Advanced life support interventions during intra-operative cardiac arrest among adults as reported to the 7th National Audit Project of the Royal College of Anaesthetists.

BACKGROUND: Few existing resuscitation guidelines include specific reference to intra-operative cardiac arrest, but its optimal treatment is likely to require some adaptation of standard protocols. METHODS: We analysed data from the 7th National Audit Project of the Royal College of Anaesthetists to determine the incidence and outcome from intra-operative cardiac arrest and to summarise the advanced life support interventions reported as being used by anaesthetists. RESULTS: In the baseline survey, > 50% of anaesthetists responded that they would start chest compressions when the non-invasive systolic pressure was < 40-50 mmHg. Of the 881 registry patients, 548 were adult patients (aged > 18 years) having non-obstetric procedures under the care of an anaesthetist, and who had arrested during anaesthesia (from induction to emergence). Sustained return of spontaneous circulation was achieved in 425 (78%) patients and 338 (62%) were alive at the time of reporting. In the 365 patients with pulseless electrical activity or bradycardia, adrenaline was given as a 1 mg bolus in 237 (65%). A precordial thump was used in 14 (3%) patients, and although this was associated with return of spontaneous circulation at the next rhythm check in almost three-quarters of patients, in only one of these was the initial rhythm shockable. Calcium (gluconate or chloride) and 8.4% sodium bicarbonate were given to 51 (9%) and 25 (5%) patients, but there were specific indications for these treatments in less than half of the patients. A thrombolytic drug was given to 5 (1%) patients, and extracorporeal cardiopulmonary resuscitation was used in 9 (2%) of which eight occurred during cardiac procedures. CONCLUSIONS: The specific characteristics of intra-operative cardiac arrest imply that its optimal treatment requires modifications to standard advanced life support guidelines.

Definition of diaphragmatic sleep disordered breathing and clinical meaning in Duchenne muscular dystrophy.

BACKGROUND: Diaphragmatic sleep disordered breathing (dSDB) has been recently identified as sleep dysfunction secondary to diaphragmatic weakness in Duchenne muscular dystrophy (DMD). However, scoring criteria for the identification of dSDB are missing.This study aimed to define and validate dSDB scoring criteria and to evaluate whether dSDB severity correlates with respiratory progression in DMD. METHODS: Scoring criteria for diaphragmatic apnoea (dA) and hypopnoeas (dH) have been defined by the authors considering the pattern observed on cardiorespiratory polygraphy (CR) and the dSDB pathophysiology.10 sleep professionals (physiologists, consultants) blinded to each other were involved in a two-round Delphi survey to rate each item of the proposed dSDB criteria (Likert scale 1-5) and to recognise dSDB among other SDB. The scorers' accuracy was tested against the authors' panel.Finally, CR previously conducted in DMD in clinical setting were rescored and diaphragmatic Apnoea-Hypopnoea Index (dAHI) was derived. Pulmonary function (forced vital capacity per cent of predicted, FVC%pred), overnight oxygen saturation (SpO2) and transcutaneous carbon dioxide (tcCO2) were correlated with dAHI. RESULTS: After the second round of Delphi, raters deemed each item of dA and dH criteria as relevant as 4 or 5. The agreement with the panel in recognising dSDB was 81%, kappa 0.71, sensitivity 77% and specificity 85%.32 CRs from DMD patients were reviewed. dSDB was previously scored as obstructive. The dAHI negatively correlated with FVC%pred (r=-0.4; p<0.05). The total number of dA correlated with mean overnight tcCO2 (r 0.4; p<0.05). CONCLUSIONS: dSDB is a newly defined sleep disorder that correlates with DMD progression. A prospective study to evaluate dSDB as a respiratory measure for DMD in clinical and research settings is planned.

Quantifying Infiltration for Quality Control in Printed Mesoscopic Perovskite Solar Cells: A Microscopic Perspective.

Mesoscopic carbon-based perovskite solar cells (CPSCs) are often cited as a potential frontrunner to perovskite commercialization. Infiltration, the extent to which perovskite fills the mesoporous scaffold, is critical for optimum performance and stability. However, infiltration data are usually presented as qualitative photographic comparisons of samples with extreme infiltration variation. This work examines how small infiltration defects impact performance using an optical microscopy examination of the base TiO2 layer to identify issues and develop targeted techniques for infiltration enhancement. Critically, the uninfiltrated area at the base of the stack was found to correlate well with PCE across multiple batches of varied print quality and ZrO2 thickness. Through reduction of mesh mark defects and improvement of print quality in the ZrO2 and carbon layers, a champion PCE of 15.01% is attained. It follows that this facile, multiscaled, nondestructive technique could enable targeted performance enhancement and quality control in future scale-up initiatives.

Chemoselective Staudinger Reactivity of Bis(azido)phosphines Supported with a π-Donating Imidazolin-2-iminato Ligand.

Synthesis and characterization of new P(III) and P(V) bis(azido)phosphines/phosphoranes supported by an N,N'-bis(2,6-diisopropylphenyl) imidazolin-2-iminato (IPrN) ligand and their reactivity with various secondary and tertiary phosphines result in the formation of chiral and/or asymmetric mono(phosphinimino)azidophosphines via the Staudinger reaction. The reaction of IPrNP(N3)2 (2) or IPrNP(S)(N3)2 (4S) with an excess of tertiary phosphine resulted in the chemoselective formation of IPrNP(N3)(NPMe3) (7) or IPrNP(S)N3(NPR3) (5R), respectively. The chemoselective Staudinger reactivity was also observed in reactions using a secondary phosphine (HPCy2) to produce IPrNP(S)N3[NP(H)Cy2] (6a), which exists in equilibrium with a tautomeric IPrNP(S)N3[N(H)PCy2] form (6b), as confirmed by 31P-31P nuclear Overhauser effect spectroscopy (NOESY). Density functional theory (DFT) calculations point to a combination of energetically unfavorable lowest unoccupied molecular orbitals (LUMOs) and the accumulation of increasing negative charge at the terminal azido-nitrogen upon a single azide-to-phosphinimine conversion that gave rise to the observed chemoselectivity.

Role of overnight oximetry in assessing the severity of obstructive sleep apnoea in typically developing children: a multicentre study.

BACKGROUND AND OBJECTIVE: Cardiorespiratory polygraphy (CRP) is the predominant technology used to diagnose obstructive sleep apnoea (OSA) in tertiary centres in the UK. Nocturnal pulse oximetry (NPO) is, however, cheaper and more accessible. This study evaluated the ability of NPO indices to predict OSA in typically developing (TD) children. METHODS: Indices from simultaneous NPO and CRP recordings were compared in TD children (aged 1-16 years) referred to evaluate OSA in three tertiary centres. OSA was defined as an obstructive apnoea-hypopnoea index (OAHI) ≥1 event/hour. Receiver operating characteristic curves assessed the diagnostic accuracy of NPO indices including ODI3 (3% Oxygen Desaturation Index, ODI4 (4% Oxygen Desaturation Index), delta 12 s index and minimum oxygen saturation. Two-by-two tables were generated to determine the sensitivities and specificities of whole number cut-off values for predicting OAHIs ≥1, 5 and 10 events/hour. RESULTS: Recordings from 322 TD children, 197 male (61.2%), median age 4.9 years (range 1.1-15.6), were reviewed. OAHI was ≥1/hour in 144 (44.7%), ≥5/hour in 61 (18.9%) and ≥10/hour in 28 (8.7%) cases. ODI3 and ODI4 had the best diagnostic accuracy. ODI3 ≥7/hour and ODI4 ≥4/hour predicted OSA in TD children with sensitivities/specificities of 57.6%/85.4% and 46.2%/91.6%, respectively. ODI3 ≥8/hour was the best predictor of OAHI ≥5/hour (sensitivity 82.0%, specificity 84.3%). CONCLUSION: Raised ODI3 and ODI4 predict OSA in TD children with high specificity but variable sensitivity. NPO may be an alternative to diagnose moderate-severe OSA if access to CRP is limited. Low sensitivities to detect mild OSA mean that confirmatory CRP is needed if NPO is normal.

Revealing The Morphology of Ink and Aerosol Jet Printed Palladium-Silver Alloys Fabricated from Metal Organic Decomposition Inks.

Palladium films hold signicance due to their remarkable affinity for hydrogen diffusion, rendering them valauble for the seperation and purification of hydrogen in membrane reactors. However, palladium is expensive, and its films can become brittle after only a few cycles of hydrogen separation. Alloying with silver has been shown to overcome the problem of palladium embrittlement. Palladium-silver films have been produced via several methods but all have drawbacks, such as difficulties controlling the alloy composition. This study explores two promising jet printing methods: Inkjet and Aerosoljet. Both methods offer potential advantages such as direct patterning, which reduces waste, enables thin film production, and allows for the control of alloy composition. For the first time, palladium-silver alloys have been produced via inkjet printing using a palladium-silver metal organic decomposition (MOD) ink, which alloys at a temperature of 300 °C with nitrogen. Similarly, this study also demonstrates a pioneering approach for Aerosol Jet printing, showing the potential of a novel room-temperature method, for the deposition of palladium-silver MOD inks. This low temperature approach is considered an important development as palladium-silver MOD inks are originally designed for deposition on heated substrates.

Supporting the capacities and knowledge of smallholder farmers in Kenya for sustainable agricultural futures: a Citizen Science pilot project.

Sub-Saharan Africa is often presented as the continent most vulnerable to climatic change with major repercussions for food systems. Coupled with high rates of population growth, continued food insecurity and malnutrition, thus the need to enhance food production across the continent is seen as a major global imperative. We argue here, however, that current models of agricultural development in Eastern Africa frequently marginalise critical smallholder knowledge from the process of future agricultural design due to a lack of a methodological tools for engagement. This paper addresses this by outlining a potential means to capture and share locally produced agronomic information on a large scale. We report on a 'Citizen Science' pilot study that worked with smallholder farmers in Elgeyo-Marakwet County, Western Kenya, to co-design a mobile application using the well-developed Sapelli platform that easily allows farmers to identify, record and geolocate cropping patterns and challenges at multiple stages in the agricultural calendar using their own understanding. The pilot project demonstrated the technical and epistemological benefits of co-design, the abilities of smallholder farmers to co-design and use smartphone applications, and the potential for such technology to produce and share valuable agricultural and ecological knowledge in real time. Proof-of-concept data illustrates opportunities to spatially and temporally track and respond to challenges related to climate, crop disease and pests. Such work expounds how smallholder farmers are a source of largely untapped ecological and agronomic expert knowledge that can, and should, be harnessed to address issues of future agricultural resilience and food system sustainability.

Grinding of silicon carbide for optical surface fabrication. Part II. Subsurface damage.

This paper is the second part of a study of the grinding of three different grades of silicon carbide (SiC) under the same conditions. In this paper, subsurface damage is analyzed using magnetorheological finishing (MRF). The MRF ribbon is brought into contact with the surface and allowed to dwell for different lengths of time to produce dimples or spots at different depths. The roughness parameters are evaluated at the base of the spots. As the spot depth increases the roughness parameters decrease, eventually saturating at a steady-state value. The depth at which saturation occurs is much greater than the initial peak-to-value roughness of the surface and is therefore assumed to be correlated to the depth of subsurface damage in the material. Estimates of the damage depth are comparable to other estimates given in the literature. The validity of this technique is assessed across different grades of SiC under different grinding conditions, and limitations are identified. The study shows that the microstructure of the SiC grade is a major factor that affects the validity of the technique. The technique is suitable for SiC grades that have a more homogeneous microstructure such as chemical vapor deposited or chemical vapor composite grades. The presence of porosity as in the direct sintered grade, or the presence of a secondary phase, for example, silicon in the reaction-bonded and silicon-infiltrated grades, could hinder the technique from providing conclusive results.

Unravel the Tangle: Atomistic Insight into Ultrahigh Curcumin-Loaded Polymer Micelles.

Amphiphilic ABA-triblock copolymers, comprised of poly(2-oxazoline) and poly(2-oxazine), can solubilize poorly water-soluble molecules in a structure-dependent manner forming micelles with exceptionally high drug loading. All-atom molecular dynamics simulations are conducted on previously experimentally characterized, curcumin-loaded micelles to dissect the structure-property relationships. Polymer-drug interactions for different levels of drug loading and variation in polymer structures of both the inner hydrophobic core and outer hydrophilic shell are investigated. In silico, the system with the highest experimental loading capacity shows the highest number of drug molecules encapsulated by the core. Furthermore, in systems with lower loading capacity outer A blocks show a greater extent of entanglement with the inner B blocks. Hydrogen bond analyses corroborate previous hypotheses: poly(2-butyl-2-oxazoline) B blocks, found experimentally to have reduced loading capacity for curcumin compared to poly(2-propyl-2-oxazine), establish fewer but longer-lasting hydrogen bonds. This possibly results from different sidechain conformations around the hydrophobic cargo, which is investigated by unsupervised machine learning to cluster monomers in smaller model systems mimicking different micelle compartments. Exchanging poly(2-methyl-2-oxazoline) with poly(2-ethyl-2-oxazoline) leads to increased drug interactions and reduced corona hydration; this suggests an impairment of micelle solubility or colloidal stability. These observations can help driving forward a more rational a priori nanoformulation design.

PEARS: A Web Tool for Fitting Time-Resolved Photoluminescence Decays of Perovskite Materials.

Time-resolved photoluminescence (TRPL) is a powerful tool to investigate charge carrier recombination processes in emissive materials. Perovskite materials are extremely promising for applications in solar cells; however, the interpretation of their TRPL is arduous due to the complicated nature of the recombination processes occurring in these materials. We present here the PErovskite cArrier Recombination Simulator (PEARS) web tool for effortlessly and quickly fitting TRPL of perovskite materials using advanced charge carrier recombination models, allowing for the extraction of recombination rate constants and trap state concentration. PEARS is flexible and can adapt to different situations, by ignoring recombination processes or fixing known parameters (e.g., the doping concentration). The tool is publicly available at https://pears-tool.herokuapp.com.

Liberal vs. restricted opioid prescribing following midurethral sling dataset.

Postoperative opioid prescribing has historically lacked information critical to balancing the pain control needs of the individual patient with our professional responsibility to judiciously prescribe these high-risk medications. This data evaluates pain control, satisfaction with pain control, and opioid utilization among patients undergoing isolated mid-urethral sling (MUS) randomized to one of two different opioid prescribing regimens. This study was registered on clinicaltrials.gov (NCT04277975). Women undergoing isolated MUS by a Female Pelvic Medicine and Reconstructive Surgery physician at a Penn State Health hospital from June 1, 2020 to November 22, 2021 were offered enrollment into this prospective, randomized, open-label, non-inferiority clinical trial. Participants gave informed consent and were enrolled by a member of the study team. Allocation was concealed to patient and study personnel until randomization on the day of surgery. Preoperatively, all participants completed baseline demographic and pain surveys including CSI-9, PCS, and Likert pain score (scale 0-10). Participants were randomized to either receive a standard prescription of ten 5 mg tablets oxycodone provided preoperatively (standard) or opioid prescription provided only upon patient request postoperatively (restricted). Randomization was performed by the study team surgeon using the REDCap randomization module on the day of surgery. Following MUS, subjects completed a daily diary for 1 week, i.e., postoperative day (POD) 0 through 7. Within the dairy, subjects provided the following information: average daily pain score, opioid use and amount of opioid utilized, other forms of pain management, satisfaction with pain control, perception of the amount of opioid prescribed, and need for pain management hospital/clinic visits. The online Prescription Drug Monitoring Program (PDMP) was queried for all patients to determine if prescriptions for opioids were filled during the postoperative period. The primary outcome was average postoperative day 1 pain score and an a priori determined margin of non-inferiority was set at 2 points. Secondary outcomes included whether subject filled an opioid prescription (indicated by the online PDMP), opioid use (yes/no), satisfaction with pain control (on a scale of 1= "much worse" to 5= "much better" than expected), and how subjects felt about the amount of opioid prescribed (on a scale of 1="prescribed far more" to 3="prescribed the right amount" to 5="prescribed far less" opioid than needed). 82 participants underwent isolated MUS placement and met inclusion criteria; 40 were randomized to the standard arm and 42 to the restricted group. Within this manuscript, we detail the data obtained from this randomized clinical trial and the methods utilized.

Factors Affecting Parent Treatment Decisions for Children with Autism Spectrum Disorders: A Brief Review.

Parents and caregivers of individuals with autism spectrum disorders (ASD) are faced with a vast array of treatment options, which vary greatly in evidence-based merits, and it is unclear what factors affect their final selections. Understanding the factors that influence family decisions can shed light on avenues for more effectively communicating the importance of selecting empirically supported treatments. In this article, we conducted a systematic literature review on how parents select evidence-based treatments for their children with ASD. We categorized treatment types using a combination of established resources, such as the National Standards Project (NSP), to determine the validity of research evidence for different ASD treatments. We reported the various treatment types, decision-making factors, and sources of recommendations across the literature, and compared those with earlier systematic literature reviews. The results of the present review indicate that parents' decisions are influenced by the accessibility of treatment, trust of practitioners, and alignment on factors such as parental values and the child's specific needs. We conclude with suggestions for practitioners and researchers on future research and wider adoption of evidence-based treatments (EBTs).

Cutaneous Perfusion Dynamics of the Lower Abdomen in Healthy Normal Weight, Overweight and Obese Women: Methods Development Using Infrared Thermography with Applications for Future Wound Management after Caesarean Section.

BACKGROUND: Evidence has shown an association between obesity and an increased risk of wound infection after caesarean section. This study was designed to examine if abdominal subcutaneous adiposity impacts upon cutaneous perfusion dynamics. METHODS: Mild cool challenge, followed by real-time video thermography, was developed to map the appearance of abdominal 'hot spots'. Correspondence of marked 'spots' with audible Doppler and colour and power Doppler ultrasound was performed. RESULTS: 60 healthy, afebrile, women (20-68 years; BMI 18.5-44 kg/m2) were recruited. Hot spot appearance consistently corresponded with audible Doppler sounds. Colour and power Doppler ultrasound revealed vessels at depths of 3-22 mm. No statistically significant interactions for BMI, abdominal circumference or environmental parameters were observed for hot spot count. The temperature of cold stimulus was significant for effects on spot count, but only for the first minute (p = 0.001). Thereafter, effects on spot numbers were not significant. CONCLUSIONS: Cutaneous 'perforator' mapping of the abdomen (via hot spot appearance) in healthy women, as a potential and future method for risk of perfusion-dependent wound healing complications, reveals that bedside mapping of skin perfusion is feasible over a short interval. Hot spot number was not influenced by BMI or indicators of central fat distribution (abdominal circumference) indicating variability in an individual's vascular anatomy. This study provides the underpinning methodology for personalised perfusion assessment after incisional surgery which may be a more reliable indicator of potential healing complications than body habitus as is currently the norm.

All-Printed Roll-to-Roll Perovskite Photovoltaics Enabled by Solution-Processed Carbon Electrode.

Perovskite photovoltaics have shown great promise in device efficiency but also the promise of scalability through solution-processed manufacture. Efforts to scale perovskites have been taken through printable mesoporous scaffolds and slot die coating of flexible substrates roll-to-roll (R2R). However, to date there has been no demonstration of entirely R2R-coated devices due to the lack of a compatible solution-processable back electrode; instead, high-value evaporated metal contacts are employed as a post process. Here, in this study, the combination of a low-temperature device structure and R2R-compatible solution formulations is employed to make a fully R2R printable device architecture overcoming interlayer incompatibilities and recombination losses. Therefore, the n-i-p device structure of SnO2 /perovskite/poly(3,4-ethylenedioxythiophene)/carbon is employed to form an ohmic contact between a p-type semiconductor and printable carbon electrode. In particular, the results show that the small-scale device efficiencies of 13-14% are achieved, matching the device performance of evaporated gold electrodes. Also, this entirely R2R-coated perovskite prototype represents a game changer, reaching over 10% (10.8) stabilized power conversion efficiency with unencapsulated long-term stability retaining 84% of its original efficiency over 1000 h under 70% RH and 25 °C.

Ruthenium(II) Polypyridyl Complexes as FRET Donors: Structure- and Sequence-Selective DNA-Binding and Anticancer Properties.

Ruthenium(II) polypyridyl complexes (RPCs) that emit from metal-to-ligand charge transfer (MLCT) states have been developed as DNA probes and are being examined as potential anticancer agents. Here, we report that MLCT-emissive RPCs that bind DNA undergo Förster resonance energy transfer (FRET) with Cy5.5-labeled DNA, forming mega-Stokes shift FRET pairs. Based on this discovery, we developed a simple and rapid FRET binding assay to examine DNA-binding interactions of RPCs with diverse photophysical properties, including non-"light switch" complexes [Ru(dppz)2(5,5'dmb)]2+ and [Ru(PIP)2(5,5'dmb)]2+ (dppz = dipyridophenazine, 5,5'dmb = 5,5'-dimethyl-2,2'-bipyridine, PIP = 2-phenyl-imidazo[4,5-f][1,10]phenanthroline). Binding affinities toward duplex, G-quadruplex, three-way junction, and mismatch DNA were determined, and derived FRET donor-acceptor proximities provide information on potential binding sites. Molecules characterized by this method demonstrate encouraging anticancer properties, including synergy with the PARP inhibitor Olaparib, and mechanistic studies indicate that [Ru(PIP)2(5,5'dmb)]2+ acts to block DNA replication fork progression.

Elucidating lipid conformations in the ripple phase: Machine learning reveals four lipid populations.

A new mixed radial-angular, three-particle correlation function method in combination with unsupervised machine learning was applied to examine the emergence of the ripple phase in dipalmitoylphosphatidylcholine (DPPC) lipid bilayers using data from atomistic molecular dynamics simulations of system sizes ranging from 128 to 4096 lipids. Based on the acyl tail conformations, the analysis revealed the presence of four distinct conformational populations of lipids in the ripple phases of the DPPC lipid bilayers. The expected gel-like (ordered; Lo) and fluid-like (disordered; Ld) lipids are found along with their splayed tail equivalents (Lo,s and Ld,s). These lipids differ, based on their gauche distribution and tail packing. The disordered (Ld) and disordered-splayed (Ld,s) lipids spatially cluster in the ripple in the groove side, that is, in an asymmetric manner across the bilayer leaflets. The ripple phase does not contain large numbers of Ld lipids; instead they only exist on the interface of the groove side of the undulation. The bulk of the groove side is a complex coexistence of Lo,Lo,s, and Ld,s lipids. The convex side of the undulation contains predominantly Lo lipids. Thus, the structure of the ripple phase is neither a simple coexistence of ordered and disordered lipids nor a coexistence of ordered interdigitating gel-like (Lo) and ordered-splayed (Lo,s) lipids, but instead a coexistence of an ordered phase and a complex mixed phase. Principal component analysis further confirmed the existence of the four lipid groups.

Prospective Study of Clinical Outcomes From a Breast Implant Assessment Service.

BACKGROUND: Breast augmentation remains the commonest cosmetic surgical procedure worldwide, in spite of recent regulatory action. OBJECTIVES: The aim of this study was to evaluate women with breast implants attending a breast implant assessment clinic and to capture clinical and implant data in women presenting to the service. METHODS: Patients were enrolled prospectively between January 2018 and December 2021. Clinical, implant, and practitioner data were recorded. Patients reported satisfaction on size, shape, and overall outcome as well as the presence or pain. Radiological evaluation, where indicated, was performed and data were included on these findings. RESULTS: A total of 603 patients were assessed. Their mean age was 42.7 years and mean age at implantation was 29.1 years. The most common complications were capsular contracture followed by pain, waterfall deformity, and double bubble, with rupture/contracture rates increasing after the 10-year mark. The risk of double bubble was significantly lower if patients were operated on by certified practitioners (odds ratio = 0.49, P = 0.011). There was almost universally poor awareness of the risks of breast implants in patients presenting for evaluation. CONCLUSIONS: This study has shown benefit in a breast implant assessment clinic to gather information on adverse events and patient-reported outcomes following breast implant surgery. Having appropriately trained and certified practitioners perform cosmetic augmentation significantly lowers the risk of implant malposition and deformity. Any adverse event occurring within 5 years of initial surgery should be flagged as a mandatory reportable clinical indicator and trigger further investigation.

Aerosol jet printing polymer dispersed liquid crystals on highly curved optical surfaces and edges.

We demonstrate a new technique for producing Polymer Dispersed Liquid Crystal (PDLC) devices utilising aerosol jet printing (AJP). PDLCs require two substrates to act as scaffold for the Indium Tin Oxide electrodes, which restricts the device geometries. Our approach precludes the requirement for the second substrate by printing the electrode directly onto the surface of the PDLC, which is also printed. The process has the potential to be precursory to the implementation of non-contact printing techniques for a variety of liquid crystal-based devices on non-planar substrates. We report the demonstration of direct deposition of PDLC films onto non-planar optical surfaces, including a functional device printed over the 90° edge of a prism. Scanning Electron Microscopy is used to inspect surface features of the polymer electrodes and the liquid crystal domains in the host polymer. The minimum relaxation time of the PDLC was measured at 1.3 ms with an 800 Hz, 90 V, peak-to-peak (Vpp) applied AC field. Cross-polarised transmission is reduced by up to a factor of 3.9. A transparent/scattering contrast ratio of 1.4 is reported between 0 and 140 V at 100 Hz.

Design, fabrication, and characterization of a tunable LED-based illuminator using refractive freeform arrays.

Dynamic illumination using tunable freeform arrays can enable spatial light distributions of variable size with high uniformity from non-uniform sources through relatively small opposing lateral shifts applied to the freeform components. We present the design, manufacturing, and characterization of a tunable LED-based illuminator using custom freeform Alvarez arrays with commercially available optics to shorten the manufacturing cycle. The optomechanical design and manufacturing of the Alvarez lens arrays and mounting parts are presented in detail. The optical performance of the system is evaluated and compared with simulation results using a custom camera-based test station. Experimental results demonstrate and confirm the dynamic illumination concept with good uniformity.

Grinding of silicon carbide for optical surface fabrication, Part 1: surface analysis.

This paper presents a study of the grinding of three different grades of silicon carbide (SiC) under the same conditions. Surface topography is analyzed using coherent scanning interferometry and scanning electron microscopy. The study provides a baseline understanding of the process mechanics and targets effective selection of process parameters for grinding SiC optics with near optical level surface roughness, thus reducing the need for post-polishing. Samples are raster and spiral ground on conventional precision machines with metal and copper-resin bonded wheels under rough, medium, and finish grinding conditions. Material microstructure and grinding conditions affect attainable surface roughness. Local surface roughness of less than 3 nm RMS was attained in both chemical vapor deposition (CVD) and chemical vapor composite (CVC) SiC. The tool footprint is suitable for sub-aperture machining of a large freeform optics possibly without the need for surface finish correction by post-polishing. Subsurface damage will be assessed in Part 2 of this paper series.