polarization rotation of the intracavity light by the paramagnetic samples in the presence of a magnetic field. In this paper, we highlight the use of this Faraday rotation cavity ring-down spectroscopy (FR-CRDS) for the detection of HO2 radicals. In particular, we use a cold atmospheric pressure plasma jet as a highly efficient source of HO2 radicals and show that FR-CRDS in the near-infrared spectral region (1506 nm) has the potential to be a useful tool for studying radical chemistry. By simultaneously measuring ring-down times of orthogonal linearly polarized light, measurements of Faraday effect-induced rotation angles (θ) and absorption coefficients (α) are retrieved from the same data set. The Faraday rotation measurement exhibits better long-term stability and enhanced sensitivity due to its differential nature, whereby highly correlated noise between the two channels and slow drifts cancel out. The bandwidth-normalized sensitivities are αmin=2.2×10-11 cm-1 Hz-1/2 and θmin=0.62 nrad Hz-1/2. The latter corresponds to a minimum detectable (circular) birefringence of Δnmin=5×10-16 Hz-1/2. Using the overlapping qQ3(N = 4-9) transitions of HO2, we estimate limits of detection of 3.1 × 108 cm-3 based on traditional (absorption) CRDS methods and 6.7 × 107 cm-3 using FR-CRDS detection, where each point of the spectrum was acquired during 2 s. In addition, Verdet constants for pertinent carrier (He, Ar) and bulk (N2, O2) gases were recorded in this spectral region for the first time. These show good agreement with recent measurements of air and values extrapolated from reported Verdet constants at shorter wavelengths, demonstrating the potential of FR-CRDS for measurements of very weak Faraday effects and providing a quantitative validation to the computed rotation angles

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Laser studies of chemical dynamics

In this thesis, resonance enhanced multiphoton ionisation (REMPI) in combination with time-of-flight mass spectrometry (TOF-MS) has been used to detect nascent photofragments resulting from the UV dissociation of a variety of small molecules. The translational anisotropy and angular momentum polarisation of these photofragments has been measured and used to elucidate the underlying photodissociation dynamics. Firstly, the photodissociation of NO2 at 320nm has been investigated and the vector correlations of the nascent NO photofragments have been measured in terms of a set of semi-classical bipolar moments. The measured angular momentum alignment is found to be consistent with an impulsive model for the dissociation, with μ and ν in the same molecular plane and both preferentially perpendicular to J, whilst angular momentum orientation measurements provide evidence for an additional torque due to the O-N-O bond opening during dissociation. These measurements were taken using a rotationally cooled, skimmed molecular beam and significant deviations were found between the bipolar moments measured using this source and previous measurements using a rotationally hotter source. The effect of parent molecular rotations on the measured bipolar moments has been quantified and successfully used to explain these deviations. The photodissociation of Cl2 has been studied in the wavelength region (320-350)nm. UV absorption in this wavelength region may result in two dissociation channels, (Cl+Cl) and (Cl+Cl*), and the angular momentum polarisation of both the Cl(2P3/2) and Cl*(2P1/2) photofragments has been measured. This angular momentum polarisation has been reported in terms of a polarisation parameter formalism which, together with the measured translational anisotropies, has been used to determine the different potential energy surfaces contributing to the dissociation process. Translational anisotropy measurements of the Cl(2P3/2) fragments have shown that, for the ground-state channel, dissociation results from a pure perpendicular transition to the C state, whilst alignment measurements show that non-adiabatic transitions to the A state are significant at large internuclear separations. The measured alignment parameters are found to be relatively constant for all dissociation wavelengths and are consistent with theoretical predictions. Translational anisotropy measurements of the Cl(2P_1/2) photofragments show that, for the excited-state channel, dissociation occurs following a mixed parallel and perpendicular excitation to the B and C states respectively and the interference between these two dissociation pathways has been shown to result in angular momentum orientation. The predissociation dynamics of the C 3Πg (ν=0) and (ν=1) Rydberg states of O2 has been extensively studied. The translational anisotropy and angular momentum alignment of the O(3P) and O(1D) photofragments resulting from this predissociation has been measured in terms of a polarisation parameter formalism, which has been extended for a two-photon dissociation process. Measurements have been taken at various fixed wavelengths within the two bands in order to investigate the differences in the predissociation dynamics of intermediate levels with different values of |Ω|(=0,1,2 in this case). The translational anisotropy is found to be dependent on the dissociation wavelength with the variations found to be consistent with rotational depolarisation due to the long lifetime of the excited C state. All photofragments have been found to be aligned, with the relationship between the measured O(3P) and O(1D) alignment being found to be consistent with a diabatic model of the dissociation. In addition, all photofragments are found to display coherent orientation resulting from interference between two possible two-photon absorption pathways. The measured orientation is affected by rotational depolarisation due to the long lifetime of the excited C state; once this effect is accounted for the orientation is found to be nearly constant over all dissociation wavelengths. The origin of the coherent orientation is attributed to two-photon absorption to different spin-orbit components of the C state.</p

Media 1: Directed assembly of optically bound matter

Originally published in Optics Express on 16 January 2012 (oe-20-2-1001

A first-in-class pan-lysyl oxidase inhibitor impairs stromal remodeling and enhances gemcitabine response and survival in pancreatic cancer

Published online: 28 August 2023. OnlinePublThe lysyl oxidase family represents a promising target in stromal targeting of solid tumors due to the importance of this family in crosslinking and stabilizing fibrillar collagens and its known role in tumor desmoplasia. Using small-molecule drug-design approaches, we generated and validated PXS-5505, a first-in-class highly selective and potent pan-lysyl oxidase inhibitor. We demonstrate in vitro and in vivo that pan-lysyl oxidase inhibition decreases chemotherapy-induced pancreatic tumor desmoplasia and stiffness, reduces cancer cell invasion and metastasis, improves tumor perfusion and enhances the efficacy of chemotherapy in the autochthonous genetically engineered KPC model, while also demonstrating antifibrotic effects in human patient-derived xenograft models of pancreatic cancer. PXS-5505 is orally bioavailable, safe and effective at inhibiting lysyl oxidase activity in tissues. Our findings present the rationale for progression of a pan-lysyl oxidase inhibitor aimed at eliciting a reduction in stromal matrix to potentiate chemotherapy in pancreatic ductal adenocarcinoma.Jessica L. Chitty ... Australian Pancreatic Cancer Genome Initiative (APGI) (Nan Q. Nguyen, Andrew R. Ruszkiewicz, Chris Worthley) ... et al