Ultra-broadband high-resolution microdroplet spectrometers for the near infrared.

By stabilizing the evaporation dynamics of a microliter fluorocarbon droplet, we demonstrate a fast-scan optofluidic Fourier transform (FT) spectrometer on the tip of an optical fiber operating in the 1000-2000 nm window with a resolution of 3.5 cm-1 (i.e., <1 nm at 1560 nm). Compared with other FT near-infrared (NIR) small-scale spectrometers reported in the literature, the fluorocarbon droplet spectrometer shows the largest wavelength span and span/resolution ratio, allowing spectral analysis of broadband or narrowband radiation to be easily performed. Our results open the way for the practical application of droplet spectrometers as advanced optofluidic NIR analyzers with small size and low cost that are capable of operating in harsh environments, even in the absence of electrical power sources.

Light pressure in droplet micro-resonators excited by free-space scattering.

A droplet optical resonator is a unique environment to investigate light-matter interaction and optomechanics in liquids. Here, we report on light pressure effects derived from whispering gallery modes excited in a liquid-polymer droplet micro-resonator by free-space laser scattering. From the nonlinear resonance spectrum observed in the visible, we provide evidence of photon pressure exerted at the liquid-air boundary and quantify it with a coherent physical model. Our findings pave the way to studies on micro-rheology and nonlinear optofluidics, where droplets serve as miniature liquid laboratories.

The impact of transanal local excision of early rectal cancer on completion rectal resection without neoadjuvant chemoradiotherapy: a systematic review.

BACKGROUND: The impact of transanal local excision (TAE) of early rectal cancer (ERC) on subsequent completion rectal resection (CRR) for unfavorable histology or margin involvement is unclear. The aim of this study was to provide a comprehensive review of the literature on the impact of TAE on CRR in patients without neoadjuvant chemoradiotherapy (CRT). METHODS: We performed a systematic review of the literature up to March 2020. Medline and Cochrane libraries were searched for studies reporting outcomes of CRR after TAE for ERC. We excluded patients who had neoadjuvant CRT and endoscopic local excision. Surgical, functional, pathological and oncological outcomes were assessed. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed. RESULTS: Sixteen studies involving 353 patients were included. Pathology following TAE was as follows T0 = 2 (0.5%); T1 = 154 (44.7%); T2 = 142 (41.2%); T3 = 43 (12.5%); Tx = 3 (0.8%); T not reported = 9. Fifty-three percent were > T1. Abdominoperineal resection (APR) was performed in 80 (23.2%) patients. Postoperative major morbidity and mortality occurred in 22 (11.4%) and 3 (1.1%), patients, respectively. An incomplete mesorectal fascia resulting in defects of the mesorectum was reported in 30 (24.6%) cases. Thirteen (12%) patients developed recurrence: 8 (3.1%) local, 19 (7.3%) distant, 4 (1.5%) local and distant. The 5-year cancer-specific survival was 92%. Only 1 study assessed anal function reporting no continence disorders in 11 patients. In the meta-analysis, CRR after TAE showed an increased APR rate (OR 5.25; 95% CI 1.27-21.8; p 0.020) and incomplete mesorectum rate (OR 3.48; 95% CI 1.32-9.19; p 0.010) compared to primary total mesorectal excision (TME). Two case matched studies reported no difference in recurrence rate and disease free survival respectively. CONCLUSIONS: The data are incomplete and of low quality. There was a tendency towards an increased risk of APR and poor specimen quality. It is necessary to improve the accuracy of preoperative staging of malignant rectal tumors in patients scheduled for TAE.

Practice parameters for the diagnosis and treatment of anal intraepithelial neoplasia (AIN) on behalf of the Italian Society of Colorectal Surgery (SICCR).

Squamous cell carcinoma (SCC) of the anus is a human papilloma virus (HPV) related malignancy that is preceded by anal intraepithelial neoplasia (AIN) making this cancer, at least theoretically, a preventable disease. In the past 10 years the diagnosis, management and nomenclature of AIN has dramatically changed. Increased life expectancy in human immunodeficiency virus (HIV) positive patients due to highly active antiretroviral therapy (HAART) has caused an increase in the incidence of SCC of the anus. While many experts recommend screening and treatment of anal high-grade squamous intraepithelial lesion (HSIL), there is no consensus on the optimal management these lesions. Therefore, there is a need to review the current evidence on diagnosis and treatment of AIN and formulate recommendations to guide management. Surgeons who are members of the Italian Society of Colorectal Surgery (SICCR) with a recognized interest in AIN were invited to contribute on various topics after a comprehensive literature search. Levels of evidence were classified using the Oxford Centre for Evidence-based Medicine of 2009 and the strength of recommendation was graded according to the United States (US) preventive services task force. These recommendations are among the few entirely dedicated only to the precursors of SCC of the anus and provide an evidence-based summary of the current knowledge about the management of AIN that will serve as a reference for clinicians involved in the treatment of patients at risk for anal cancer.

Opto-mechanical oscillator in a nanoliter droplet.

Droplets are very simple physical systems, whereby surface tension shapes liquids into ideal opto-mechanical devices. This has recently enabled low-viscosity liquid samples to serve as miniature acoustic resonators harnessing optical generation of bulk vibrations, capillaries, or surface waves. Uniquely, a simple room-temperature pendant droplet can be activated as a hypersound-laser emitter when illuminated by a free-space, low-power visible laser thanks to stimulated Brillouin scattering of optical and acoustic whispering-gallery modes. Here, we demonstrate continuous operation of a liquid polymer opto-mechanical resonator and characterize its quality factor and long-term frequency stability. Our results point to the feasibility of all-liquid micro-mechanical oscillators working in the 50-100 MHz range. The stimulated generation of high-quality surface waves on nanoliter droplets gives momentum to new optical schemes for characterization of material viscous-elastic properties, laboratory investigation of atmospheric phenomena, and mass sensing for direct analysis of biological fluids based on ultrasound-hypersound coherent generation and detection.

Stimulated Brillouin Cavity Optomechanics in Liquid Droplets.

Liquid droplets are ubiquitous in nature wherein surface tension shapes them into perfect spheres with atomic-scale smooth surfaces. Here, we use stable droplets that cohost equatorial acoustical and optical resonances phase matched to enable the exchange of energy and momentum between sound and light. Relying on free-space laser excitation of multiple whispering-gallery modes, we harness a triple-resonant forward Brillouin scattering to stimulate optomechanical surface waves. Nonlinear amplification of droplet vibrations in the 60-70 MHz range is realized with spectral narrowing beyond the limit of material loss, thereby activating the droplet as hypersound-laser emitter.

Restricted physical activity in pregnancy reduces maternal vascular resistance and improves fetal growth.

OBJECTIVES: To test the efficacy of maternal activity restriction for reducing peripheral vascular resistance in normotensive pregnant women with raised total vascular resistance (TVR) and to evaluate its effect on fetal growth. METHODS: This was a prospective case-control study of 30 women enrolled between 27 and 29 weeks' gestation. All patients met the following criteria: normal blood pressure before and during pregnancy, TVR between 1300 and 1400 dynes × s/cm5 at enrolment, normal fetal Doppler parameters at enrolment and abdominal circumference between the 10th and 25th centiles. Patients were assigned to activity restriction (activity-restriction group; n = 15) or no treatment (control group; n = 15) and were assessed after 4 weeks for TVR and fetal growth. RESULTS: TVR at enrolment and estimated fetal weight centile were similar in the activity-restriction group vs controls (1358 ± 26 vs 1353 ± 30 dynes × s/cm5 ; 18th ± 4 vs 19th ± 4 centile; P = NS). After 4 weeks, the activity-restriction group compared with controls showed significantly lower TVR (1165 ± 159 vs 1314 ± 190 dynes × s/cm5 ; P < 0.05), which was associated with higher estimated fetal weight centile (25th ± 5 vs 20th ± 5 centile; P < 0.05). TVR was lower and estimated fetal weight centile higher for the activity-restriction group after 4 weeks compared with at enrolment. CONCLUSIONS: In normotensive pregnant women with raised TVR, maternal activity restriction appears to be effective in reducing TVR and therefore enhancing fetal growth. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Maternal hemodynamics early in labor: a possible link with obstetric risk?

OBJECTIVE: To determine if hemodynamic assessment in 'low-risk' pregnant women at term with an appropriate-for-gestational age (AGA) fetus can improve the identification of patients who will suffer maternal or fetal/neonatal complications during labor. METHODS: This was a prospective observational study of 77 women with low-risk term pregnancy and AGA fetus, in the early stages of labor. Hemodynamic indices were obtained using the UltraSonic Cardiac Output Monitor (USCOM® ) system. Patients were followed until the end of labor to identify fetal/neonatal and maternal outcomes, and those which developed complications of labor were compared with those delivering without complications. RESULTS: Eleven (14.3%) patients had a complication during labor: in seven there was fetal distress and in four there were maternal complications (postpartum hemorrhage and/or uterine atony). Patients who developed complications during labor had lower cardiac output (5.6 ± 1.0 vs 6.7 ± 1.3 L/min, P = 0.01) and cardiac index (3.1 ± 0.6 vs 3.5 ± 0.7 L/min/m2 , P = 0.04), and higher total vascular resistance (1195.3 ± 205.3 vs 1017.8 ± 225.6 dynes × s/cm5 , P = 0.017) early in labor, compared with those who did not develop complications. Receiver-operating characteristics curve analysis to determine cut-offs showed cardiac output ≤ 5.8 L/min (sensitivity, 81.8%; specificity, 69.7%), cardiac index ≤ 2.9 L/min/m2 (sensitivity, 63.6%; specificity, 76.9%) and total vascular resistance > 1069 dynes × s/cm5 (sensitivity, 81.8%; specificity, 63.6%) to best predict maternal or fetal/neonatal complications. CONCLUSIONS: The study of maternal cardiovascular adaptation at the end of pregnancy could help to identify low-risk patients who may develop complications during labor. In particular, low cardiac output and high total vascular resistance are apparently associated with higher risk of fetal distress or maternal complications. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Screening for pre-eclampsia in the first trimester: role of maternal hemodynamics and bioimpedance in non-obese patients.

OBJECTIVE: To test if maternal hemodynamics and bioimpedance, assessed at the time of combined screening for PE, are able to identify in the first trimester of gestation normotensive non-obese patients at risk for pre-eclampsia (PE) and/or intrauterine growth restriction (IUGR). METHODS: One hundred and fifty healthy nulliparous non-obese women (body mass index < 30 kg/m2 ) in the first trimester of pregnancy underwent assessment by UltraSonic Cardiac Output Monitor (USCOM) to detect hemodynamic parameters, bioimpedance analysis to characterize body composition, and combined screening for PE (assessment of maternal history, biophysical and maternal biochemical markers). Patients were followed until term, noting the appearance of PE and/or IUGR. RESULTS: One hundred and thirty-eight patients had an uneventful pregnancy (controls), while 12 (8%) developed complications (cases). USCOM showed, in cases compared with controls, lower cardiac output (5.6 ± 0.3 vs 6.7 ± 1.1 L/min, P < 0.001), lower inotropy index (1.54 ± 0.38 vs 1.91 ± 0.32 W/m2 , P < 0.001) and higher total vascular resistance (1279.8 ± 166.4 vs 1061.4 ± 179.5 dynes × s/cm5 , P < 0.001). Bioimpedance analysis showed, in cases compared with controls, lower total body water (53.7 ± 3.3% vs 57.2 ± 5.6%, P = 0.037). Combined screening was positive for PE in 8% of the controls and in 50% of the cases (P < 0.001). After identification of cut-off values for USCOM and bioimpedance parameters, forward multivariate logistic regression analysis identified as independent predictors of complications in pregnancy the inotropy index (derived by USCOM), fat mass (derived from bioimpedance analysis) and combined screening. CONCLUSIONS: Combined screening for PE and assessment of bioimpedance and maternal hemodynamics can be used to identify early markers of impaired cardiovascular adaptation and body composition that may lead to complications in the third trimester of pregnancy. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Laser-frequency locking to a whispering-gallery-mode cavity by spatial interference of scattered light.

We present a simple and effective method for frequency locking a laser source to a free-space-coupled whispering-gallery-mode cavity. The scheme relies on the interference of spatial modes contained in the light scattered by the cavity, where low- and high-order modes are simultaneously excited. A dispersion-shaped signal proportional to the imaginary component of the resonant optical field is simply generated by spatial filtering of the scattered light. Locking of a diode laser to the equatorial modes of a liquid droplet resonator is demonstrated using this scheme, and its performance is compared to the Pound-Drever-Hall technique. This new approach makes laser-frequency locking straightforward and shows a number of advantages, including robustness, low cost, and no need for sophisticated optical and electronic components.

Fiber Bragg grating laser sensor with direct radio-frequency readout.

A fiber Bragg grating (FBG)-coupled ring laser sensor is demonstrated. In the proposed configuration the interrogating source, the sensing head and the readout instrument are integrated in a single fiber-optic device. An FBG inserted within a bidirectional fiber ring couples the two counterpropagating modes of the cavity, generating a splitting of the resonant wavelengths proportional to the FBG reflectivity. When the cavity gain is brought beyond threshold, the two peaks of the split resonances simultaneously lase, leading to a beat note in the emission spectrum whose frequency tracks any small shift of the FBG reflectivity spectrum. Such a beat note can be simply monitored by a frequency counter, without the need for an optical spectrometer, allowing to significantly reduce size and costs of the sensor setup. The sensing performance compares well to the state-of-the-art thermo-mechanical fiber sensors.

Mode-splitting cloning in birefringent fiber Bragg grating ring resonators.

In this Letter, we report the theoretical model and the experimental evidence of a mode-splitting cloning effect due to the resonant coupling between modes having different polarizations in weakly birefringent fiber Bragg grating (FBG) ring resonators. This modal coupling depends on the fiber birefringence and the FBG reflectivity. In the ideal case of the absence of birefringence, a single split-mode resonant structure can be observed in the resonator transmission spectrum due to the degeneracy removal of the two counter-propagating modes. In the presence of FBG birefringence, a secondary split doublet resulting in a clone of the initial one is generated. The described effect can be exploited for spectroscopic-sensing applications based on more complex split-mode dynamics.

Preterm delivery and elevated maternal total vascular resistance: signs of suboptimal cardiovascular adaptation to pregnancy?

OBJECTIVE: To evaluate the maternal hemodynamic profile in women with a diagnosis of threatened preterm delivery (TPD) in order to understand the possible pathophysiologic mechanism leading to an increased lifetime risk for future cardiovascular disease. METHODS: Patients with a diagnosis of TPD were enrolled and assessed using a non-invasive method (USCOM® ) for the determination of hemodynamic parameters. Vaginal and rectal swabs were taken, cervical length, blood inflammatory indices, fetal blood-vessel Doppler velocimetry were measured and gestational age at the time of delivery and neonatal outcomes were noted. RESULTS: A total of 68 patients were enrolled and included in the analysis. The population was divided into two groups according to total vascular resistance (TVR): Group A with a TVR of ≤ 1000 dynes × s/cm5 (n = 48) and Group B with a TVR of > 1000 dynes × s/cm5 (n = 20). C-reactive protein (CRP) was higher in Group B than in Group A, suggesting a systemic inflammation status. Group B delivered earlier (32 + 4 weeks vs 38 + 2 weeks; P < 0.01) and neonatal outcome was worse than in Group A. Significantly lower values of cardiac output, stroke volume, peak velocity of flow, velocity time integral, minute distance, stroke volume index, cardiac index, stroke work, cardiac power, inotropy index and potential-to-kinetic energy ratio were observed in Group B than in Group A. CONCLUSIONS: Women with a diagnosis of TPD showing TVR values of > 1000 dynes × s/cm5 and elevated levels of CRP are at high risk of preterm delivery. An impaired maternal cardiovascular adaptation during pregnancy in these patients might suggest a possible higher risk for subsequent future cardiovascular disease. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Body mass index and colorectal cancer prognosis: a systematic review and meta-analysis.

Colorectal cancer is one of the most common cancers worldwide. However, it is unclear what influence body mass index (BMI) has on colorectal cancer prognosis. We conducted a systematic review and meta-analysis of observational studies to examine the association of BMI with colorectal cancer outcomes. We searched MEDLINE and EMBASE databases from inception to February 2015 and references of identified articles. We selected observational studies that reported all-cause mortality, colorectal cancer-specific mortality, recurrence and disease-free survival according to BMI category. Random-effects meta-analyses were conducted to combine estimates. We included 18 observational studies. Obese patients had an increased risk of all-cause mortality [relative risk (RR) 1.14; 95 % confidence interval (CI) 1.07-1.21], cancer-specific mortality (RR 1.14; 95 % CI 1.05-1.24), recurrence (RR 1.07; 95 % CI 1.02-1.13) and worse disease-free survival (RR 1.07; 95 % CI 1.01-1.13). Underweight patients also had an increased risk of all-cause mortality (RR 1.43; 95 % CI 1.26-1.62), cancer-specific mortality (RR 1.50; 95 % CI 1.20-1.87), recurrence (RR 1.13; 95 % CI 1.05-1.21) and worse disease-free survival (RR 1.27; 95 % CI 1.13-1.43). Overweight patients had no increased risk for any of the outcomes studied. Both obese and underweight patients with colorectal cancer have an increased risk of all-cause mortality, cancer-specific mortality, disease recurrence and worse disease-free survival compared to normal weight patients.

Enhanced spectral response of π-phase shifted fiber Bragg gratings in closed-loop configuration.

The transmission spectrum of a ring resonator enclosing a π-phase shifted fiber Bragg grating (π-FBG) shows a spectral feature at the Bragg wavelength that is much sharper than resonance of the π-FBG alone, and that can be detected with a simple integrated cavity output technique. Hence, the resolution of any sensor based on the fitting of the π-FBG spectral profile can be largely improved by the proposed configuration at no additional fabrication costs and without altering the sensor robustness. A theoretical model shows that the resolution enhancement attainable in the proposed closed-loop geometry depends on the quality factor of the ring resonator. With a commercial grating in a medium-finesse ring, a spectral feature 12 times sharper than the π-FBG resonance is experimentally demonstrated. A larger enhancement is expected in a low-loss, polarization maintaining setup.

Psychological stress in patients with anal fistula.

AIM: Psychological stress is known to affect the immunologic system and the inflammatory response. The aim of this study was to assess the presence of psychological stress, anxiety, and depression in patients with anal fistula. METHODS: Consecutive patients with anal fistula, hemorrhoids, and normal volunteers were studied prospectively. Stressful life events were recorded and subjects were asked to complete the state-trait anxiety inventory (STAI), a depression scale, and three different reactive graphic tests (RGT). RESULTS: Seventy-eight fistula patients, 73 patients with grade III-IV hemorrhoids, and 37 normal volunteers were enrolled. Of the fistula patients, 65 (83 %) reported one or more stressful events in the year prior to diagnosis, compared to 16 (22 %) of the hemorrhoid patients (P = 0.001). There were no significant differences in the percentage of subjects with abnormal trait anxiety (i.e., proneness for anxiety) and depression scores between fistula patients, hemorrhoid patients, and controls. Fistula patients had significantly higher (i.e., better) scores compared to hemorrhoid patients in two of three RGT and significantly lower (i.e., worse) scores in all three RGT compared to healthy volunteers. Of 37 patients followed up for a median of 28 months (range 19-41 months) after surgery, 8 (21.6 %) had persistent or recurrent sepsis. There was no significant difference in depression, STAI, and RGT scores between patients with sepsis and patients whose fistula healed. CONCLUSION: Our results suggest that an altered emotional state plays an important role in the pathogenesis of anal fistula and underline the importance of psychological screening in patients with anorectal disorders.

High-sensitivity ring-down evanescent-wave sensing in fiber resonators.

We report on optical-fiber cavity ring-down spectroscopy (CRDS) in the liquid phase using a laser emitting at telecommunication wavelengths. A fiber-ring cavity, comprising a short evanescent-wave coupler for radiation-matter interaction, is used as a sensor while its resonance modes are frequency locked to the laser. Exploiting the intrinsic sensitivity and noise immunity of the CRDS technique, we show that liquid absorption can be detected down to a level that is nearly a factor of 20 above the shot noise limit. We provide a thorough comparison between the experimental results and various noise contributions and address different expressions that can be used to calculate the shot noise equivalent absorbance. As a proof of principle, polyamine detection in aqueous solutions is carried out demonstrating a minimum detectable absorbance of 1.8×10(-7) Hz(-1/2), which, to our knowledge, is the best sensitivity limit reported to date for evanescent-wave sensors.

Split-mode fiber Bragg grating sensor for high-resolution static strain measurements.

We demonstrate a strain sensor with very high sensitivity in the static and low frequency regime based on a fiber ring cavity that includes a π phase-shifted fiber Bragg grating. The grating acts as a partial reflector that couples the two counter-propagating cavity modes, generating a splitting of the resonant frequencies. The presence of a sharp transition within the π phase-shifted fiber Bragg grating's spectral transmittance makes this frequency splitting extremely sensitive to length, temperature, and the refractive index of the fiber in the region where the grating is written. The splitting variations caused by small mechanical deformations of the grating are tracked in real time by interrogating a cavity resonance with a locked-carrier scanning-sideband technique. The measurable strain range and bandwidth are characterized, and a resolution of 320 pϵ/Hz(1/2) at 0 Hz is experimentally demonstrated, the highest achieved to date with a fiber Bragg grating sensor.