The effect of virtual reality-based therapy on fear of falling in multiple sclerosis: A systematic review and meta-analysis.

BACKGROUND: Virtual reality-based therapies is proposed in the rehabilitation of people with MS (pwMS). This systematic review aimed to summarize the effectiveness of virtual reality-based (VR) therapy on fear of falling (FoF) in pwMS. METHODS: PubMed (via MedLINE), the Cochrane Library, CINAHL, Scopus, Web of Science, Google Scholar, and ProQuest databases were systematically searched from inception until August 24, 2021. Randomized controlled trials (RCTs) examining the effect of VR therapy on FoF in pwMS as a primary or secondary outcome measure were selected. Potential articles were screened for eligibility and data were extracted by 3 independent reviewers. The methodological quality of the included studies was assessed using the PEDro scale and the risk of bias was independently assessed by three reviewers using the Cochrane Collaboration Risk of Bias tool. Raw (unstandardized) mean differences and standard deviations of the differences in the included studies were combined, and the overall mean effect size was calculated via a fixed-effects model for this study. RESULTS: Four RCTs with 140 participants were included in this review and meta-analysis. The studies included generally have a low or unclear risk of bias, and the quality of the methodology is low or high. The meta-analysis confirmed that VR therapy could reduce FoF in pwMS; VR therapy promoted improvement greater than conventional exercises/balance exercises or no intervention (MD, 2.98 95% CI 0.27 to 5.70; p = 0.0313). CONCLUSIONS: This study suggested that VR therapy could be an effective rehabilitative tool for reducing FoF in pwMS. However, due to the limited number of studies included, this result should be interpreted with caution.

The effect of TENS for pain relief in women with primary dysmenorrhea: A systematic review and meta-analysis.

OBJECTIVE: Primary dysmenorrhea (PD) is a chronic health condition that affects primarily young women and interferes with daily activities, causes loss of work productivity, and reduces quality of life. Transcutaneous electrical nerve stimulation (TENS) is a complementary and alternative therapy used to reduce pain related to PD. The purpose of this meta-analysis study was to evaluate the effectiveness of TENS in the treatment of pain in women with PD. METHODS: A search of the English literature in the Cochrane Library, MEDLINE (EBSCO), Physiotherapy Evidence Database (PEDro), CINAHL (EBSCO), PUBMED, OVID, Science Direct, Scopus, Academic Search Complete databases was conducted using combinations of the following search terms: 'primary dysmenorrhea', 'pain', 'transcutaneous electrical nerve stimulation', 'TENS', and 'electrical stimulation'. All content from database inception through April 2020 was included in the search. RESULTS: The initial search strategy based on date range and language yielded 571 relevant records and 4 of them were about both TENS and PD. A total of 260 patients were enrolled in the included studies. In all of the included studies, the comparison intervention consisted of sham TENS. The primary outcome of interest was pain intensity. Our analysis indicated that TENS was statistically more effective than sham TENS in reducing PD-related pain (SMD=1.384; 95% CI=0.505, 2.262; p = 0.002). CONCLUSION: TENS is a safe and well-tolerated electrophysical therapy that may be effective for relieving pain in PD.

Tuning electrical and interfacial thermal properties of bilayer MoS2via electrochemical intercalation.

Layered two-dimensional (2D) materials such as MoS2have attracted much attention for nano- and opto-electronics. Recently, intercalation (e.g. of ions, atoms, or molecules) has emerged as an effective technique to modulate material properties of such layered 2D films reversibly. We probe both the electrical and thermal properties of Li-intercalated bilayer MoS2nanosheets by combining electrical measurements and Raman spectroscopy. We demonstrate reversible modulation of carrier density over more than two orders of magnitude (from 0.8 × 1012to 1.5 × 1014cm-2), and we simultaneously obtain the thermal boundary conductance between the bilayer and its supporting SiO2substrate for an intercalated system for the first time. This thermal coupling can be reversibly modulated by nearly a factor of eight, from 14 ± 4.0 MW m-2K-1before intercalation to 1.8 ± 0.9 MW m-2K-1when the MoS2is fully lithiated. These results reveal electrochemical intercalation as a reversible tool to modulate and control both electrical and thermal properties of 2D layers.

Probing the Optical Properties and Strain-Tuning of Ultrathin Mo1- xW xTe2.

Ultrathin transition metal dichalcogenides (TMDCs) have recently been extensively investigated to understand their electronic and optical properties. Here we study ultrathin Mo0.91W0.09Te2, a semiconducting alloy of MoTe2, using Raman, photoluminescence (PL), and optical absorption spectroscopy. Mo0.91W0.09Te2 transitions from an indirect to a direct optical band gap in the limit of monolayer thickness, exhibiting an optical gap of 1.10 eV, very close to its MoTe2 counterpart. We apply tensile strain, for the first time, to monolayer MoTe2 and Mo0.91W0.09Te2 to tune the band structure of these materials; we observe that their optical band gaps decrease by 70 meV at 2.3% uniaxial strain. The spectral widths of the PL peaks decrease with increasing strain, which we attribute to weaker exciton-phonon intervalley scattering. Strained MoTe2 and Mo0.91W0.09Te2 extend the range of band gaps of TMDC monolayers further into the near-infrared, an important attribute for potential applications in optoelectronics.

Ultrafast Graphene Light Emitters.

Ultrafast electrically driven nanoscale light sources are critical components in nanophotonics. Compound semiconductor-based light sources for the nanophotonic platforms have been extensively investigated over the past decades. However, monolithic ultrafast light sources with a small footprint remain a challenge. Here, we demonstrate electrically driven ultrafast graphene light emitters that achieve light pulse generation with up to 10 GHz bandwidth across a broad spectral range from the visible to the near-infrared. The fast response results from ultrafast charge-carrier dynamics in graphene and weak electron-acoustic phonon-mediated coupling between the electronic and lattice degrees of freedom. We also find that encapsulating graphene with hexagonal boron nitride (hBN) layers strongly modifies the emission spectrum by changing the local optical density of states, thus providing up to 460% enhancement compared to the gray-body thermal radiation for a broad peak centered at 720 nm. Furthermore, the hBN encapsulation layers permit stable and bright visible thermal radiation with electronic temperatures up to 2000 K under ambient conditions as well as efficient ultrafast electronic cooling via near-field coupling to hybrid polaritonic modes under electrical excitation. These high-speed graphene light emitters provide a promising path for on-chip light sources for optical communications and other optoelectronic applications.

Dynamic Optical Tuning of Interlayer Interactions in the Transition Metal Dichalcogenides.

Modulation of weak interlayer interactions between quasi-two-dimensional atomic planes in the transition metal dichalcogenides (TMDCs) provides avenues for tuning their functional properties. Here we show that above-gap optical excitation in the TMDCs leads to an unexpected large-amplitude, ultrafast compressive force between the two-dimensional layers, as probed by in situ measurements of the atomic layer spacing at femtosecond time resolution. We show that this compressive response arises from a dynamic modulation of the interlayer van der Waals interaction and that this represents the dominant light-induced stress at low excitation densities. A simple analytic model predicts the magnitude and carrier density dependence of the measured strains. This work establishes a new method for dynamic, nonequilibrium tuning of correlation-driven dispersive interactions and of the optomechanical functionality of TMDC quasi-two-dimensional materials.

Temperature-Dependent Thermal Boundary Conductance of Monolayer MoS2 by Raman Thermometry.

The electrical and thermal behavior of nanoscale devices based on two-dimensional (2D) materials is often limited by their contacts and interfaces. Here we report the temperature-dependent thermal boundary conductance (TBC) of monolayer MoS2 with AlN and SiO2, using Raman thermometry with laser-induced heating. The temperature-dependent optical absorption of the 2D material is crucial in such experiments, which we characterize here for the first time above room temperature. We obtain TBC ∼ 15 MW m-2 K-1 near room temperature, increasing as ∼ T0.65 in the range 300-600 K. The similar TBC of MoS2 with the two substrates indicates that MoS2 is the "softer" material with weaker phonon irradiance, and the relatively low TBC signifies that such interfaces present a key bottleneck in energy dissipation from 2D devices. Our approach is needed to correctly perform Raman thermometry of 2D materials, and our findings are key for understanding energy coupling at the nanoscale.

In-Plane Anisotropy in Mono- and Few-Layer ReS2 Probed by Raman Spectroscopy and Scanning Transmission Electron Microscopy.

Rhenium disulfide (ReS2) is a semiconducting layered transition metal dichalcogenide that exhibits a stable distorted 1T phase. The reduced symmetry of this system leads to in-plane anisotropy in various material properties. Here, we demonstrate the strong anisotropy in the Raman scattering response for linearly polarized excitation. Polarized Raman scattering is shown to permit a determination of the crystallographic orientation of ReS2 through comparison with direct structural analysis by scanning transmission electron microscopy (STEM). Analysis of the frequency difference of appropriate Raman modes is also shown to provide a means of precisely determining layer thickness up to four layers.

Optical properties and band gap of single- and few-layer MoTe2 crystals.

Single- and few-layer crystals of exfoliated MoTe2 have been characterized spectroscopically by photoluminescence, Raman scattering, and optical absorption measurements. We find that MoTe2 in the monolayer limit displays strong photoluminescence. On the basis of complementary optical absorption results, we conclude that monolayer MoTe2 is a direct-gap semiconductor with an optical band gap of 1.10 eV. This new monolayer material extends the spectral range of atomically thin direct-gap materials from the visible to the near-infrared.