Spectral Intensity Bioaerosol Sensor (SIBS): an instrument for spectrally resolved fluorescence detection of single particles in real time

Primary biological aerosol particles (PBAPs) in the atmosphere are highly relevant for the Earth system, climate, and public health. The analysis of PBAPs, however, remains challenging due to their high diversity and large spatiotemporal variability. For real-time PBAP analysis, light-induced fluorescence (LIF) instruments have been developed and widely used in laboratory and ambient studies. The interpretation of fluorescence data from these instruments, however, is often limited by a lack of spectroscopic information. This study introduces an instrument – the Spectral Intensity Bioaerosol Sensor (SIBS; Droplet Measurement Technologies (DMT), Longmont, CO, USA) – that resolves fluorescence spectra for single particles and thus promises to expand the scope of fluorescent PBAP quantification and classification. The SIBS shares key design components with the latest versions of the Wideband Integrated Bioaerosol Sensor (WIBS) and the findings presented here are also relevant for the widely deployed WIBS-4A and WIBS-NEO as well as other LIF instruments. The key features of the SIBS and the findings of this study can be summarized as follows. Particle sizing yields reproducible linear responses for particles in the range of 300&thinsp;nm to 20&thinsp;µm. The lower sizing limit is significantly smaller than for earlier commercial LIF instruments (e.g., WIBS-4A and the Ultraviolet Aerodynamic Particle Sizer; UV-APS), expanding the analytical scope into the accumulation-mode size range. Fluorescence spectra are recorded for two excitation wavelengths (λex=285 and 370&thinsp;nm) and a wide range of emission wavelengths (λmean=302–721&thinsp;nm) with a resolution of 16 detection channels, which is higher than for most other commercially available LIF bioaerosol sensors. Fluorescence spectra obtained for 16 reference compounds confirm that the SIBS provides sufficient spectral resolution to distinguish major modes of molecular fluorescence. For example, the SIBS resolves the spectral difference between bacteriochlorophyll and chlorophyll a and b. A spectral correction of the instrument-specific detector response is essential to use the full fluorescence emission range. Asymmetry factor (AF) data were assessed and were found to provide only limited analytical information. In test measurements with ambient air, the SIBS worked reliably and yielded characteristically different spectra for single particles in the coarse mode with an overall fluorescent particle fraction of ∼4&thinsp;% (3σ threshold), which is consistent with earlier studies in comparable environments.</ul

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Association between peri-operative angiotensin-converting enzyme inhibitors and angiotensin-2 receptor blockers and acute kidney injury in major elective non-cardiac surgery: a multicentre, prospective cohort study

The peri-operative use of angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers is thought to be associated with an increased risk of postoperative acute kidney injury. To reduce this risk, these agents are commonly withheld during the peri-operative period. This study aimed to investigate if withholding angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers peri-operatively reduces the risk of acute kidney injury following major non-cardiac surgery. Patients undergoing elective major surgery on the gastrointestinal tract and/or the liver were eligible for inclusion in this prospective study. The primary outcome was the development of acute kidney injury within seven days of operation. Adjusted multi-level models were used to account for centre-level effects and propensity score matching was used to reduce the effects of selection bias between treatment groups. A total of 949 patients were included from 160 centres across the UK and Republic of Ireland. From this population, 573 (60.4%) patients had their angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers withheld during the peri-operative period. One hundred and seventy-five (18.4%) patients developed acute kidney injury; there was no difference in the incidence of acute kidney injury between patients who had their angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers continued or withheld (107 (18.7%) vs. 68 (18.1%), respectively; p = 0.914). Following propensity matching, withholding angiotensin-converting enzyme inhibitors or angiotensin-2 receptor blockers did not demonstrate a protective effect against the development of postoperative acute kidney injury (OR (95%CI) 0.89 (0.58–1.34); p = 0.567)

Spectral Intensity Bioaerosol Sensor (SIBS): an instrument for spectrally resolved fluorescence detection of single particles in real time

Primary biological aerosol particles (PBAP) in the atmosphere are highly relevant for the Earth system, climate, and public health. The analysis of PBAP, however, remains challenging due to their high diversity and large spatiotemporal variability. For real-time PBAP analysis, light-induced fluorescence (LIF) instruments have been developed and widely used in laboratory and ambient studies. The interpretation of fluorescence data from these instruments, however, is often limited by a lack of spectroscopic information. This study introduces a new instrument – the Spectral Intensity Bioaerosol Sensor (SIBS) – that resolves fluorescence spectra for single particles and, thus, promises to expand the scope of fluorescent PBAP quantification and classification. The SIBS shares key design components with the latest versions of the Wideband Integrated Bioaerosol Sensor (WIBS) and the findings presented here are also relevant for the widely deployed WIBS-4A and WIBS-NEO as well as other LIF instruments. The key features of the SIBS and findings of this study can be summarized as follows: – Particle sizing yields reproducible linear responses for particles in the range of 300 nm to 20 µm. The lower sizing limit is significantly smaller than for earlier commercial LIF instruments (e.g., WIBS-4A and the Ultraviolet Aerodynamic Particle Sizer (UV-APS)), expanding the analytical scope into the accumulation mode size range. – Fluorescence spectra are recorded for two excitation wavelengths (λex = 285 and 370 nm) and a wide range of emission wavelengths (λmean = 302–721 nm) with a resolution of 16 detection channels, which is higher than for most other commercially available LIF bioaerosol sensors. – Fluorescence spectra obtained for 16 reference compounds confirm that the SIBS provides sufficient spectral resolution to distinguish major modes of molecular fluorescence. For example, the SIBS resolves the spectral difference between bacteriochlorophyll and chlorophyll a/b. – A spectral correction of the instrument-specific detector response is essential to use the full fluorescence emission range. – Asymmetry factor (AF) data were assessed and were found to provide only limited analytical information. – In test measurements with ambient air, the SIBS worked reliably and yielded characteristically different spectra for single particles in the coarse mode with an overall fluorescent particle fraction of ~ 4 % (3σ threshold), which is consistent with earlier studies in comparable environments

Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH

Direct measurement of the acidity (pH) of ambient aerosol particles/droplets has long been a challenge for atmospheric scientists. A novel and facile method was introduced recently by Craig et al. (2018), where the pH of size-resolved aerosol droplets was directly measured by two types of pH-indicator papers (pH ranges: 0–2.5 and 2.5–4.5) combined with RGB-based colorimetric analyses using a model of G − B (G minus B) versus pH2. Given the wide pH range of ambient aerosols, we optimize the RGB-based colorimetric analysis on pH papers with a wider detection range (pH ~ 0 to 6). Here, we propose a new model to establish the linear relationship between RGB values and pH: pHpredict = a × Rnormal + b × Gnormal + c × Bnormal. This model shows a wider applicability and higher accuracy than those in previous studies, and is thus recommended in future RGB-based colorimetric analyses on pH papers. Moreover, we identify one type of pH paper (Hydrion® Brilliant pH dip stiks, Lot Nr. 3110, Sigma-Aldrich) that is more applicable for ambient aerosols in terms of its wide pH detection range (0 to 6) and strong anti-interference capacity. The determined minimum sample mass (~ 180 μg) highlights its potential to predict aerosol pH with a high time resolution (e.g., ≤ 1 hour). We further show that the routinely adopted way of using pH color charts to predict aerosol pH may be biased by the mismatch between the standard colors on the color charts and the real colors of investigated samples. Thus, instead of using the producer-provided color chart, we suggest an in-situ calibration of pH papers with standard pH buffers

Size-Resolved Single-Particle Fluorescence Spectrometer for Real-Time Analysis of Bioaerosols: Laboratory Evaluation and Atmospheric Measurements

Characteristic particle size, fluorescence intensity, and fluorescence spectra are important features to detect and categorize bioaerosols. A prototype size-resolved single-particle fluorescence spectrometer (S2FS) was developed to simultaneously measure aerodynamic diameters and fluorescence spectra. Emission spectra are dispersed in 512 channels from 370 to 610 nm, where a major portion of biological fluorescence emission occurs. The S2FS consists of an aerodynamic particle sizer and a fluorescence spectrometer with a 355 nm laser excitation source and an intensified charge-coupled device as the detector. Highly fluorescent particles, such as Ambrosia artemisiifolia pollen and Olea europaea pollen, can be distinguished by the S2FS on a single-particle level. For weakly fluorescent particles, fluorescence spectra can only be obtained by averaging multiple particles (between 100 and 3000) of the same kind. Preliminary ambient measurements in Mainz (Germany, central Europe) show that an emission peak at ∼ 440 nm was frequently observed for fluorescent fine particles (0.5-1 μm). Fluorescent fine particles accounted for 2.8% on average based on the number fraction in the fine mode. Fluorescent coarse particles (>1 μm) accounted for 8.9% on average based on the number fraction, with strongest occurrence observed during a thunderstorm and in the morning

Spectral Intensity Bioaerosol Sensor (SIBS): A new Instrument for Spectrally Resolved Fluorescence Detection of Single Particles in Real-Time

Primary biological aerosol particles (PBAP) in the atmosphere are highly relevant for the Earth system, climate, and public health. The analysis of PBAP, however, remains challenging due to their high diversity and large spatiotemporal variability. For real-time PBAP analysis, light-induced fluorescence (LIF) instruments have been developed and widely used in laboratory and ambient studies. The interpretation of fluorescence data from these instruments, however, is often limited by a lack of spectroscopic information. This study introduces a new instrument – the Spectral Intensity Bioaerosol Sensor (SIBS) – that resolves fluorescence spectra for single particles and, thus, promises to expand the scope of fluorescent PBAP quantification and classification. The SIBS shares key design components with the latest versions of the Wideband Integrated Bioaerosol Sensor (WIBS) and the findings presented here are also relevant for the widely deployed WIBS-4A and WIBS-NEO as well as other LIF instruments. The key features of the SIBS and findings of this study can be summarized as follows: – Particle sizing yields reproducible linear responses for particles in the range of 300 nm to 20 µm. The lower sizing limit is significantly smaller than for earlier commercial LIF instruments (e.g., WIBS-4A and the Ultraviolet Aerodynamic Particle Sizer (UV-APS)), expanding the analytical scope into the accumulation mode size range. – Fluorescence spectra are recorded for two excitation wavelengths (λex = 285 and 370 nm) and a wide range of emission wavelengths (λmean = 302–721 nm) with a resolution of 16 detection channels, which is higher than for most other commercially available LIF bioaerosol sensors. – Fluorescence spectra obtained for 16 reference compounds confirm that the SIBS provides sufficient spectral resolution to distinguish major modes of molecular fluorescence. For example, the SIBS resolves the spectral difference between bacteriochlorophyll and chlorophyll a/b. – A spectral correction of the instrument-specific detector response is essential to use the full fluorescence emission range. – Asymmetry factor (AF) data were assessed and were found to provide only limited analytical information. – In test measurements with ambient air, the SIBS worked reliably and yielded characteristically different spectra for single particles in the coarse mode with an overall fluorescent particle fraction of ~ 4 % (3σ threshold), which is consistent with earlier studies in comparable environments

Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH

Direct measurement of the acidity (pH) of ambient aerosol particles/droplets has long been a challenge for atmospheric scientists. A novel and facile method was introduced recently by Craig et al. (2018), where the pH of size-resolved aerosol droplets was directly measured by two types of pH-indicator papers (pH ranges: 0–2.5 and 2.5–4.5) combined with RGB-based colorimetric analyses using a model of G−B (G minus B) vs. pH2. Given the wide pH range of ambient aerosols, we optimize the RGB-based colorimetric analysis on pH papers with a wider detection range (pH ∼ 0 to 6). Here, we propose a new model to establish the linear relationship between RGB values and pH: pHpredict = a⋅Rnormal+b⋅Gnormal+c⋅Bnormal. This model shows a wider applicability and higher accuracy than those in previous studies and is thus recommended in future RGB-based colorimetric analyses on pH papers. Moreover, we identify one type of pH paper (Hydrion® Brilliant pH dip stiks, lot no. 3110, Sigma-Aldrich) that is more applicable for ambient aerosols in terms of its wide pH detection range (0 to 6) and strong anti-interference capacity. Custom-made impactors are used to collect lab-generated aerosols on this type of pH paper. Preliminary tests show that, with a collected particle size range of ∼ 0.4–2.2 µm, the pH paper method can be used to predict aerosol pH with an overall uncertainty ≤ 0.5 units. Based on laboratory tests, a relatively short sampling time (∼ 1 to 4 h) is speculated for pH prediction of ambient aerosols. More importantly, our design of the impactors minimizes potential influences of changed environmental conditions during pH paper photographing processes on the predicted aerosol pH. We further show that the routinely adopted way of using pH color charts to predict aerosol pH may be biased by the mismatch between the standard colors on the color charts and the real colors of investigated samples. Thus, instead of using the producer-provided color charts, we suggest an in situ calibration of pH papers with standard pH buffers

Stress in student activities

В роботі встановлено, що основними причинами появу стресу у студентів є значні навчальні навантаження, які з’являються через велику кількість завдань з різних навчальних дисциплін. Все це призводить до поспіху і постійної нестачі часу. Найчастіше студенти відновлюють сили міцним сном і спілкуванням з друзями та близькими людьми.The paper found that the main cause of stress in students is a signi cant workload that appear because of the large number of tasks from different disciplines. All this leads to haste and constant lack of time. Most students soundly restore power and communicate with friends and loved ones