Procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry.

A procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry that does not require access to laser frequency measuring instrumentation is presented. It requires a previously well-characterized system regarding mirror phase shifts, Gouy phase, and mode number, and is based on the fact that the assessed refractivity should not change when mode jumps take place. It is demonstrated that the procedure is capable of assessing mode frequencies with an uncertainty of 30 MHz, which, when assessing pressure of nitrogen, corresponds to an uncertainty of 0.3 mPa.

Demonstration of a Transportable Fabry-Pérot Refractometer by a Ring-Type Comparison of Dead-Weight Pressure Balances at Four European National Metrology Institutes.

Fabry-Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10-90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry.

In situ determination of the penetration depth of mirrors in Fabry-Perot refractometers and its influence on assessment of refractivity and pressure.

A procedure is presented for in situ determination of the frequency penetration depth of coated mirrors in Fabry-Perot (FP) based refractometers and its influence on the assessment of refractivity and pressure. It is based on assessments of the absolute frequency of the laser and the free spectral range of the cavity. The procedure is demonstrated on an Invar-based FP cavity system with high-reflection mirrors working at 1.55 µm. The influence was assessed with such a low uncertainty that it does not significantly contribute to the uncertainties (k = 2) in the assessment of refractivity (<8 × 10-13) or pressure of nitrogen (<0.3 mPa).

LiMAx Test Improves Diagnosis of Chemotherapy-Associated Liver Injury Before Resection of Colorectal Liver Metastases.

BACKGROUND: Chemotherapy of colorectal liver metastases (CLMs) prior to liver resection implies the risk of chemotherapy-associated liver injury, leading to increased postoperative morbidity and mortality OBJECTIVE: The aim of this study was to evaluate the LiMAx (liver maximum capacity) test for diagnosis of chemotherapy-associated liver injury. METHODS: This was a retrospective analysis of patients with CLMs, prior to liver resection. We performed preoperative assessment of liver function using biochemical parameters and the LiMAx test. The individual history of chemotherapy within 12 months, including regimen, number of cycles, and therapy-free interval were collected, and histopathological evaluation of tumor-free liver tissue was performed in resected patients. RESULTS: A total of 204 patients were included, of whom 127 (62%) had received previous chemotherapy. The LiMAx test was worse after chemotherapy (340 ± 95 vs. 391 ± 82 µg/kg/h; p < 0.001). Impaired LiMAx results (<315 µg/kg/h) were determined in 49% of patients after chemotherapy, and no effects of chemotherapy, liver steatosis or fibrosis on biochemical parameters were observed. LiMAx impairment was dependent on the number of oxaliplatin cycles, the therapy-free interval, and obesity in multivariate analysis. In addition, the LiMAx test was worse in patients with relevant steatosis, fibrosis and steatohepatitis. Patients with an impaired LiMAx showed sufficient regeneration during chemotherapy cessation when surgery was postponed (272 ± 57 - 348 ± 72 µg/kg/h; p = 0.003). CONCLUSION: The LiMAx test enables non-invasive preoperative diagnosis of chemotherapy-associated liver injury. Preoperative performance of the LiMAx test can augment surgical strategy and timing of surgery after previous chemotherapy, thus avoiding increased postoperative morbidity.

Kinetic validation of the LiMAx test during 10 000 intravenous 13C-methacetin breath tests.

The maximal liver function capacity (LiMAx) test, a novel 13C-methacetin breath test, has proven clinical validity in determining hepatic metabolic capacity. In contrast to prior 13C-methacetin breath test protocols, the LiMAx test is performed by intravenous body-weight-adjusted substrate administration. Furthermore, the DOB kinetics (delta over baseline of the time-dependent exhaled 13CO2/12CO2 ratio) are measured online at the bedside with a high time resolution in order to determine the maximum DOB. The aim of this study was to analyze the recorded DOB kinetics in a large population for further refinement of the test protocol. Two new methods of kinetic analysis are proposed in this article: the time dependency of the DOB kinetics and the time interval until half of the DOB maximum. A total of 10 100 LiMAx tests on 8483 patients performed during routine clinics at eight centers were available. The kinetic analysis revealed a specific pattern of DOB kinetics depending upon LiMAx result. In addition, potential co-factors for DOB kinetics, such as weight, height, gender and age, were analyzed, yielding a potential influence of gender and smoking behavior. Both the specific patterns and the proposed kinetic analysis have the potential to further improve the sensitivity and specificity of the test and its clinical applicability by shortening its duration.