Intensity noise in difference frequency generation-based tunable femtosecond MIR sources

We characterize the intensity noise of two mid-infrared (MIR) ultrafast tunable (3.5-11 μm) sources based on difference frequency generation (DFG). While both sources are pumped by a high repetition rate Yb-doped amplifier delivering 200 μJ 300 fs at a central wavelength of 1030 nm, the first is based on intrapulse DFG (intraDFG), and the second on DFG at the output of an optical parametric amplifier (OPA). The noise properties are assessed through measurement of the relative intensity noise (RIN) power spectral density and pulse-to-pulse stability. The noise transfer mechanisms from the pump to the MIR beam is empirically demonstrated. As an example, improving the pump laser noise performance allows reduction of the integrated RIN (IRIN) of one of the MIR source from 2.7% RMS down to 0.4% RMS. The intensity noise is also measured at various stages and in several wavelength ranges in both laser system architectures, allowing us to identify the physical origin of their variation. This study presents numerical values for the pulse to pulse stability, and analyze the frequency content of the RINs of particular importance for the design of low-noise high repetition rate tunable MIR sources and future high performance time-resolved molecular spectroscopy experiments.

Incidence and predictors of transthyretin cardiac amyloidosis in patients with degenerative aortic stenosis

Background

The approval of new therapies for treating transthyretin (TTR) cardiac amyloidosis has led to significant interest in identifying patients at high risk for this disease. Investigators have identified a correlation between severe degenerative aortic stenosis (AS) and TTR cardiac amyloidosis in older patients, with several studies finding up to 20% of patients who undergo transcatheter aortic valve replacement (TAVR) having TTR cardiac amyloidosis. These initial TAVR studies were conducted when TAVR was performed almost exclusively in high surgical risk populations. Therefore, the true incidence of TTR cardiac amyloidosis in an all-comers with severe degenerative AS referred for TAVR is unknown.

Purpose

To identify the true burden of TTR cardiac amyloidosis in a contemporary population of severe degenerative AS undergoing TAVR screening.

Methods

All patients ≥70 years with severe native valve degenerative AS seen in a multidisciplinary valve clinic were referred for technetium-99m pyrophosphate cardiac scintigraphy (PYP scan) for evaluation of cardiac amyloidosis. Diagnosis was made via combination of planar grade and heart to contralateral lung ratio, confirmed on single positron emission computed tomography/computed tomography (SPECT/CT). Patients with a positive PYP scan were referred to a heart failure clinic where they underwent testing for AL amyloidosis.

Results

Over a 10 month period, 247 patients seen in valve clinic underwent a PYP scan. Of this cohort, 203 patients ultimately underwent TAVR, 15 surgical aortic valve replacement, and 2 balloon valvuloplasty with 27 patients having not yet undergone a procedure. The positivity rate was 4% (10/247) with 1 patient having an equivocal result. The patients with a positive PYP scan had higher rate of low-flow low-gradient (LFLG) AS (64% vs 29%, p=0.006) and classical LFLG AS (27% vs 8%, p=0.02). Echocardiographic measures associated with a positive PYP scan include a lower global longitudinal strain (−10.0% vs −16.1%, p=0.008), lower average e' (4.5 vs 6.5, p=0.003), and an increased E/A ratio (1.8 vs 1.1, p=0.018).

Conclusions

The incidence of TTR amyloidosis in a contemporary, severe AS population ≥70 years undergoing TAVR screening appears much lower than previously described in the literature. Echocardiographic traits may be able to predict which patients with severe AS should undergo evaluation for TTR cardiac amyloidosis.

Funding Acknowledgement

Type of funding sources: None.

Inline amplification of mid-infrared intrapulse difference frequency generation

We demonstrate an ultrafast mid-infrared source architecture that implements both intrapulse difference frequency generation (iDFG) and further optical parametric amplification (OPA), in an all-inline configuration. The source is driven by a nonlinearly compressed high-energy Yb-doped-fiber amplifier delivering 7.4 fs pulses at a central wavelength of 1030 nm, at a repetition rate of 250 kHz. It delivers 1 µJ, 73 fs pulses at a central wavelength of 8 µm, tunable over more than one octave. By enrolling all the pump photons in the iDFG process and recycling the long wavelength pump photons amplified in the iDFG in the subsequent OPA, we obtain an unprecedented overall optical efficiency of 2%. These performances, combining high energy and repetition rate in a very simple all-inline setup, make this technique ideally suited for a growing number of applications, such as high harmonic generation in solids or two-dimensional infrared spectroscopy experiments.

Enhanced intrapulse difference frequency generation in the mid-infrared by a spectrally dependent polarization state

We present a technique to optimize the intrapulse difference frequency generation efficiency for mid-infrared generation. The approach employs a multi-order wave plate that is designed to selectively rotate the polarization state of the incoming spectral components on the relevant orthogonal axes for subsequent nonlinear interaction. We demonstrate a significant increase of the mid-infrared average power generated, of a factor ≥2.5 compared with the conventional scheme, owing to an optimally distributed number of photons enrolled in the difference frequency generation process.

Two Epidemics and a Pandemic: The Collision of Prescription Drug Misuse and Racism during COVID-19

The present study investigated the relationship between perceived racial discrimination and prescription drug misuse (PDM) among Asian, Black, and Latinx Americans during the COVID-19 crisis. U.S. racial/ethnic minorities may have been uniquely affected by two national and one global pandemic: the opioid crisis, racism, and COVID-19. Opioid death rates increased among many groups prior to the pandemic. This country witnessed an increase in racialized acts against people of color across the spectrum in the spring and summer months of the world's COVID-19 outbreak. While studies have shown a clear link between perceived racial discrimination and substance abuse outside of the global pandemic, no identified studies have done so against the backdrop of a global health pandemic. Separate hierarchical regressions revealed a significant association between perceived racial discrimination and PDM for Black Americans, Asian Americans, and Latinx individuals. Findings build on the scant literature on PDM in diverse samples and establish a relationship between perceived racial discrimination and PDM, as previously identified for other abused substances. Future post-pandemic substance misuse interventions should consider the influence of perceived racial discrimination as they help individuals recover from the aftermath of this stressful trifecta.

1364 Quality Control of Discharge Summaries for Endocrine Surgery Patients; A Closed Loop Audit

Aim

A patient's discharge summary (TTO) should be accurate. Most of them are conducted by junior doctors at the beginning of their medical training. The information mentioned in a TTO ensures patient safety, continuity of care as well as correct clinical coding for the NHS. Therefore, a re-audit was designed to check the quality of the discharge summaries of endocrine surgical patients In Nottingham City Hospital i.e., the type of operation, diagnosis, or postoperative instructions.

Method

The first cycle included all the TTOs for the endocrine surgical patients operated from April 2018 to November 2018. Then we re-audited those who had endocrine surgeries from April 2019 to November 2019. NOTIS e-TTO, Bluespier theatre lists and Medway were used to retrieve the data. All general surgery patients were excluded.

Results

142 and 104 patients TTOs were included in each audit cycle, respectively. Type of operation was improved from 84% to 95% in the second cycle. Correct diagnosis was reported from 68% to 72% in the second cycle audit.

Conclusions

The introduction of electronic operation notes in our practice improved the correct clinical coding for the type of operation mentioned in the TTO. The accuracy of correct diagnosis remains suboptimal. Therefore, education of junior doctors and an idea of double-checking from a more senior colleague should be assessed.

746 Single-Centre Experience with Three Metallic Ureteric Stents (Allium URS, Memokath-051 and Resonance) for Chronic Ureteric Obstruction

Aim

To evaluate efficacy of Allium URS, Memokath 051 and Resonance metallic ureteric stents as an alternative to polymer stents/nephrostomy in managing chronic ureteric obstruction (CUO).

Method

Retrospective analysis of consecutive patients with CUO managed with Allium URS, Memokath-051 or Resonance (September 2015/July 2020). Baseline patient variables (age, gender, underlying aetiology, ASA) and stricture characteristics (length, level, continuity) were recorded. Intra- and post-operative clinical and radiological follow-up assessments at 6 weeks, 3 months and then every 6 months, as well as any emergency attendances, were reviewed for placement success, stent complications, serum creatinine, and mortality. Outcomes included placement success rate, functional stent survival, and mean renal function.

Results

Overall, 129 stent insertion episodes (SIEs) (Allium URS: 23, Memokath 051: 48, Resonance: 58) occurred in 76 patients (Allium URS: 16; Memokath-051: 31; Resonance: 29). Placement success was high (Allium URS: 95.7%; Memokath-051 and Resonance: both 100%). Median functional stent survival was 11.4 months for Allium URS, 5.5 months for Memokath-051 and 11.7 months for Resonance. 47.8% of Allium URS SIEs (11/23), 64.6% of Memokath-051 SIEs (31/48) and 19% of Resonance SIEs (11/58) experienced complication (most frequently obstruction followed by migration and infection). There were no complications for Resonance SIEs for benign indication. In the first year following SIE, serum creatinine ranged from +21.3% to + 46.7% for Allium URS, -7.8% to + 8.9% for Memokath-051, and -9.4% to + 27.3% for Resonance.

Conclusions

Allium URS, Memokath 051 and Resonance metallic ureteric stents are all viable management options of CUO. Resonance was particularly efficacious for patients with benign aetiology.

Benefits of tafamidis in patients with advanced transthyretin amyloid cardiomyopathy

Background

In the Tafamidis in Transthyretin Cardiomyopathy Clinical Trial (ATTR-ACT), tafamidis was shown to be an effective treatment for patients with transthyretin amyloid cardiomyopathy (ATTR-CM). Further assessment of the efficacy of tafamidis in patients with more advanced ATTR-CM would aid treatment decisions.

Purpose

To characterize the benefits of tafamidis in patients with advanced ATTR-CM.

Methods

In ATTR-ACT, ATTR-CM patients were randomized to tafamidis (n=264) or placebo (n=177) for 30 months. Efficacy outcomes included all-cause mortality and frequency of cardiovascular (CV)-related hospitalisations. Key secondary endpoints were change from baseline to Month 30 in 6MWT distance and KCCQ-OS score. Efficacy assessments in NYHA Class III patients at baseline (n=141) were a pre-specified analysis. In a post-hoc analysis, mortality and CV-related hospitalizations were assessed in all patients grouped into quartiles of increasing disease severity based on 6MWT distance at baseline. Longer-term all-cause mortality (as of 1 Aug 2019) was assessed in NYHA Class III patients utilizing data from ATTR-ACT patients who enrolled in a long-term, extension study (LTE) and continued treatment with higher dose tafamidis (n=55; median treatment duration 51.6 months); or, if previously treated with placebo, started tafamidis treatment (placebo/tafamidis; n=63 [50.1 months]).

Results

In advanced ATTR-CM patients (NYHA Class III), tafamidis reduced the risk of death (HR [95% CI] 0.837, [0.541, 1.295], P=0.4253), and the decline in 6MWT distance (LS mean [SE], 31.6 (22.1) m; P=0.1526) and KCCQ-OS score (LS mean [SE], 13.1 (5.0); P=0.0090), vs placebo. Paradoxically, there was a higher frequency of CV-related hospitalizations with tafamidis (RR [95% CI] vs placebo, 1.411 [1.048, 1.900]). In all patients by 6MWT quartile, CV-related hospitalizations/year with tafamidis and placebo increased with disease severity, with the exception that placebo-treated patients in the highest severity quartile had fewer CV-related hospitalisations (0.73) than those in the third quartile (0.92). Mortality with tafamidis and placebo increased, and was greater with placebo, in every quartile (Figure). Survival (NYHA Class III patients in ATTR-ACT and LTE) was improved with high dose tafamidis with longer term follow-up (HR vs placebo/tafamidis [95% CI], 0.6569 [0.4175, 1.0336]; P=0.0692).

Conclusions

These analyses, including longer-term follow-up, demonstrate that patients with advanced ATTR-CM benefit from tafamidis. The decrease in CV-related hospitalisations in more severe patients treated with placebo suggests that the comparatively greater hospitalisation frequency in NYHA Class III patients treated with tafamidis is a consequence of their lower mortality rate.

Figure 1

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): This study was sponsored by Pfizer

Abdominal adiposity assessed using CT angiography associates with acute kidney injury after trans-catheter aortic valve replacement

AIM

To determine if there is an association between area-based visceral abdominal adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAT), and abdominal circumference measured on computed tomography (CT) angiography before trans-catheter aortic valve replacement (TAVR) and post-TAVR acute kidney injury (AKI).

MATERIALS AND METHODS

In this retrospective cohort study of 106 TAVR patients, SAT and VAT areas and abdominal circumference was measured on a single CT section at L4 vertebral level. Univariate comparisons between patients who did and did not develop AKI were undertaken for radiological measurements. Multivariable logistic regression was used to assess association between CT measurements and the development of post-TAVR AKI.

RESULTS

Post-TAVR AKI occurred in 20 of 106 patients (19%). In univariate comparisons, body mass index (BMI) did not differ significantly between patients who did and did not develop AKI (p=0.14); however, VAT+SAT (443.2±163.7 versus 351±168.7 cm²; p=0.03), VAT (213.9±110.6 versus 153.9±96.1 cm²; p=0.03), and outer abdominal circumference (100.2±14.4 cm versus 91.8±13.3 cm; p=0.02) were significantly higher in the patients who did not develop post-TAVR AKI. These three measures on pre-TAVR CT angiogram remained significantly associated with reduced post-TAVR AKI with a lower incidence of post-TAVR AKI after multivariable adjustment for pre-TAVR estimated glomerular filtration rate and patient height (p<0.05).

CONCLUSION

This study found that increased abdominal obesity as assessed by measures on pre-TAVR CT angiogram is associated with a significantly lower incidence of AKI.

CEP-stable high-energy ytterbium-doped fiber amplifier

We report on the carrier-envelope phase (CEP) stabilization of a Yb-doped fiber amplifier system delivering 30 μJ pulses at 100 kHz repetition rate. A single-shot, every-shot measurement of the CEP stability based on a simple f-2f interferometer is performed, yielding a CEP standard deviation of 320 mrad rms over 1 s. Long-term stability is also assessed, with 380 mrad measured over 1 h. This level of performance is allowed by a hybrid architecture, including a passively CEP-stabilized front-end based on difference frequency generation and an active CEP stabilization loop for the fiber amplifier system, acting on a telecom-grade integrated LiNbO3 phase modulator. Together with recent demonstrations of temporal compression down to the few-cycle regime, the presented results demonstrate the relevance of the Yb-doped high repetition rate laser for attoscience.

High-power two-cycle ultrafast source based on hybrid nonlinear compression

We demonstrate a hybrid dual-stage nonlinear compression scheme, which allows the temporal compression of 330 fs-pulses down to 6.8 fs-pulses, with an overall transmission of 61%. This high transmission is obtained by using a first compression stage based on a gas-filled multipass cell, and a second stage based on a large-core gas-filled capillary. The source output is fully characterized in terms of spectral, temporal, spatial, and short- and long-term stability properties. The system's compactness, stability, and high average power makes it ideally suited to drive high photon flux XUV sources through high harmonic generation.

Universal intracellular biomolecule delivery with precise dosage control

Intracellular delivery of mRNA, DNA, and other large macromolecules into cells plays an essential role in an array of biological research and clinical therapies. However, current methods yield a wide variation in the amount of material delivered, as well as limitations on the cell types and cargoes possible. Here, we demonstrate quantitatively controlled delivery into a range of primary cells and cell lines with a tight dosage distribution using a nanostraw-electroporation system (NES). In NES, cells are cultured onto track-etched membranes with protruding nanostraws that connect to the fluidic environment beneath the membrane. The tight cell-nanostraw interface focuses applied electric fields to the cell membrane, enabling low-voltage and nondamaging local poration of the cell membrane. Concurrently, the field electrophoretically injects biomolecular cargoes through the nanostraws and into the cell at the same location. We show that the amount of material delivered is precisely controlled by the applied voltage, delivery duration, and reagent concentration. NES is highly effective even for primary cell types or different cell densities, is largely cargo agnostic, and can simultaneously deliver specific ratios of different molecules. Using a simple cell culture well format, the NES delivers into >100,000 cells within 20 s with >95% cell viability, enabling facile, dosage-controlled intracellular delivery for a wide variety of biological applications.

Nonlinear pulse compression based on a gas-filled multipass cell

We demonstrate nonlinear temporal compression of a high-energy Yb-doped fiber laser source in a multipass cell filled with argon. The 160 μJ 275 fs input pulses are compressed down to 135 μJ 33 fs at the output, corresponding to an overall transmission of 85%. We also analyze the output beam, revealing essentially no space-time couplings. We believe this technique can be scalable to higher pulse energies and shorter pulse durations, enabling access to a wider parameter range for a large variety of ultrafast laser sources.

An incidental finding of severe hyperferritinaemia: a lesson to be learned

Haemophagocytic lymphohistiocytosis is a rare, under-recognised and often misdiagnosed condition, characterised by a hyperinflammatory response to malignancy or infection. In this case, the cause was a bone marrow isolated anaplastic large cell lymphoma without radiological evidence of systemic disease, a phenomenon rarely described. We present the case of a previously fit and well 64-year-old female who presented on multiple occasions to primary and secondary care in a stable condition with an undifferentiated illness with the only consistent feature being a marked, unexplained hyperferritinaemia. The history highlights the importance of ferritin as a marker of phagocytic activity and how severely high levels, even in the well patient, should prompt early bone marrow biopsy. The prognosis of haemophagocytic lymphohistiocytosis is invariably poor as the condition is usually secondary to a serious underlying disease such as haematological malignancy as in this case. The diagnostic difficulty often leads to delayed recognition and treatment.

How long can a waiting list be?

Aims and Method

Quantifying the relationship between waiting time and clinic attendance in child and adolescent psychiatry would allow better estimation of the resources needed to eliminate waiting lists in specific initiatives. All cases on a waiting list were sent a questionnaire, return of the questionnaire being necessary for an appointment to be made. Those who did not return the questionnaire or did not attend were contacted and a reason obtained whenever possible. The data were analysed using Cox regression.

Results

Most who did not return their questionnaires had been waiting less than four weeks or longer than 30 weeks. Questionnaire return seemed a good estimate of intention to attend. Other factors improving questionnaire return were younger patient age, previous experience of the service, a clear common reason for referral, and a non-general practitioner referral source.

Clinical Implications

Waiting lists in child and adolescent psychiatry may have a natural ‘endpoint’ at 30 weeks beyond which families give up, while waiting lists of less than one-month may be too short to lose transient problems. Failure to include this and other indicators of non-attendance may lead to overestimates of resources needed to remove queues for treatment. Questionnaires may be useful in identifying those intending to attend.

Neonatal Acute Kidney Injury: A Survey of Neonatologists' and Nephrologists' Perceptions and Practice Management

BACKGROUND

Neonatal acute kidney injury (AKI) occurs in 40 to 70% of critically ill neonatal intensive care admissions. This study explored the differences in perceptions and practice variations among neonatologists and pediatric nephrologists in diagnostic criteria, management, and follow-up of neonatal AKI.

METHODS

A survey weblink was emailed to nephrologists and neonatologists in Australia, Canada, New Zealand, India, and the United States. Questions consisted of demographic and unit practices, three clinical scenarios assessing awareness of definitions of neonatal AKI, knowledge, management, and follow-up practices.

RESULTS

Many knowledge gaps among neonatologists, and to a lesser extent, pediatric nephrologists were identified. Neonatologists were less likely to use categorical definitions of neonatal AKI (p < 0.00001) or diagnose stage 1 AKI (p < 0.00001) than pediatric nephrologists. Guidelines for creatinine monitoring for nephrotoxic medications were reported by 34% (aminoglycosides) and 62% (indomethacin) of respondents. Nephrologists were more likely to consider follow-up after AKI than neonatologists (p < 0.00001). Also, 92 and 86% of neonatologists and nephrologists, respectively, reported no standardization or infrastructure for long-term renal follow-up.

CONCLUSION

Neonatal AKI is underappreciated, particularly among neonatologists. A lack of evidence on neonatal AKI contributes to this variation in response. Therefore, dissemination of current knowledge and areas for research should be the priority.