Update to the Hong Kong Epilepsy Guideline: evidence-based recommendations for clinical management of women with epilepsy throughout the reproductive cycle.

Since the publication of the Hong Kong Epilepsy Guideline in 2009, there has been significant progress in antiepileptic drug development. New AEDs have emerged, and data about their uses have been published. Women require special attention in epilepsy care. Drug teratogenicity, pregnancy, breastfeeding, contraception, reproduction technology, menopause, and catamenial epilepsy are major topics. Antiepileptic drugs should be chosen individually for patients who are pregnant or may become pregnant with consideration of their teratogenicity and seizure control properties. Folate is commonly prescribed for women of childbearing age who are taking antiepileptic drugs. Spontaneous vaginal delivery and breastfeeding are not contra-indicated in most cases but need to be considered individually based on the patient's medical condition and wishes. Serum drug level monitoring of certain antiepileptic drugs during pregnancy and puerperium can guide dosage adjustment. For catamenial epilepsy, intermittent benzodiazepines such as clobazam during the susceptible phase of the menstrual cycle could be a treatment option.

Observation of Exciton Redshift-Blueshift Crossover in Monolayer WS2.

We report a rare atom-like interaction between excitons in monolayer WS2, measured using ultrafast absorption spectroscopy. At increasing excitation density, the exciton resonance energy exhibits a pronounced redshift followed by an anomalous blueshift. Using both material-realistic computation and phenomenological modeling, we attribute this observation to plasma effects and an attraction-repulsion crossover of the exciton-exciton interaction that mimics the Lennard-Jones potential between atoms. Our experiment demonstrates a strong analogy between excitons and atoms with respect to interparticle interaction, which holds promise to pursue the predicted liquid and crystalline phases of excitons in two-dimensional materials.

Coupling and Stacking Order of ReS2 Atomic Layers Revealed by Ultralow-Frequency Raman Spectroscopy.

We investigate the ultralow-frequency Raman response of atomically thin ReS2, a special type of two-dimensional (2D) semiconductors with unique distorted 1T structure. Bilayer and few-layer ReS2 exhibit rich Raman spectra at frequencies below 50 cm(-1), where a panoply of interlayer shear and breathing modes are observed. The emergence of these interlayer phonon modes indicate that the ReS2 layers are coupled and orderly stacked. Whereas the interlayer breathing modes behave similarly to those in other 2D layered crystals, the shear modes exhibit distinctive behavior due to the in-plane lattice distortion. In particular, the two shear modes in bilayer ReS2 are nondegenerate and clearly resolved in the Raman spectrum, in contrast to the doubly degenerate shear modes in other 2D materials. By carrying out comprehensive first-principles calculations, we can account for the frequency and Raman intensity of the interlayer modes and determine the stacking order in bilayer ReS2.

Trion-induced negative photoconductivity in monolayer MoS2.

Optical excitation typically enhances electrical conduction and low-frequency radiation absorption in semiconductors. We, however, observe a pronounced transient decrease of conductivity in doped monolayer molybdenum disulfide (MoS(2)), a two-dimensional (2D) semiconductor, using ultrafast optical-pump terahertz-probe spectroscopy. In particular, the conductivity is reduced to only 30% of its equilibrium value at high pump fluence. This anomalous phenomenon arises from the strong many-body interactions in the 2D system, where photoexcited electron-hole pairs join the doping-induced charges to form trions, bound states of two electrons and one hole. The resultant increase of the carrier effective mass substantially diminishes the conductivity.

Semiconducting-to-metallic photoconductivity crossover and temperature-dependent Drude weight in graphene.

We investigate the transient photoconductivity of graphene at various gate-tuned carrier densities by optical-pump terahertz-probe spectroscopy. We demonstrate that graphene exhibits semiconducting positive photoconductivity near zero carrier density, which crosses over to metallic negative photoconductivity at high carrier density. These observations can be accounted for by the interplay between photoinduced changes of both the Drude weight and carrier scattering rate. Our findings provide a complete picture to explain the opposite photoconductivity behavior reported in (undoped) graphene grown epitaxially and (doped) graphene grown by chemical vapor deposition. Notably, we observe nonmonotonic fluence dependence of the photoconductivity at low carrier density. This behavior reveals the nonmonotonic temperature dependence of the Drude weight in graphene, a unique property of two-dimensional massless Dirac fermions.

Spin-induced optical conductivity in the spin-liquid candidate herbertsmithite.

We report a direct measurement of the low-frequency optical conductivity of large-area single-crystal herbertsmithite, a promising spin-liquid candidate material, by means of terahertz time-domain spectroscopy. In the spectral range below 1.4 THz, we observe a contribution to the real part of the in-plane conductivity σ(ab)(ω) from the spin degree of freedom. This spin-induced conductivity exhibits a power-law dependence on frequency σ(ab)(ω) ~ ω(ß) with ß ≈ 1.4. Our observation is consistent with the theoretically predicted low-frequency conductivity arising from an emergent gauge field of a gapless U(1) Dirac spin liquid.

Magnetoencephalography and its role in evaluation for epilepsy surgery.

Magnetoencephalography is a newly developed technology used for diagnostic and brain mapping imaging during the presurgical evaluation of patients with medically intractable epilepsy. It provides comprehensive localisation of an epileptogenic focus using simultaneous recordings from the entire brain surface. Magnetoencephalography and electroencephalography are considered complementary and confirmatory to one another. We present a patient with magnetic resonance imaging-negative, non-lesional, neocortical epilepsy. Magnetoencephalography was used for re-evaluation of the epileptogenic zone and this enabled subsequent surgical removal of the epileptic focus. The role of magnetoencephalography in epilepsy surgery is discussed in this report.

Spatial and temporal vision in patients treated for bilateral congenital cataracts.

Using the method of limits, we measured spatial and temporal vision in 13 children who had been deprived of patterned visual input during infancy until they were treated for dense central cataracts in both eyes. Spatial vision was assessed with vertical sine-wave gratings, and temporal vision was assessed with an unpatterned luminance field sinusoidally modulated over time. Under these testing conditions, spatial contrast sensitivity at low and medium spatial frequencies (0.33-2 c deg-1) was within normal limits, but sensitivity at higher spatial frequencies and grating acuity were reduced on average by 1.3 and 0.5 log units, respectively. Temporal vision was affected less severely, with losses in sensitivity only for low temporal frequencies (5 and 10 Hz), which averaged 0.4 log units. Thus, spatial and temporal vision are likely mediated by different neural mechanisms, that are differentially affected by deprivation.