An ultrafast symmetry switch in a Weyl semimetal.

Topological quantum materials exhibit fascinating properties1-3, with important applications for dissipationless electronics and fault-tolerant quantum computers4,5. Manipulating the topological invariants in these materials would allow the development of topological switching applications analogous to switching of transistors6. Lattice strain provides the most natural means of tuning these topological invariants because it directly modifies the electron-ion interactions and potentially alters the underlying crystalline symmetry on which the topological properties depend7-9. However, conventional means of applying strain through heteroepitaxial lattice mismatch10 and dislocations11 are not extendable to controllable time-varying protocols, which are required in transistors. Integration into a functional device requires the ability to go beyond the robust, topologically protected properties of materials and to manipulate the topology at high speeds. Here we use crystallographic measurements by relativistic electron diffraction to demonstrate that terahertz light pulses can be used to induce terahertz-frequency interlayer shear strain with large strain amplitude in the Weyl semimetal WTe2, leading to a topologically distinct metastable phase. Separate nonlinear optical measurements indicate that this transition is associated with a symmetry change to a centrosymmetric, topologically trivial phase. We further show that such shear strain provides an ultrafast, energy-efficient way of inducing robust, well separated Weyl points or of annihilating all Weyl points of opposite chirality. This work demonstrates possibilities for ultrafast manipulation of the topological properties of solids and for the development of a topological switch operating at terahertz frequencies.

Dietary Taurine Supplementation in School Meals Has Positive Effect on School Attitude Assessment in Korean High School Students.

This study was conducted to evaluate the effect of supplementation with taurine-rich foods on school attitude assessment (SAA) in high school students. A total of 134 subjects were divided into a taurine-rich food supplemented (TS) group (68 subjects) and control group (66 subjects). For the TS group, school dinners supplemented with taurine-rich foods were provided for 5 days and average dietary amount of taurine supplementation was 466.2 mg/school dinner. Control group ate dinner at home or at restaurant ad libitum. The school attitude assessment survey-revised and 24-h recall method were used for SAA and dietary assessment, respectively. There were no significant differences in scores of dietary attitudes between the TS and control groups by gender. Average dietary taurine intake of the TS group (649.8 mg/day in males, 634.5 mg/day in females) was significantly higher compared to the control group (392.4 mg/day in males, 334.4 mg/day in females) (p < 0.01 in males and p < 0.001 in females, respectively). Total SAA scores in the TS group were significantly higher compared to the control group (p < 0.01) for attitudes toward teachers, goal valuation, and motivation/self-regulation (p < 0.01). Dietary taurine intake was showed positive correlations with scores for academic self-perception (p < 0.05), attitudes towards teachers (p < 0.001), goal valuation (p < 0.01), motivation/self-regulation (p < 0.05), and total scores (p < 0.01). According to the results, dietary taurine supplementation in school meals for 5 days had a positive effect on SAA in high school students. Therefore, dietary taurine supplementation in school and home meals may be necessary for improving SAA of high school students.

Patterning droplets with durotaxis.

Numerous cell types have shown a remarkable ability to detect and move along gradients in stiffness of an underlying substrate--a process known as durotaxis. The mechanisms underlying durotaxis are still unresolved, but generally believed to involve active sensing and locomotion. Here, we show that simple liquid droplets also undergo durotaxis. By modulating substrate stiffness, we obtain fine control of droplet position on soft, flat substrates. Unlike other control mechanisms, droplet durotaxis works without imposing chemical, thermal, electrical, or topographical gradients. We show that droplet durotaxis can be used to create large-scale droplet patterns and is potentially useful for many applications, such as microfluidics, thermal control, and microfabrication.

Case report: Pembrolizumab as an alternative to atezolizumab following a severe infusion reaction.

The emergence of immune-checkpoint inhibitors (ICIs) has revolutionized the field of oncology, providing promising results in various malignancies. However, ICIs can sometimes lead to severe injection reactions, requiring alternative treatment options. In this case report, we introduce a case of a severe infusion reaction induced by atezolizumab. After atezolizumab infusion, the patient experienced symptoms that were suggestive of anaphylactic shock, including chest tightness, low blood pressure, and loss of consciousness, all of which were restored by immediate administration of steroid, antihistamine, and epinephrine. When selecting a new ICI, we were concerned about cross-reactivity with atezolizumab. As such, we conducted a skin test to establish the underlying mechanism of the previous reaction to atezolizumab infusion, the results of which were highly suggestive of Ig-E-mediated hypersensitivity. The skin test for pembrolizumab, another ICI, was negative. Therefore, we replaced atezolizumab with pembrolizumab, and the infusion proceeded safely. To date, the patient has undergone 13 cycles of pembrolizumab, and the disease has remained stable. This case demonstrates that patients who exhibit severe injection reactions to ICIs can continue treatment safely, without cross-reactions, with alternative ICIs. This case will help provide patients who have experienced drug-related hypersensitivity reactions with a choice to use alternative ICIs, thus expanding their options for chemotherapy.

Universal phase dynamics in VO2 switches revealed by ultrafast operando diffraction.

Understanding the pathways and time scales underlying electrically driven insulator-metal transitions is crucial for uncovering the fundamental limits of device operation. Using stroboscopic electron diffraction, we perform synchronized time-resolved measurements of atomic motions and electronic transport in operating vanadium dioxide (VO2) switches. We discover an electrically triggered, isostructural state that forms transiently on microsecond time scales, which is shown by phase-field simulations to be stabilized by local heterogeneities and interfacial interactions between the equilibrium phases. This metastable phase is similar to that formed under photoexcitation within picoseconds, suggesting a universal transformation pathway. Our results establish electrical excitation as a route for uncovering nonequilibrium and metastable phases in correlated materials, opening avenues for engineering dynamical behavior in nanoelectronics.

Kaempferol Blocks the Skin Fibroblastic Interleukin 1ß Expression and Cytotoxicity Induced by 12-O-tetradecanoylphorbol-13-acetate by Suppressing c-Jun N-terminal Kinase.

Kaempferol, a bioflavonoid present in fruits and vegetables, has a variety of antioxidant and anti-inflammatory capacities, but the functional role of kaempferol in oxidative skin dermal damage has yet to be well studied. In this study, we examine the role of kaempferol during the inflammation and cell death caused by 12-O-tetradecanoylphorbol-13-acetate (TPA) in normal human dermal fibroblasts (NHDF). TPA (5 µM) significantly induced cytotoxicity of NHDF, where a robust increase in the interleukin (IL)-1ß mRNA among the various pro-inflammatory cytokines. The skin fibroblastic cytotoxicity and IL-1ß expression induced by TPA were significantly ameliorated by a treatment with 100 nM of kaempferol. Kaempferol blocked the production of the intracellular reactive oxygen species (ROS) responsible for the phosphorylation of c-Jun N-terminal kinase (JNK) induced by TPA. Interestingly, we found that kaempferol inhibited the phosphorylation of nuclear factor-kappa B (NF-κB) and the inhibitor NF-κB (IκBα), which are necessary for the expression of cleaved caspase-3 and the IL-1ß secretion in TPA-treated NHDF. These results suggest that kaempferol is a functional agent that blocks the signaling cascade of the skin fibroblastic inflammatory response and cytotoxicity triggered by TPA.

Air evolution during drop impact on liquid pool.

We elucidate the evolution of the entrained air in drop impact on a wide range of liquids, using ultrafast X-ray phase-contrast imaging. We elaborate the retraction mechanism of the entrapped air film in terms of liquid viscosity. We found the criterion for deciding if the entrapped air evolves into single or double bubbles, as determined by competition among inertia, capillarity, and viscosity. Low viscosity and low surface tension induce a small daughter droplet encapsulated by a larger air shell bubble, forming an antibubble. We demonstrate a phase diagram for air evolution regarding hydrodynamics.

Origin and dynamics of vortex rings in drop splashing.

A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row of vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.

Visualization of asymmetric wetting ridges on soft solids with X-ray microscopy.

One of the most questionable issues in wetting is the force balance that includes the vertical component of liquid surface tension. On soft solids, the vertical component leads to a microscopic protrusion of the contact line, that is, a 'wetting ridge'. The wetting principle determining the tip geometry of the ridge is at the heart of the issues over the past half century. Here we reveal a universal wetting principle from the ridge tips directly visualized with high spatio-temporal resolution of X-ray microscopy. We find that the cusp of the ridge is bent with an asymmetric tip, whose geometry is invariant during ridge growth or by surface softness. This singular asymmetry is deduced by linking the macroscopic and microscopic contact angles to Young and Neuman laws, respectively. Our finding shows that this dual-scale approach would be contributable to a general framework in elastowetting, and give hints to issues in cell-substrate interaction and elasto-capillary problems.

Electrical properties of dye-sensitized solar cells prepared by the binder-free TiO2 pastes.

Titania (TiO2) powder, which is material for photoelectrode in dye-sensitized solar cells (DSSCs), was fabricated by hydrothermal synthesis process at 230 degrees C for 12 hours. The crystal structures of all the synthesized nano-structured TiO2 films exhibited anatase phase. Binder-free pastes were prepared with the change of the amount of ammonia water from 2 µl to 640 µl in order to obtain the printable viscosity. It has been known that weak inter-particle bonds in slurry of flocculated particles make the slurry more viscous than slurry of dispersed particles. The increase of the amount of ammonia water for binder-free TiO2 pastes is attributed to the improvement of the viscosity of TiO2 paste and the power conversion efficiency of DSSCs using it. The viscosity of TiO2 pastes prepared at the ammonia water of 418 µl exhibited the highest value about 109,000 cP and also, was very transparent over 84%. As a result, the power conversion efficiency of DSSC prepared with the ammonia water of 418 µl was about 3%.

Size limits the formation of liquid jets during bubble bursting.

A bubble reaching an air-liquid interface usually bursts and forms a liquid jet. Jetting is relevant to climate and health as it is a source of aerosol droplets from breaking waves. Jetting has been observed for large bubbles with radii of R≫100 µm. However, few studies have been devoted to small bubbles (R<100 µm) despite the entrainment of a large number of such bubbles in sea water. Here we show that jet formation is inhibited by bubble size; a jet is not formed during bursting for bubbles smaller than a critical size. Using ultrafast X-ray and optical imaging methods, we build a phase diagram for jetting and the absence of jetting. Our results demonstrate that jetting in bubble bursting is analogous to pinching-off in liquid coalescence. The coalescence mechanism for bubble bursting may be useful in preventing jet formation in industry and improving climate models concerning aerosol production.