Ultrafast and precise distance measurement via real-time chirped pulse interferometry

Laser frequency combs, which are composed of a series of equally-spaced coherent frequency components, have triggered revolutionary progress for precision spectroscopy and optical metrology. Length/distance is of fundamental importance in both science and technology. In this work, we describe a ranging scheme based on chirped pulse interferometry. In contrast to the traditional spectral interferometry, the local oscillator is strongly chirped which is able to meet the measurement pulses at arbitrary distances, and therefore the dead zones can be removed. The distances can be precisely determined via two measurement steps based on time-of-flight method and synthetic wavelength interferometry, respectively. To overcome the speed limitation of the optical spectrum analyzer, the spectrograms are stretched and detected by a fast photodetector and oscilloscope, and consequently mapped into the time domain in real time. The experimental results indicate that the measurement uncertainty can be well within 2 \upmum, compared with the reference distance meter. The Allan deviation can reach 0.4 \upmum at averaging time of 4 ns, 25 nm at 1 \upmus, and can achieve 2 nm at 100 \upmus averaging time. We also measure a spinning disk with grooves of different depths to verify the measurement speed, and the results show that the grooves with about 150 m/s line speed can be clearly captured. Our method provides a unique combination of non-dead zones, ultrafast measurement speed, high precision and accuracy, large ambiguity range, and with only one single comb source. This system could offer a powerful solution for the field measurements in practical applications in future

Table_1_Gastrointestinal Talaromyces marneffei infection in a patient with AIDS: A case report and systematic review.docx

Talaromyces marneffei is a thermally dimorphic fungus that affects multiple organs and frequently invades immunocompromised individuals. However, only a few studies have reported the presence of intestinal infection associated with T. marneffei. Herein, we reported a case of intestinal T. marneffei infection in a man who complained of a 1-month history of intermittent fever, abdominal pain, and diarrhea. The result of the human immunodeficiency virus antibody test was positive. Periodic acid-Schiff and Gomorrah’s methylamine silver staining of the intestinal biopsy tissue revealed T. marneffei infection. Fortunately, the patient’s symptoms rapidly resolved with prompt antifungal treatment. In addition, we summarized and described the clinical characteristics, management, and outcomes of patients with intestinal T. marneffei infection. A total of 29 patients were identified, the majority of whom (65.52%) were comorbid with acquired immunodeficiency syndrome. The main clinical features included anemia, fever, abdominal pain, diarrhea, weight loss, and lymphadenopathy. The transverse and descending colon, ileocecum, and ascending colon were the most common sites of lesions. A considerable number of patients (31.03%) developed intestinal obstruction, intestinal perforation, and gastrointestinal bleeding. Of the 29 patients, six underwent surgery, 23 survived successfully with antifungal treatment, five died of T. marneffei infection, and one died of unknown causes. T. marneffei intestinal infection should be considered when immunodeficient patients in endemic areas present with non-specific symptoms, such as fever, abdominal pain, and diarrhea. Appropriate and timely endoscopy avoids delays in diagnosis. Early aggressive antifungal therapy improves the clinical outcomes of patients.</p