Doubly resonant photoacoustic spectroscopy: ultra-high sensitivity meets ultra-wide dynamic range

Photoacoustic spectroscopy (PAS) based gas sensors with high sensitivity, wide dynamic range, low cost, and small footprint are desirable across a broad range of applications in energy, environment, safety, and public health. However, most works have focused on either acoustic resonator to enhance acoustic wave or optical resonator to enhance optical wave. Herein, we develop a gas sensor based on doubly resonant PAS in which the acoustic and optical waves are simultaneously enhanced using combined optical and acoustic resonators in a centimeter-long configuration. Not only the lower detection limit is enhanced by the double standing waves, but also the upper detection limit is expanded due to the short resonators. As an example, we developed a sensor by detecting acetylene (C2H2), achieving a noise equivalent absorption of 5.7*10-13 cm-1 and a dynamic range of eight orders. Compared to the state-of-the-art PAS gas sensors, the developed sensor increases the sensitivity by two orders of magnitude and extends the dynamic range by three orders of magnitude. Besides, a laser-cavity-molecule locking strategy is proposed to provide additional flexibility of fast gas detection

Compact and Versatile QEPAS-Based Sensor Box for Simultaneous Detection of Methane and Infrared Absorber Gas Molecules in Ambient Air

In this work we report on an innovative sensor box employing two acoustic detection modules connected in series for quartz-enhanced photoacoustic multi-gas detection. One detection module is coupled with an internal distributed-feedback quantum cascade laser (DFB-QCL) emitting at ∼7.719 µm for methane (CH4) sensing, while the second module has been designed to be coupled with an external laser source targeting the absorption features of a specific gas molecule Mx in the infrared spectral range. The sensor box can thus be employed for any application, depending on the CH4/Mx gas combination to be detected. The ∼7.719 µm DFB-QCL also allowed water vapor monitoring. To demonstrate the sensor versatility, we report on the QEPAS-box environmental monitoring application by simultaneously detecting in air methane, which is a greenhouse gas, nitric oxide (NO), an ozone depleting substance, and water vapor. Sensitivity levels of 4.30 mV ppm−1 and 17.51 mV ppm−1 and minimum detection limits of 48 ppb and 11 ppb for methane and nitric oxide detection were achieved, respectively. The sensor box operation was tested by analysing ambient air. Average concentrations of ∼1.73 ppm of CH4, ∼0.134 ppm of NO and 1.8% of H2O were measured

Single-tube on-beam quartz-enhanced photoacoustic spectroscopy.

Quartz-enhanced photoacoustic spectroscopy (QEPAS) with a single-tube acoustic microresonator (AmR) inserted between the prongs of a custom quartz tuning fork (QTF) was developed, investigated, and optimized experimentally. Due to the high acoustic coupling efficiency between the AmR and the QTF, the single-tube on-beam QEPAS spectrophone configuration improves the detection sensitivity by 2 orders of magnitude compared to a bare QTF. This approach significantly reduces the spectrophone size with respect to the traditional on-beam spectrophone configuration, thereby facilitating the laser beam alignment. A 1σ normalized noise equivalent absorption coefficient of 1.21×10(-8) cm(-1)·W/√Hz was obtained for dry CO2 detection at normal atmospheric pressure

Quartz enhanced photoacoustic H2S gas sensor based on a fiber-amplifier source and a custom tuning fork with large prong spacing

A quartz enhanced photoacoustic spectroscopy (QEPAS) sensor, employing an erbium-doped fiber amplified laser source and a custom quartz tuning fork (QTF) with its two prongs spaced ∼800 μm apart, is reported. The sensor employs an acoustic micro-resonator (AmR) which is assembled in an “on-beam” QEPAS configuration. Both length and vertical position of the AmR are optimized in terms of signal-to-noise ratio, significantly improving the QEPAS detection sensitivity by a factor of ∼40, compared to the case of a sensor using a bare custom QTF. The fiber-amplifier-enhanced QEPAS sensor is applied to H2S trace gas detection, reaching a sensitivity of ∼890 ppb at 1 s integration time, similar to those obtained with a power-enhanced QEPAS sensor equipped with a standard QTF, but with the advantages of easy optical alignment, simple installation, and long-term stability

Simultaneous dual-gas QEPAS detection based on a fundamental and overtone combined vibration of quartz tuning fork

A dual-gas quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor system based on a frequency division multiplexing technique of a quartz tuning fork (QTF) was developed and experimentally demonstrated. Two beams from two independently modulated lasers are focused at two different positions between the QTF prongs to excite both the QTF fundamental and 1st overtone flexural modes simultaneously. The 2f-wavelength modulation technique is employed by applying two sinusoidal dithers, whose frequencies are equal to a half of the QTF fundamental and 1st overtone frequencies, respectively, to the currents of two excitation lasers. The resonance frequency difference between two flexural modes ensures that the correlated photoacoustic signals generated by different target gases do not interfere with each other. The proposed QEPAS methodology realizes a continuous real-time dual-gas monitoring with a simple setup and small sensor size compared with previous multi-gas QEPAS sensors

Cancer screening uptake: association with individual characteristics, geographic distribution, and time trends in Italy

In Italy, organized screening programmes invite the vast majority of the population for cervical and breast cancer, and about one half of the population for colorectal cancer. Programme activity and quality are closely monitored. Nevertheless, there is a vast spontaneous activity, both public and private, for which information on service and coverage is missing. To estimate actual population coverage for the three types of screening the extent of spontaneous screening needs to be known

MANUAL WORKERS ARE MORE LIKELY TO ADOPT UNHEALTHY HABITS

Background. In Italy, organized screening programmes invite the vast majority of the population for cervical and breast cancer, and about one half of the population for colorectal cancer. Programme activity and quality are closely monitored. Nevertheless, there is a vast spontaneous activity, both public and private, for which information on service and coverage is missing. To estimate actual population coverage for the three types of screening the extent of spontaneous screening needs to be known. Methods. PASSI is a national telephone-interview surveillance system that continuously collects information about behavioural health risk factors and the diffusion of preventive health interventions. From 2010 to 2013, more than 151,000 18- to 69-year-olds were interviewed. During 2013, 136 out of 147 Italian local health authorities participated in the survey. Information about screening includes: test uptake (Pap smear, HPV, mammography, faecal occult blood test, colonoscopy), date of the last test, provider of the last test (whether paid or for free, proxy of the organized screening programme), reason for not participating in screening, and screening promotion/recommendation received. Individual information on socio-economic characteristics is available. Results. Seventy-seven percent of the 25-64 year-old women interviewed said they had undergone a Pap smear or HPV test in the three years before the interview, 40% within the screening programme, 37% spontaneously and paying. Seventy percent of the 50-69 year-old women interviewed reported having had a mammography in the two years before the interview, 51% within the screening programme, 19% spontaneously and paying. Thirty-eight percent of the 50-69 year olds interviewed reported having undergone colorectal screening in the two years before the interview, 31% within the screening programme, 7% spontaneously and paying. All three screening programmes showed a decreasing North-South trend in coverage. From 2010 to 2013, coverage increased for all types of screening; the trend was stronger in the South; the increase was mostly due to the tests performed within the organized programmes. People with low education, economic problems, and immigrants from high migration pressure countries had lower coverage levels. In regions with well-implemented organized screening programmes, test coverage was higher and differences for socio-economic factors were smaller than in regions with incomplete programme activation

Self-reported influenza vaccination uptake in people with chronic diseases: data from Progressi delle Aziende Sanitarie per la Salute in Italia (PASSI)

Background Influenza is an important public health problem, with potential severe consequences among people with chronic diseases. The aim of this study was to obtain reliable measures of seasonal influenza vaccine uptake in this population, otherwise not available in Italy. Methods Progressi delle Aziende Sanitarie per la Salute in Italia (PASSI) is a nationwide surveillance system of health-related behaviours and acceptance of preventive interventions (including influenza immunisation) offered by the Italian National Health Service. Data are collected with telephone interviews at local health unit level for supporting local activities. The survey sample is randomly selected from local health unit lists of adult residents. The trend of annual vaccine coverage since 2008 was estimated for people aged 18–64 years who reported having at least one chronic disease. To obtain a sufficient sample size in subgroups, we analysed the characteristics of vaccinated people in the 2010–13 cumulative dataset. Univariate, multivariate, and logistic regression analyses were undertaken. Findings In 2008–13, 13 659 individuals with at least one chronic disease were interviewed. Vaccination coverage fell significantly from 29·7% (95% CI 27·2–32·4) in 2007–08 to 19·9% (18·0–22·1) in 2012–13. During 2010–13, the overall proportion of vaccinated people with a chronic disease was 25·6% (24·5–26·7). Vaccine coverage of people with diabetes (34·3%, 31·7–36·9) or cardiovascular diseases (31·8%, 29·6–34·2) was greater than that of people affected by renal failure, respiratory diseases, tumours, or chronic liver diseases (26·5% [22·5–30·7], 24·9% [23·2–26·7], 22·2% [20·0–24·6], and 20·6% [17·5–24·6], respectively). Vaccination coverage increased with age (from 13·1% [11·0–15·5] in the 18–34 year age group to 33·4% [31·9–35·1] in people aged 50–64 years); it was higher among people with a low educational level than among those with a high educational level, higher in those having economic difficulties than in those with no economic difficulties, and higher among Italian citizens than among non-citizens. Interpretation In the past few years, prevalence of influenza vaccination in Italian adults with at least one chronic disease was well below the Ministry of Health's goal (75% minimum) and showed a downward trend. A major reason of this evolution is probably the changing public perception of the benefits and risks of vaccines. PASSI is a source of useful data not otherwise available for public health intervention. Funding Italian Ministry of Health

Self-reported influenza vaccination uptake in people with chronic diseases: data from Progressi delle Aziende Sanitarie per la Salute in Italia (PASSI)

Background Influenza is an important public health problem, with potential severe consequences among people with chronic diseases. The aim of this study was to obtain reliable measures of seasonal influenza vaccine uptake in this population, otherwise not available in Italy. Methods Progressi delle Aziende Sanitarie per la Salute in Italia (PASSI) is a nationwide surveillance system of health-related behaviours and acceptance of preventive interventions (including influenza immunisation) offered by the Italian National Health Service. Data are collected with telephone interviews at local health unit level for supporting local activities. The survey sample is randomly selected from local health unit lists of adult residents. The trend of annual vaccine coverage since 2008 was estimated for people aged 18\u201364 years who reported having at least one chronic disease. To obtain a sufficient sample size in subgroups, we analysed the characteristics of vaccinated people in the 2010\u201313 cumulative dataset. Univariate, multivariate, and logistic regression analyses were undertaken. Findings In 2008\u201313, 13\u2008659 individuals with at least one chronic disease were interviewed. Vaccination coverage fell significantly from 29\ub77% (95% CI 27\ub72\u201332\ub74) in 2007\u201308 to 19\ub79% (18\ub70\u201322\ub71) in 2012\u201313. During 2010\u201313, the overall proportion of vaccinated people with a chronic disease was 25\ub76% (24\ub75\u201326\ub77). Vaccine coverage of people with diabetes (34\ub73%, 31\ub77\u201336\ub79) or cardiovascular diseases (31\ub78%, 29\ub76\u201334\ub72) was greater than that of people affected by renal failure, respiratory diseases, tumours, or chronic liver diseases (26\ub75% [22\ub75\u201330\ub77], 24\ub79% [23\ub72\u201326\ub77], 22\ub72% [20\ub70\u201324\ub76], and 20\ub76% [17\ub75\u201324\ub76], respectively). Vaccination coverage increased with age (from 13\ub71% [11\ub70\u201315\ub75] in the 18\u201334 year age group to 33\ub74% [31\ub79\u201335\ub71] in people aged 50\u201364 years); it was higher among people with a low educational level than among those with a high educational level, higher in those having economic difficulties than in those with no economic difficulties, and higher among Italian citizens than among non-citizens. Interpretation In the past few years, prevalence of influenza vaccination in Italian adults with at least one chronic disease was well below the Ministry of Health's goal (75% minimum) and showed a downward trend. A major reason of this evolution is probably the changing public perception of the benefits and risks of vaccines. PASSI is a source of useful data not otherwise available for public health intervention. Funding Italian Ministry of Health