Optical Fourier surfaces.

Gratings1 and holograms2 use patterned surfaces to tailor optical signals by diffraction. Despite their long history, variants with remarkable functionalities continue to be developed3,4. Further advances could exploit Fourier optics5, which specifies the surface pattern that generates a desired diffracted output through its Fourier transform. To shape the optical wavefront, the ideal surface profile should contain a precise sum of sinusoidal waves, each with a well defined amplitude, spatial frequency and phase. However, because fabrication techniques typically yield profiles with at most a few depth levels, complex 'wavy' surfaces cannot be obtained, limiting the straightforward mathematical design and implementation of sophisticated diffractive optics. Here we present a simple yet powerful approach to eliminate this design-fabrication mismatch by demonstrating optical surfaces that contain an arbitrary number of specified sinusoids. We combine thermal scanning-probe lithography6-8 and templating9 to create periodic and aperiodic surface patterns with continuous depth control and sub-wavelength spatial resolution. Multicomponent linear gratings allow precise manipulation of electromagnetic signals through Fourier-spectrum engineering10. Consequently, we overcome a previous limitation in photonics by creating an ultrathin grating that simultaneously couples red, green and blue light at the same angle of incidence. More broadly, we analytically design and accurately replicate intricate two-dimensional moiré patterns11,12, quasicrystals13,14 and holograms15,16, demonstrating a variety of previously unattainable diffractive surfaces. This approach may find application in optical devices (biosensors17, lasers18,19, metasurfaces4 and modulators20) and emerging areas in photonics (topological structures21, transformation optics22 and valleytronics23).

Photonic Artifacts in Ratiometric Luminescence Nanothermometry.

Ongoing developments in science and technology require temperature measurements at increasingly higher spatial resolutions. Nanocrystals with temperature-sensitive luminescence are a popular thermometer for these applications offering high precision and remote read-out. Here, we demonstrate that ratiometric luminescence thermometry experiments may suffer from systematic errors in nanostructured environments. We place lanthanide-based luminescent nanothermometers at controlled distances of up to 600 nm from a Au surface. Although this geometry supports no absorption or scattering resonances, distortion of the emission spectra of the thermometers due to the modified density of optical states results in temperature read-out errors of up to 250 K. Our simple analytical model explains the effects of thermometer emission frequencies, experimental equipment, and sample properties on the magnitude of the errors. We discuss the relevance of our findings in several experimental scenarios. Such errors do not always occur, but they are expected in measurements near reflecting interfaces or scattering objects.

Size-Dependent Optical Properties of InP Colloidal Quantum Dots.

Indium phosphide colloidal quantum dots (CQDs) are the main alternative for toxic and restricted Cd based CQDs for lighting and display applications. Here we systematically report on the size-dependent optical absorption, ensemble, and single particle photoluminescence (PL) and biexciton lifetimes of core-only InP CQDs. This systematic study is enabled by improvements in the synthesis of InP CQDs to yield a broad size series of monodisperse core-only InP CQDs with narrow absorption and PL line width and significant PL quantum yield.

Biexciton Binding Energy and Line width of Single Quantum Dots at Room Temperature.

Broadening of multiexciton emission from colloidal quantum dots (QDs) at room temperature is important for their use in high-power applications, but an in-depth characterization has not been possible until now. We present and apply a novel spectroscopic method to quantify the biexciton line width and biexciton binding energy of single CdSe/CdS/ZnS colloidal QDs at room temperature. In our method, which we term "cascade spectroscopy", we select emission events from the biexciton cascade and reconstruct their spectrum. The biexciton has an average emission line width of 86 meV on the single-QD scale, similar to that of the exciton. Variations in the biexciton repulsion (Eb = 4.0 ± 3.1 meV; mean ± standard deviation of 15 QDs) are correlated with but are more narrowly distributed than variations in the exciton energy (10.0 meV standard deviation). Using a simple quantum-mechanical model, we conclude that inhomogeneous broadening in our sample is primarily due to variations in the CdS shell thickness.

Refractory juvenile myoclonic epilepsy: a meta-analysis of prevalence and risk factors.

BACKGROUND AND PURPOSE: Juvenile myoclonic epilepsy (JME) is a common epilepsy syndrome for which treatment response is generally assumed to be good. We aimed to determine the prevalence and prognostic risk factors for refractoriness of JME. METHODS: We systematically searched PubMed and EMBASE and included 43 eligible studies, reporting seizure outcome after antiepileptic drug (AED) treatment in JME cohorts. We defined refractory JME as persistence of any seizure despite AED treatment and performed a random-effects meta-analysis to assess the prevalence of refractory JME and of seizure recurrence after AED withdrawal in individuals with well-controlled seizures. Studies reporting potential prognostic risk factors in relation to seizure outcome were included for subsequent meta-analysis of risk factors for refractoriness. RESULTS: Overall, 35% (95% confidence interval, 29-41%) of individuals (n = 3311) were refractory. There was marked heterogeneity between studies. Seizures recurred in 78% (95% confidence interval, 52-94%) of individuals who attempted to withdraw from treatment after a period of seizure freedom (n = 246). Seizure outcome by publication year suggested that prognosis did not improve over time. Meta-analysis suggested six variables as prognostic factors for refractoriness, i.e. having three seizure types, absence seizures, psychiatric comorbidities, earlier age at seizure onset, history of childhood absence epilepsy and praxis-induced seizures. CONCLUSION: One-third of people with JME were refractory, which is a higher prevalence than expected. Risk factors were identified and can be used to guide treatment and counselling of people with JME.

Comparing two classification schemes for seizures and epilepsy in rural China.

BACKGROUND AND PURPOSE: The International League against Epilepsy (ILAE) updated the classifications of seizures and epilepsies in 2017. The 2017 classifications were compared with the 1980s classifications in rural China. METHODS: People with epilepsy receiving treatment under the National Epilepsy Control Programme were recruited from rural areas in China. Their seizures and epileptic syndrome were classified using the 1980s ILAE classification system and then re-classified according to the 2017 system. Differences in seizure, epilepsy and aetiology classifications were identified. RESULTS: A total of 597 individuals (58% males, aged 6-78 years) were included. Amongst them 535 (90%) had a single seizure type, 57 (9.55%) had two types and five (0.84%) had three. There was complete agreement between the 1981 and 2017 classifications for the 525 individuals with focal seizures. Seizures originally classified as generalized in 10 of 65 individuals were re-classified as unknown in the 2017 classification. Compared to the 1980s classifications, the proportion of individuals with unknown seizures and unknown epilepsy increased from 1.2% (7/597) to 2.8% (17/597, P = 0.002), and unknown aetiology increased from 32% (189/597: 182 cryptogenic and seven unclassified) to 39% (230/597; P < 0.001) in the 2017 classifications. CONCLUSIONS: The 1980s and 2017 classifications had 100% agreement in classifying focal seizures and epilepsy in rural China. A small but significant proportion of generalized seizures and epilepsy and aetiologies classified in the old classifications were re-classified to unknown in the new classifications. These results highlight the need for improvement in clinical evaluation of people with epilepsy in resource-poor settings.

Decreasing the risk of sudden unexpected death in epilepsy: structured communication of risk factors for premature mortality in people with epilepsy.

BACKGROUND AND PURPOSE: Good practice guidelines highlight the importance of making people with epilepsy aware of the risk of premature mortality in epilepsy particularly due to sudden unexpected death in epilepsy (SUDEP). The SUDEP and Seizure Safety Checklist ('Checklist') is a structured risk communication tool used in UK clinics. It is not known if sharing structured information on risk factors allows individuals to reduce SUDEP and premature mortality risks. The aim of this study was to ascertain if the introduction of the Checklist in epilepsy clinics led to individual risk reduction. METHODS: The Checklist was administered to 130 consecutive people with epilepsy attending a specialized epilepsy neurology clinic and 129 attending an epilepsy intellectual disability (ID) clinic within a 4-month period. At baseline, no attendees at the neurology clinic had received formal risk advice, whereas all those attending the ID clinic had received formal risk advice on multiple occasions for 6 years. The Checklist was readministered 1 year later to each group and scores were compared with baseline and between groups. RESULTS: Of 12 risk factors considered, there was an overall reduction in mean risk score for the general (P = 0.0049) but not for the ID (P = 0.322) population. Subanalysis of the 25% of people at most risk in both populations showed that both sets had a significant reduction in risk scores (P < 0.001). CONCLUSION: Structured discussion results in behavioural change that reduces individual risk factors. This impact seems to be higher in those who are at current higher risk. It is important that clinicians share risk information with individuals as a matter of public health and health promotion.

Epilepsy as a systemic condition: Link with somatic comorbidities.

BACKGROUND: People with epilepsy have more concomitant medical conditions than the general population; these comorbidities play an important role in premature mortality. We sought to generate explanatory hypotheses about the co-occurrence of somatic comorbidities and epilepsy, avoiding causal and treatment-resultant biases. METHODS: We collected clinical, demographic and somatic comorbidity data for 2016 consecutive adults with epilepsy undergoing assessment at a tertiary centre and in 1278 people with epilepsy in the community. Underlying causes of epilepsy were not classed as comorbidities. RESULTS: Somatic comorbidities were more frequent in the referral centre (49%) where people more frequently had active epilepsy than in the community (36%). Consistent risk factors for comorbidities were found in both cohorts. Using multivariable ordinal regression adjusted for age, longer epilepsy duration and an underlying brain lesion were independently associated with a smaller burden of somatic conditions. The treatment burden, measured by the number of drugs to which people were exposed, was not an independent predictor. Shorter epilepsy duration was a predictor for conditions that conceivably harbour significant mortality risks. CONCLUSIONS: Somatic comorbidities do not occur randomly in relation to epilepsy; having more severe epilepsy seems to be a risk factor. Independently from age, the early period after epilepsy onset appears to be at particular risk, although it is not clear whether this relates to an early mortality or to a later decrease in the burden of comorbidities. These results suggest that, for some people, epilepsy should be considered a systemic condition not limited to the CNS.

Electro-clinical criteria and surgical outcome: Is there a difference between mesial and lesional temporal lobe epilepsy?

OBJECTIVES: Mesial temporal lobe epilepsy syndrome (MTLE) with specific electrophysiological and clinical characteristics and hippocampal sclerosis (HS) on MRI is considered the prototype of a syndrome with good surgical prognosis. Ictal onset zones in MTLE have been found to extend outside the hippocampus and neocortical seizures often involve mesial structures. It can, thus, be questioned whether MTLE with HS is different from lesional temporal epilepsies with respect to electro-clinical characteristics and surgical prognosis. We assessed whether MTLE with HS is distinguishable from lesional TLE and which criteria determine surgical outcome. METHODS: People in a retrospective cohort of 389 individuals with MRI abnormalities who underwent temporal lobectomy, were divided into "HS only" or "lesional" TLEs. Twenty-six presented with dual pathology and were excluded from further analysis. We compared surgical outcome and electro-clinical characteristics. RESULTS: Over half (61%) had "HS only." Four electro-clinical characteristics (age at epilepsy onset, febrile seizures, memory dysfunction and contralateral dystonic posturing) distinguished "HS only" from "lesional" TLE, but there was considerable overlap. Seizure freedom 2 years after surgery (Engel class 1) was similar: 67% ("HS only") vs 69% ("lesional" TLE). Neither presence of HS nor electro-clinical criteria was associated with surgical outcome. CONCLUSIONS: Despite small differences in electrophysiological and clinical characteristics between MTLE with HS and lesional TLE, surgical outcomes are similar, indicating that aetiology seems irrelevant in the referral for temporal surgery.

Oleic Acid-Induced Atomic Alignment of ZnS Polyhedral Nanocrystals.

Ordered two-dimensional (2D) superstructures of colloidal nanocrystals (NCs) can be tailored by the size, shape, composition, and surface chemistry of the NC building blocks, which can give directionality to the resulting superstructure geometry. The exact formation mechanism of 2D NC superstructures is however not yet fully understood. Here, we show that oleic acid (OA) ligands induce atomic alignment of wurtzite ZnS bifrustum-shaped NCs. We find that in the presence of OA ligands the {002} facets of the ZnS bifrustums preferentially adhere to the liquid-air interface. Furthermore, OA ligands induce inter-NC interactions that also orient the NCs in the plane of the liquid-air interface, resulting in atomically aligned 2D superstructures. We follow the self-assembly process in real-time with in situ grazing incidence small-angle X-ray scattering and find that the NCs form a hexagonal superstructure at early stages after which they come closer over time, resulting in a close-packed NC superstructure. Our results demonstrate the profound influence that surface ligands have on the directionality of 2D NC superstructures and highlight the importance of detailed in situ studies in order to understand the self-assembly of NCs into 2D superstructures.

Long-term prognosis of epilepsy, prognostic patterns and drug resistance: a population-based study.

BACKGROUND AND PURPOSE: Seizures in most people with epilepsy remit but prognostic markers are poorly understood. There is also little information on the long-term outcome of people who fail to achieve seizure control despite the use of two antiepileptic drugs (drug resistance). METHODS: People with a validated diagnosis of epilepsy in whom two antiepileptic drugs had failed were identified from primary care records. All were registered with one of 123 family physicians in an area of northern Italy. Remission (uninterrupted seizure freedom lasting 2 years or longer) and prognostic patterns (early remission, late remission, remission followed by relapse, no remission) were determined. RESULTS: In all, 747 individuals (381 men), aged 11 months to 94 years, were followed for 11 045.5 person-years. 428 (59%) were seizure-free. The probability of achieving 2-year remission was 18% at treatment start, 34% at 2 years, 45% at 5, 52% at 10 and 67% at 20 years (terminal remission, 60%). Epilepsy syndrome and drug resistance were the only independent predictors of 2- and 5-year remission. Early remission was seen in 101 people (19%), late remission in 175 (33%), remission followed by relapse in 85 (16%) and no remission in 166 (32%). Treatment response was the only variable associated with differing prognostic patterns. CONCLUSION: The long-term prognosis of epilepsy is favourable in most cases. Early seizure remission is not invariably followed by terminal remission and seizure outcome varies according to well-defined patterns. Prolonged seizure remission and prognostic patterns can be predicted by broad syndromic categories and the failure of two antiepileptic drugs.

Epidemiology, pathophysiology and putative genetic basis of carbamazepine- and oxcarbazepine-induced hyponatremia.

The use of carbamazepine (CBZ) and oxcarbazepine (OXC) as first-line antiepileptic drugs in the treatment of focal epilepsy is limited by hyponatremia, a known adverse effect. Hyponatremia occurs in up to half of people taking CBZ or OXC and, although often assumed to be asymptomatic, it can lead to symptoms ranging from unsteadiness and mild confusion to seizures and coma. Hyponatremia is probably due to the antidiuretic properties of CBZ and OXC that are, at least partly, explained by stimulation of the vasopressin 2 receptor/aquaporin 2 pathway. No known genetic risk variants for CBZ- and OXC-induced hyponatremia exist, but likely candidate genes are part of the vasopressin water reabsorption pathway.

Managing anti-epileptic drug treatment in adult patients with intellectual disability: a serious conundrum.

BACKGROUND AND PURPOSE: About a quarter of people with epilepsy have intellectual disability (ID). This group has communication issues, premature mortality, more treatment resistance, difficulties in making informed choices and greater risks of physical and mental health comorbidities. There is no specific prescribing guidance for this large and vulnerable group. The literature on prescribing for epilepsy in this group was reviewed, in particular examining how antiepileptic drugs (AEDs) work regarding their side effect profiles, effects on specific epilepsy syndromes associated with ID and their individual strengths and weaknesses based on the nature and degree of ID. METHOD: This is a narrative review for which a comprehensive search was conducted to identify evidence for prescribing commonly used AEDs to people with ID including genetic syndromes specifically associated with epilepsy. RESULTS: A detailed analysis of the results has highlighted the urgent requirement for suitable and reliable evidence in AED prescribing amongst adults with epilepsy and ID as no studies taking account of the response to AEDs of the ID populations based on the WHO Diagnostic and Statistical Manual of Mental Disorders criteria of clinical severity of ID were identified. CONCLUSION: There is a significant shortfall in suitably powered studies to provide sufficient evidence for safe prescribing of AEDs to people with ID.

Anti-epileptic drug changes and quality of life in the community.

OBJECTIVE: Changes in anti-epileptic drug (AED) regimens may indicate unsatisfactory treatment results such as insufficient seizure control or adverse effects. This inference underlies epilepsy management and research, yet current studies often do not account for AED changes. We assessed AED change patterns and their association with quality of life (QoL), as main outcome measure, in a community-based setting. METHODS: We assessed a cohort of 248 people with epilepsy identified from community pharmacy records from whom we retrieved AED dispensing history. We assessed all changes in AED use during the 2 years prior to the index date and current QoL using the validated Dutch QOLIE-31 questionnaire. RESULTS: Thirty-one per cent had at least one AED change during the study period, either in drug type or dose. People who changed showed significantly lower QoL (QOLIE score 73 vs 79), especially those who intensified their treatment. Each additional change was associated with a further reduction of 4.9 points in QoL score. CONCLUSIONS: AED changes are common practice, even in people with long-standing epilepsy. Frequent changes, as objective measure of epilepsy severity, are associated with a progressively lower QoL. Changes, even in dose, should be monitored in daily clinical practice and used as a red flag that may require adjustments in epilepsy management. This may include earlier referral to a specialized centre for a more thorough evaluation or counselling. AED changes can also be used as an outcome marker in epilepsy research as a proxy of QoL for better translation of drug-efficacy results to general practice.

Increased prevalence of ECG markers for sudden cardiac arrest in refractory epilepsy.

BACKGROUND AND AIM: People with epilepsy are at increased risk of sudden cardiac arrest (SCA) due to ECG-confirmed ventricular tachycardia/fibrillation, as seen in a community-based study. We aimed to determine whether ECG-risk markers of SCA are more prevalent in people with epilepsy. METHODS: In a cross-sectional, retrospective study, we analysed the ECG recordings of 185 people with refractory epilepsy and 178 controls without epilepsy. Data on epilepsy characteristics, cardiac comorbidity, and drug use were collected, and general ECG variables (heart rate (HR), PQ and QRS intervals) assessed. We analysed ECGs for three markers of SCA risk: severe QTc prolongation (male >450 ms, female >470 ms), Brugada ECG pattern, and early repolarisation pattern (ERP). Multivariate regression models were used to analyse differences between groups, and to identify associated clinical and epilepsy-related characteristics. RESULTS: People with epilepsy had higher HR (71 vs 62 bpm, p<0.001) and a longer PQ interval (162.8 vs 152.6 ms, p=0.001). Severe QTc prolongation and ERP were more prevalent in people with epilepsy (QTc prolongation: 5% vs 0%; p=0.002; ERP: 34% vs 13%, p<0.001), while the Brugada ECG pattern was equally frequent in both groups (2% vs 1%, p>0.999). After adjustment for covariates, epilepsy remained associated with ERP (ORadj 2.4, 95% CI 1.1 to 5.5) and severe QTc prolongation (ORadj 9.9, 95% CI 1.1 to 1317.7). CONCLUSIONS: ERP and severe QTc prolongation appear to be more prevalent in people with refractory epilepsy. Future studies must determine whether this contributes to increased SCA risk in people with epilepsy.

The comorbid relationship between migraine and epilepsy: a systematic review and meta-analysis.

A number of studies have suggested a pathophysiologic link between migraine and epilepsy. Our aim was to examine the relative lifetime prevalence of migraine in people with epilepsy (PWE) as well that of epilepsy in migraineurs. We carried out a systematic review, searching five electronic databases, specified bibliographies and conference abstracts in order to identify population-based studies that measured the lifetime co-prevalence of migraine and epilepsy. Two reviewers independently screened all titles and abstracts, carried out a risk of bias assessment and extracted the data. Meta-analyses were carried out using random effects models. Of the 3640 abstracts and titles screened, we identified 10 eligible studies encompassing a total of 1,548,967 subjects. Few of the studies used validated case ascertainment tools and there were inconsistent attempts to control for confounding. There was an overall 52% increase in the prevalence of migraine among PWE versus those without epilepsy [PR: 1.52 (95% CI: 1.29, 1.79)]. There was an overall 79% increase in the prevalence of epilepsy among migraineurs versus those without migraine [PR: 1.79 (95% CI: 1.43, 2.25)]. Subgroup analyses revealed that the method of ascertaining the epilepsy or migraine status of subjects was an important source of inter-study heterogeneity. Additional high quality primary studies are required, ones that use validated and accurate methods of case ascertainment as well as control for potential confounders.

Serum brain-derived neurotrophic factor levels in epilepsy.

BACKGROUND AND PURPOSE: To clarify the utility of serum brain-derived neurotrophic factor (BDNF) as a biomarker for epilepsy diagnosis and severity. METHODS: Serum BDNF levels in 135 consecutive people with epilepsy meeting our criteria were assessed. Controls were 34 healthy individuals who over 12 months or longer had no complaints or signs of a neurological disorder. Serum BDNF concentrations were measured using Luminex technology. RESULTS: Gender, but not age, was found to be a significant factor related to serum BDNF levels in controls and people with epilepsy. Serum BDNF levels in people with epilepsy (mean 8798.5, SE 321.5 pg/ml) were not different from those of controls (mean 8919.5, SE 709.0 pg/ml). A multiple linear regression analysis, however, suggests that seizure frequency (P < 0.001) and epilepsy duration (P = 0.025) negatively correlate with serum BDNF levels independently of other factors. When BDNF cut-off values of 6260 pg/ml were used, the sensitivity for distinguishing people with daily or more frequent seizures from those with fewer seizures was 80% and specificity was 90%. CONCLUSIONS: It seems that the concentration of BDNF in serum is associated with disease severity in people with epilepsy and may be a helpful marker for severity.

Effect of oral contraceptives on lamotrigine levels depends on comedication.

OBJECTIVES: To evaluate prospectively the influence of cyclic oral contraceptive (OC) use on lamotrigine (LTG) serum levels when used in combination therapy. METHODS: Women with epilepsy using LTG in combination with valproate (VPA; n=7), carbamazepine (CBZ; n=3) or oxcarbazepine (OXC; n=1) were evaluated during two periods of 28 days cyclic OC use, monitoring antiepileptic drug (AED) levels every other day with the dried blood spot sampling method. Results were compared with women on LTG monotherapy and OCs (n=12). Pharmacokinetic analysis was performed using NONMEM software. RESULTS: Mean study population value of LTG clearance estimated by the final model was 3.17 l/h. Introduction of covariates for comedication (VPA, CBZ, OXC and OC) significantly reduced the between-subject variability. A significant influence of OC comedication on LTG clearance was seen in both LTG monotherapy (clearance with OC 4.02±0.38 l/h, OC-free week 3.03±0.39 l/h) and in LTG-CBZ combination (clearance with OC 4.95±0.15 l/h, OC-free week 4.15±0.26 l/h). No influence of OC was found in LTG-VPA combination (clearance with OC 0.99±0.16 l/h, OC-free week 0.90±0.15 l/h). CONCLUSIONS: Adding OCs to LTG monotherapy or the combination LTG-CBZ significantly increased the LTG clearance and thus reduced LTG serum levels. In the combination LTG-CBZ, OCs had a non-significant effect on CBZ clearance. No significant influence of cyclic OC use on LTG or VPA clearance was found when these AEDs were used in combination.

Fluctuations in the Photoluminescence Excitation Spectra of Individual Semiconductor Nanocrystals.

Most single quantum emitters display non-steady emission properties. Models that explain this effect have primarily relied on photoluminescence measurements that reveal variations in intensity, wavelength, and excited-state lifetime. While photoluminescence excitation spectroscopy could provide complementary information, existing experimental methods cannot collect spectra before individual emitters change in intensity (blink) or wavelength (spectrally diffuse). Here, we present an experimental approach that circumvents such issues, allowing the collection of excitation spectra from individual emitters. Using rapid modulation of the excitation wavelength, we collect and classify excitation spectra from individual CdSe/CdS/ZnS core/shell/shell quantum dots. The spectra, along with simultaneous time-correlated single-photon counting, reveal two separate emission-reduction mechanisms caused by charging and trapping, respectively. During bright emission periods, we also observe a correlation between emission red-shifts and the increased oscillator strength of higher excited states. Quantum-mechanical modeling indicates that diffusion of charges in the vicinity of an emitter polarizes the exciton and transfers the oscillator strength to higher-energy transitions.