6 research outputs found
Evaluation of appendicitis risk prediction models in adults with suspected appendicitis
Background
Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis.
Methods
A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis).
Results
Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent).
Conclusion
Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified
Microwave-Promoted Catalyst- and Solvent-Free Aza-Diels–Alder Reaction of Aldimines with 6-[2-(Dimethylamino)vinyl]-1,3-dimethyluracil
A microwave-promoted aza-Diels–Alder reaction
between 6-[2-(dimethylamino)vinyl]-1,3-dimethyluracil
and aldimines has been developed for the construction of dihydropyrido[4,3-<i>d</i>]pyrimidines. Urea is effectively employed as an environmentally
benign source of ammonia in the absence of any catalyst or solvent.
The key step in the reaction is in situ generation and trapping of
the reactive aldimine formed from urea and aldehyde by the diene system
of the uracil. The reaction is clean, and excellent yields are obtained
in a matter of a few minutes
Air-Stable Surface-Passivated Perovskite Quantum Dots for Ultra-Robust, Single- and Two-Photon-Induced Amplified Spontaneous Emission
We demonstrate ultra-air- and photostable
CsPbBr<sub>3</sub> quantum
dots (QDs) by using an inorganic–organic hybrid ion pair as
the capping ligand. This passivation approach to perovskite QDs yields
high photoluminescence quantum yield with unprecedented operational
stability in ambient conditions (60 ± 5% lab humidity) and high
pump fluences, thus overcoming one of the greatest challenges impeding
the development of perovskite-based applications. Due to the robustness
of passivated perovskite QDs, we were able to induce ultrastable amplified
spontaneous emission (ASE) in solution processed QD films not only
through one photon but also through two-photon absorption processes.
The latter has not been observed before in the family of perovskite
materials. More importantly, passivated perovskite QD films showed
remarkable photostability under continuous pulsed laser excitation
in ambient conditions for at least 34 h (corresponds to 1.2 ×
10<sup>8</sup> laser shots), substantially exceeding the stability
of other colloidal QD systems in which ASE has been observed
Perovskite Nanocrystals as a Color Converter for Visible Light Communication
Visible light communication
(VLC) is an emerging technology that
uses light-emitting diodes (LEDs) or laser diodes for simultaneous
illumination and data communication. This technology is envisioned
to be a major part of the solution to the current bottlenecks in data
and wireless communication. However, the conventional lighting phosphors
that are typically integrated with LEDs have limited modulation bandwidth
and thus cannot provide the bandwidth required to realize the potential
of VLC. In this work, we present a promising light converter for VLC
by designing solution-processed CsPbBr<sub>3</sub> perovskite nanocrystals
(NCs) with a conventional red phosphor. The fabricated CsPbBr<sub>3</sub> NC phosphor-based white light converter exhibits an unprecedented
modulation bandwidth of 491 MHz, which is ∼40 times greater
than that of conventional phosphors, and the capability to transmit
a high data rate of up to 2 Gbit/s. Moreover, this perovskite-enhanced
white light source combines ultrafast response characteristics with
a high color rendering index of 89 and a correlated color temperature
of 3236 K, thereby enabling dual VLC and solid-state lighting functionalities
Surface Restructuring of Hybrid Perovskite Crystals
Hybrid
perovskite crystals have emerged as an important class of
semiconductors because of their remarkable performance in optoelectronics
devices. The interface structure and chemistry of these crystals are
key determinants of the device’s performance. Unfortunately,
little is known about the intrinsic properties of the surfaces of
perovskite materials because extrinsic effects, such as complex microstructures,
processing conditions, and hydration under ambient conditions, are
thought to cause resistive losses and high leakage current in solar
cells. We reveal the intrinsic structural and optoelectronic properties
of both pristinely cleaved and aged surfaces of single crystals. We
identify surface restructuring on the aged surfaces (visualized on
the atomic-scale by scanning tunneling microscopy) that lead to compositional
and optical bandgap changes as well as degradation of carrier dynamics,
photocurrent, and solar cell device performance. The insights reported
herein clarify the key variables involved in the performance of perovskite-based
solar cells and fabrication of high-quality surface single crystals,
thus paving the way toward their future exploitation in highly efficient
solar cells