Revealing the role of electrons and phonons in the ultrafast recovery of charge density wave correlations in 1TT-TiSe2_2

Using time- and angle-resolved photoemission spectroscopy with selective near- and mid-infrared photon excitations, we investigate the femtosecond dynamics of the charge density wave (CDW) phase in 1$T$-TiSe$_2$, as well as the dynamics of CDW fluctuations at 240 K. In the CDW phase, we observe the coherent oscillation of the CDW amplitude mode. At 240 K, we single out an ultrafast component in the recovery of the CDW correlations, which we explain as the manifestation of electron-hole correlations. Our momentum-resolved study of femtosecond electron dynamics supports a mechanism for the CDW phase resulting from the cooperation between the interband Coulomb interaction, the mechanism of excitonic insulator phase formation, and electron-phonon coupling.Comment: 9 pages, 6 figure

Spatial patterns of organic matter content in the surface soil of the salt marshes of the Venice Lagoon (Italy)

Salt marshes are crucial eco-geomorphic features of tidal environments as they provide important ecological functions and deliver a wide range of ecosystem services. Being controlled by the interplay between hydrodynamics, geomorphology, and vegetation, the contribution of both organic matter (OM) and inorganic sediments drives salt marsh vertical accretion. This allows marshes to keep pace with relative sea level rise and likewise capture and store carbon, making them valuable allies in climate mitigation strategies. Thus, soil organic matter (SOM), i.e. the organic component of the soil, plays a key role within salt marsh environments, directly contributing to soil formation and supporting carbon storage. This study aims at inspecting spatial patterns of OM in surface salt marsh soils (top 20 cm), providing further insights into the physical and biological factors driving OM dynamics that affect salt marsh survival and carbon sink potential. Our results reveal two scales of variations in SOM content in marsh environments. At the marsh scale, OM variability is influenced by the interplay between surface elevation and changes in sediment supply linked with the distance from the marsh edge. At the system scale, OM content distribution is dominated by the gradient generated by marine and fluvial influence. The observed variations in SOM are explained by the combination of inorganic and organic input, preservation conditions, and sediment grain size. Our results highlight the importance of marshes as carbon sink environments, further emphasising that environmental conditions within a tidal system may generate strongly variable and site-specific carbon accumulation patterns, enhancing blue carbon assessment complexity.</p

Coherent Modulation of Quasiparticle Scattering Rates in a Photoexcited Charge-Density-Wave System

We present a complementary experimental and theoretical investigation of relaxation dynamics in the charge-density-wave (CDW) system TbTe3 after ultrafast optical excitation. Using time- and angle-resolved photoemission spectroscopy, we observe an unusual transient modulation of the relaxation rates of excited photocarriers. A detailed analysis of the electron self-energy based on a nonequilibrium Green's function formalism reveals that the phase space of electron-electron scattering is critically modulated by the photoinduced collective CDW excitation, providing an intuitive microscopic understanding of the observed dynamics

Effects Of Thermocycling And Light Source On The Bond Strength Of Metallic Brackets To Bovine Teeth

This study evaluated the effects of thermocycling and different light sources on the bond strength of metallic brackets to bovine tooth enamel using an adhesive resin. Bovine teeth were etched with 35% phosphoric acid gel for 20 s. After application of primer, metallic brackets were bonded to the buccal surface using Transbond XT, forming 8 groups (n=20), depending on the light source used for photoactivation (AccuCure 3000 argon laser - 20 s, Apollo 95E plasma arc - 12 s, UltraLume 5 LED - 40 s and XL2500 halogen light - 40 s) and experimental conditions without (Groups 1 to 4) or with thermocycling (Groups 5 to 8). Shear bond testing was carried out after 24 h of distilled water storage (Groups 1 to 4) or storage and thermocycling in distilled water (groups 5 to 8; 1,500 cycles - 5°/55°C). Data were subjected to two-way ANOVA and Tukey's test (α=0.05). The Adhesive Remnant Index (ARI) was evaluated at ×8 magnification. No significant differences (p>0.05) in bond strength were found when the conditions without and with thermocycling were compared for any of the light sources. No significant differences (p>0.05) in bond strength were found among the light sources, irrespective of performing or not thermocycling. There was a predominance of ARI scores 1 in all groups. In conclusion, light sources and thermocycling had no influence on the bond strength of brackets to bovine enamel.226486489Sfondrini, M.F., Cacciafesta, V., Scribante, A., Klersy, C., Plasma arc versus halogen light curing of orthodontic brackets: A 12-month clinical study of bond failures (2004) Am J Orthod Dentofacial Orthop, 125, pp. 342-347Dall'igna, C.M., Marchioro, E.M., Spohr, A.M., Mota, E.G., Effect of curing time on the bond strength of a bracket-bonding system cured with a light-emitting diode or plasma arc light (2011) Eur J Orthod, 33, pp. 55-59Correr, A.B., Sinhoreti, M.A., Sobrinho, L.C., Tango, R.N., Schneider, L.F., Consani, S., Effect of the increase of energy density on Knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc (2005) Braz Dent J, 16, pp. 218-224Cekic-Nagas, I., Egilmez, F., Ergun, G., The effect of irradiation distance on microhardness of resin composites cured with different light curing units (2010) Eur J Dent, 4, pp. 440-446Thind, B.S., Stirrups, D.R., Lloyd, C.H., A comparison of tungsten- quartz halogen, plasma arc and light-emitting diode light sources for the polymerization of an orthodontic adhesive (2006) Eur J Orthod, 28, pp. 78-82Filipov, I.A., Vladimirov, S.B., Residual monomer in a composite resin after light-curing with different sources, light intensities and spectra of radiation (2006) Braz Dent J, 17, pp. 34-38Park, J.K., Hur, B., Ko, C.C., García-Godoy, F., Kim, H.I., Kwon, Y.H., Effect of light-curing units on the thermal expansion of resin nanocomposites (2010) Am J Dent, 23, pp. 331-334Price, R.B., Labrie, D., Rueggeberg, F.A., Felix, C.M., Irradiance differences in the violet (405 nm) and blue (460 nm) spectral ranges among dental light-curing units (2010) J Esthet Restor Dent, 22, pp. 363-377Gonçalves, P.R.A., Moraes, R.R., Costa, A.R., Correr, A.B., Nouer, P.R.A., Sinhoreti, M.A.C., Effect of etching time and light source on the bond strength of metallic brackets to ceramic (2011) Braz Dent J, 22, pp. 245-248Swanson, T., Dunn, W.J., Childers, D.E., Taloumis, L.J., Shear bond strength of orthodontic brackets bonded with light-emitting diode curing units at various polymerization times (2004) Am J Orthod Dentofacial Orthop, 125, pp. 337-341Usumez, S., Buyukyilmaz, T., Karaman, A.I., Effect of light-emitting diode on bond strength of orthodontic brackets (2004) Angle Orthod, 74, pp. 259-263Talbot, T.Q., Blankenau, R.J., Zobitz, M.E., Weaver, A.L., Lohse, C.M., Rebellato, J., Effect of argon laser irradiation on shear bond strength of orthodontic brackets: An in vitro study (2000) Am J Orthod Dentofacial Orthop, 118, pp. 274-279Klocke, A., Korbmacher, H.M., Huck, L.G., Kahl-Nieke, B., Plasma arc curing lights for orthodontic bonding (2002) Am J Orthod Dentofacial Orthop, 122, pp. 643-648Bishara, S.E., Ostby, A.W., Laffoon, J.F., Warren, J., Shear bond strength comparison of two adhesive systems following thermocycling (2007) Angle Orthod, 77, pp. 337-341Faltermeier, A., Müssig, D., A comparative evaluation of bracket bonding with 1-, 2-, and 3-component adhesive systems (2007) Am J Orthod Dentofacial Orthop, 132, pp. 144.e1-144.e5Gale, M.S., Darvell, B.W., Thermal cycling procedures for laboratory testing of dental restorations (1999) J Dent, 27, pp. 89-99Trites, B., Foley, T.F., Banting, D., Bond strength comparison of 2 self-etching primers over a 3-month storage period (2004) Am J Orthod Dentofacial Orthop, 126, pp. 709-716Yuasa, T., Iijima, M., Ito, S., Muguruma, T., Saito, T., Mizoguchi, I., Effects of long-term storage and thermocycling on bond strength of two self-etching primer adhesive systems (2010) Eur J Orthod, 32, pp. 285-290Artun, J., Berglund, S., Clinical trials with crystal growth conditioning as an alternative to acid-etch enamel pretreatment (1984) Am J Orthod, 85, pp. 333-340Oesterle, L.J., Newman, S.M., Shellhart, W.C., Rapid curing of bondingcomposite with a xenon plasma arc light (2001) Am J Orthod Dentofacial Orthop, 119, pp. 610-616Staudt, C.B., Mavropoulos, A., Bouil, L.S., Kiliaridis, S., Krejcid, I., Light-curing time reduction with a new high-power halogen lamp (2005) Am J Orthod Dentofacial Orthop, 128, pp. 749-754Yu, H.S., Lee, K.J., Jin, G.C., Baik, H.S., Comparison of the shear bond strength of brackets using the LED curing light and plasma arc curing light: Polymerization time (2007) World J Orthod, 8, pp. 129-135Rueggeberg, F., Contemporary issues in photocuring (1999) Compend Contin Educ Dent Suppl, pp. 4-15de Munck, J., van Landuyt, K., Peumans, M., Poitevin, A., Lambrechts, P., Braem, M., A critical review of the durability of adhesion of tooth tissue: Methods and results (2005) J Dent Res, 84, pp. 118-132Reynolds, I.R., Composite filling materials as adhesives in Orthodontics (1975) Br Dent J, 138, p. 8

Hysteresis in the Random Field Ising Model and Bootstrap Percolation

We study hysteresis in the random-field Ising model with an asymmetric distribution of quenched fields, in the limit of low disorder in two and three dimensions. We relate the spin flip process to bootstrap percolation, and show that the characteristic length for self-averaging $L^*$ increases as $exp(exp (J/\Delta))$ in 2d, and as $exp(exp(exp(J/\Delta)))$ in 3d, for disorder strength $\Delta$ much less than the exchange coupling J. For system size $1 << L < L^*$, the coercive field $h_{coer}$ varies as $2J - \Delta \ln \ln L$ for the square lattice, and as $2J - \Delta \ln \ln \ln L$ on the cubic lattice. Its limiting value is 0 for L tending to infinity, both for square and cubic lattices. For lattices with coordination number 3, the limiting magnetization shows no jump, and $h_{coer}$ tends to J.Comment: 4 pages, 4 figure

Coherent, high repetition rate tender x-ray free-electron laser seeded by an extreme ultra-violet free-electron laser oscillator

A seeded FEL driven by a linac based on super conducting cavities, generating 108-1010 coherent photons per shot at 2-5 keV with 0.2-1 MHz of repetition rate, can address the need of a source devoted to fine analysis of matter using the linear spectroscopy technique. The seeding scheme described hereafter is a multi-stage cascade upshifting the radiation frequency by a factor 20-40. The x-ray range can be achieved with a seed constituted by a coherent flash in the extreme ultraviolet range provided by an FEL oscillator operating at 12-14 nm. The whole chain of x-ray generation is described by means of start-to-end three-dimensional simulations

Absence of toroidal moments in 'aromagnetic' anthracene

Colloidal suspensions of anthracene and other aromatic compounds have been shown to respond to a magnetic field as if they possessed a permanent magnetic moment. This phenomenon was named 'aromagnetism' by Spartakov and Tolstoi, and it was subsequently attributed to the interaction of an electric toroidal moment with a time-varying magnetic field. However, there has been no independent confirmation of the original work. Here, we have selected purified anthracene crystallites which respond to a low magnetic field and investigate how this response depends on the gradient and the time derivative of the field. We conclude that the anomaly cannot be attributed to a toroidal interaction but is due to a constant magnetic moment of the particles. Close examinations using magnetometry and scanning electron microscopy reveal metallic clusters of Fe and Ni up to a few hundred nanometres in size embedded in the anomalous crystallites. These inclusions represent 1.8 ppm by weight of the sample. The observed presence of ferromagnetic inclusions in the ppm range is sufficient to explain the anomalous magnetic properties of micron-sized anthracene crystals, including the reported optical properties of the colloidal suspensions

Influence of the incorporation of triclosan methacrylate on the physical properties and antibacterial activity of resin composite

The incorporation of antimicrobials in the composites as an attempt to reduce bacterial adhesion without jeopardizing mechanical properties is a challenge for Dentistry. Objective: To evaluate the bacterial adhesion and physical properties of a composite containing the methacrylate triclosan- derivative monomer (TM). Methodology: TM was synthesized and added to an experimental composite. Samples were divided into two groups: Control and TM (13.4 wt%). Antibacterial Activity: Three specimens of each material were prepared and placed on bacterial suspensions of Streptococcus mutans for 1, 5 and 10 days. After these periods the counting of the colonies (log10) was performed. Assays was performed in triplicate. Physical Properties: Three-body Abrasion (TBA): Ten specimens of each material were prepared and stored at 37°C/24 h. The surface roughness (Ra) and hardness (KHN) were analyzed. Next, the specimens were submitted to abrasive wear (30,000 cycles) and re-evaluated for Ra and KHN; Sorption/solubility (SS): cylindrical specimens (n=10) were prepared and weighted. The specimens were immersed in deionized water for 7 days at 37°C and then their weight was verified again. SS were calculated using accepted formulas; Diametral tensile strength (DTS): specimens (n=10) underwent test performed in an Instron universal testing machine at a crosshead speed of 1 mm/min. Data were submitted to appropriate statistical tests according to data distribution and assay (p&lt;0.05). Results: Bacterial Adhesion: TM showed a significant reduction on biofilm accumulation in the evaluated periods: 1 day (1.537±0.146); 5 days (2.183±0.138) and 10 days (4.469±0.155) when compared with Control: 1 day (4.954±0.249); 5 days (5.498±0.257) and 10 days (6.306±0.287). Physical Properties: For TBA, SS and DTS no significant difference was found between groups Control and TM. The incorporation of methacrylate triclosan-based monomer in the experimental composite reduce bacterial adhesion of S. mutans and did not affect important polymer properties.&nbsp

Recovery of NIS expression in thyroid cancer cells by overexpression of Pax8 gene

BACKGROUND: Recovery of iodide uptake in thyroid cancer cells by means of obtaining the functional expression of the sodium/iodide symporter (NIS) represents an innovative strategy for the treatment of poorly differentiated thyroid cancer. However, the NIS gene expression alone is not always sufficient to restore radioiodine concentration ability in these tumour cells. METHODS: In this study, the anaplastic thyroid carcinoma ARO cells were stably transfected with a Pax8 gene expression vector. A quantitative RT-PCR was performed to assess the thyroid specific gene expression in selected clones. The presence of NIS protein was detected by Western blot and localized by immunofluorescence. A iodide uptake assay was also performed to verify the functional effect of NIS induction and differentiation switch. RESULTS: The clones overexpressing Pax8 showed the re-activation of several thyroid specific genes including NIS, Pendrin, Thyroglobulin, TPO and TTF1. In ARO-Pax8 clones NIS protein was also localized both in cell cytoplasm and membrane. Thus, the ability to uptake the radioiodine was partially restored, associated to a high rate of efflux. In addition, ARO cells expressing Pax8 presented a lower rate of cell growth. CONCLUSION: These finding demonstrate that induction of Pax8 expression may determine a re-differentiation of thyroid cancer cells, including a partial recovery of iodide uptake, fundamental requisite for a radioiodine-based therapeutic approach for thyroid tumours