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Illuminating a magnetic material with femtosecond laser pulses induces complex ultrafast dynamical processes. The resulting optically detectable response usually contains contributions from both the optical properties and the magnetic degrees of freedom. Disentangling all the different components concurring to the generation of the total signal is a major challenge of contemporary experimental solid-state physics. Here, this problem is tackled, addressing the purely optical, nonmagnetic artifacts on the time resolved two-magnon stimulated Raman spectrum of an antiferromagnet, rationalizing the recent observation on the exchange energy modification upon photo-excitation. It is demonstrated how the genuine dynamics of the magnetic eigenmode can be disentangled from the nonlinear optical effects, generated by cross phase modulation, on the femtosecond timescale. The introduced approach can be extended for the investigation of

The time-resolved diffraction signal from a laser-excited solution has three principal components: the solute-only term, the solute-solvent cross term, and the solvent-only term. The last term is very sensitive to the thermodynamic state of the bulk solvent, which may change during a chemical reaction due to energy transfer from light-absorbing solute molecules to the surrounding solvent molecules and the following relaxation to equilibrium with the environment around the scattering volume. The volume expansion coefficient α for a liquid is typically ∼1×10-3 K-1, which is about 1000 times greater than for a solid. Hence solvent scattering is a very sensitive on-line thermometer. The decomposition of the scattered x-ray signal has so far been aided by molecular dynamics (MD) simulations, a method capable of simulating the solvent response as well as the solute term and solute/solvent cross terms for the data analysis. Here we present an experimental procedure, applicable to most hydrogen containing solvents, that directly measures the solvent response to a transient temperature rise. The overtone modes of OH stretching and CH3 asymmetric stretching in liquid methanol were excited by near-infrared femtosecond laser pulses at 1.5 and 1.7 μm and the ensuing hydrodynamics, induced by the transfer of heat from a subset of excited CH3OH* to the bulk and the subsequent thermal expansion, were probed by 100 ps x-ray pulses from a synchrotron. The time-resolved data allowed us to extract two key differentials: the change in the solvent diffraction from a temperature change at constant density, seen at a very short time delay ∼100 ps, and a term from a change in density at constant temperature. The latter term becomes relevant at later times ∼1 μs when the bulk of liquid expands to accommodate its new temperature at ambient pressure. These two terms are the principal building blocks in the hydrodynamic equation of state, and they are needed in a self-consistent reconstruction of the solvent response during a chemical reaction. We compare the experimental solvent terms with those from MD simulations. The use of experimentally determined solvent differentials greatly improved the quality of global fits when applied to the time-resolved data for C2H4I2 dissolved in methanol. [ABSTRACT FROM AUTHOR]

Inelastic x-ray scattering measurements of the dynamics structure factor have been performed on vitreous beryllium fluoride (v-BeF[sub 2]) at T=297 K in the momentum transfer, Q, range Q= 1.5-10 nm[sup -1]. We find evidence of well defined high frequency acoustic modes. The energy position and linewidth of the excitations disperse with Q as ∞ Q and ∞ Q², respectively, up to about one half of the first maximum of the static structure factor. Their magnitude compares favorably with low-frequency sound velocity and absorption data. The results indicate worth mentioning similarities of the high frequency collective dynamics of different network forming glasses such as v-B[sub 2]O[sub 3] and v-SiO[sub 2]. [ABSTRACT FROM AUTHOR]

Brillouin Light Scattering (BLS) spectroscopy is a non-invasive, non-contact, label-free optical technique that can provide information on the mechanical properties of a material on the sub-micron scale. Over the last decade it has seen increased applications in the life sciences, driven by the observed significance of mechanical properties in biological processes, the realization of more sensitive BLS spectrometers and its extension to an imaging modality. As with other spectroscopic techniques, BLS measurements not only detect signals characteristic of the investigated sample, but also of the experimental apparatus, and can be significantly affected by measurement conditions. The aim of this consensus statement is to improve the comparability of BLS studies by providing reporting recommendations for the measured parameters and detailing common artifacts. Given that most BLS studies of biological matter are still at proof-of-concept stages and use different--often self-built--spectrometers, a consensus statement is particularly timely to assure unified advancement.

The relentless pursuit of understanding matter at ever-finer scales has pushed optical microscopy to surpass the diffraction limit and realize super-resolution microscopy, which enables visualizing structures shorter than the wavelength of the light emitted by the sample. In the present work, we harnessed extreme ultraviolet beams to create sub-μm grating structures, which were revealed by extreme ultraviolet structured illumination microscopy. We establish that the resolution extension is achievable in the extreme ultraviolet, thereby opening the door to significant resolution enhancement, mainly defined by the wavelength employed.

Bladder mechanical properties are critical for organ function and tissue homeostasis. Therefore, alterations of tissue mechanics are linked to disease onset and progression. This study aims to characterize the tissue elasticity of the murine bladder wall considering its different anatomical components, both in healthy conditions and in actinic cystitis, a state characterized by tissue fibrosis. Here, we exploit Brillouin microscopy, an emerging technique in the mechanobiology field that allows mapping tissue mechanics at the microscale, in non-contact mode and free of labeling. We show that Brillouin imaging of bladder tissues is able to recognize the different anatomical components of the bladder wall, confirmed by histopathological analysis, showing different tissue mechanical properties of the physiological bladder, as well as a significant alteration in the presence of tissue fibrosis. Our results point out the potential use of Brillouin imaging on clinically relevant samples as a complementary technique to histopathological analysis, deciphering complex mechanical alteration of each tissue layer of an organ that strongly relies on mechanical properties to perform its function., (© 2024. The Author(s).)

Purpose: The purpose of this study is to determine whether and how learning American Sign Language (ASL) is associated with spoken English skills in a sample of ASL-English bilingual deaf and hard of hearing (DHH) children., Method: This cross-sectional study of vocabulary size included 56 DHH children between 8 and 60 months of age who were learning both ASL and spoken English and had hearing parents. English and ASL vocabulary were independently assessed via parent report checklists., Results: ASL vocabulary size positively correlated with spoken English vocabulary size. Spoken English vocabulary sizes in the ASL-English bilingual DHH children in the present sample were comparable to those in previous reports of monolingual DHH children who were learning only English. ASL-English bilingual DHH children had total vocabularies (combining ASL and English) that were equivalent to same-age hearing monolingual children. Children with large ASL vocabularies were more likely to have spoken English vocabularies in the average range based on norms for hearing monolingual children., Conclusions: Contrary to predictions often cited in the literature, acquisition of sign language does not harm spoken vocabulary acquisition. This retrospective, correlational study cannot determine whether there is a causal relationship between sign language and spoken language vocabulary acquisition, but if a causal relationship exists, the evidence here suggests that the effect would be positive. Bilingual DHH children have age-expected vocabularies when considering the entirety of their language skills. We found no evidence to support recommendations that families with DHH children avoid learning sign language. Rather, our findings show that children with early ASL exposure can develop age-appropriate vocabulary skills in both ASL and spoken English.

Hearing parents with deaf children face difficult decisions about what language(s) to use with their child. Sign languages such as American Sign Language (ASL) are fully accessible to deaf children, yet most hearing parents are not proficient in ASL prior to having a deaf child. Parents are often discouraged from learning ASL based in part on an assumption that it will be too difficult, yet there is little evidence supporting this claim. In this mixed-methods study, we surveyed hearing parents of deaf children ( n  = 100) who had learned ASL to learn more about their experiences. In their survey responses, parents identified a range of resources that supported their ASL learning as well as frequent barriers. Parents identified strongly with belief statements indicating the importance of ASL and affirmed that learning ASL is attainable for hearing parents. We discuss the implications of this study for parents who are considering ASL as a language choice and for the professionals who guide them., (© 2022 Walter de Gruyter GmbH, Berlin/Boston.)

Identifying the structural rearrangements during photoinduced reactions is a fundamental challenge for understanding from a microscopic perspective the dynamics underlying the functional mechanisms of heme proteins. Here, femtosecond stimulated Raman spectroscopy is applied to follow the ultrafast evolution of two different proteins, each bearing a six-coordinate heme with two amino acid axial ligands. By exploiting the sensitivity of Raman spectra to the structural configuration, we investigate the effects of photolysis and the binding of amino acid residues in cytochrome c and neuroglobin. By comparing the system response for different time delays and Raman pump resonances, we show how detailed properties of atomic motions and energy redistribution can be unveiled. In particular, we demonstrate substantially faster energy flow from the dissociated heme to the protein moiety in cytochrome c , which we assign to the presence of covalent heme-protein bonds.

Conjugated organic polymers based on substituted thiophene units are versatile building blocks of many photoactive materials, such as photochromic molecular switches or solar energy conversion devices. Unraveling the different processes underlying their photochemistry, such as the evolution on different electronic states and multidimensional structural relaxation, is a challenge critical to defining their function. Using femtosecond stimulated Raman scattering (FSRS) supported by quantum chemical calculations, we visualize the reaction pathway upon photoexcitation of the model compound 2-methyl-5-phenylthiophene. Specifically, we find that the initial wavepacket dynamics of the reaction coordinates occurs within the first ≈1.5 ps, followed by a ≈10 ps thermalization. Subsequent slow opening of the thiophene ring through a cleavage of the carbon-sulfur bond triggers an intersystem crossing to the triplet excited state. Our work demonstrates how a detailed mapping of the excited-state dynamics can be obtained, combining simultaneous structural sensitivity and ultrafast temporal resolution of FSRS with the chemical information provided by time-dependent density functional theory calculations.

Probing the structural rearrangement of a model photochromic molecular switch provides a window on the fundamental dynamics of electrocyclization reactions. Taking advantage of resonance-enhanced femtosecond stimulated Raman scattering (FSRS) with a broadly tunable Raman excitation wavelength, we selectively probe the competing dynamics of both the reactive and nonreactive conformers of a diarylethene (DAE) derivative that are simultaneously present in solution. Measurements that preferentially probe the electrocyclization (ring-closing) reaction of the reactive species reveal an unexpectedly slow nuclear rearrangement, stretching to tens of picoseconds, in striking contrast with the prompt electronic dynamics in the formation of the closed-ring isomer. The different results from transient electronic and vibrational spectroscopies reflect the different aspects of the reaction that are probed by each technique, depending on whether one considers the electronic state of the molecule or the structural rearrangement of the nuclei. Using a different Raman excitation wavelength selectively probes the picosecond-scale intersystem crossing dynamics of the nonreactive conformer, revealing the vibrational spectra of the singlet and triplet excited states for the first time. The present study paves the way to a more complete understanding of the structural mechanisms accompanying the reversible photochromic switching process.

We report the results of x-ray photon correlation spectroscopy (XPCS) experiments on multilayers of a photosensitive azo-polymer which can be softened by photoisomerization. Time correlation functions have been measured at different temperatures and momentum transfers (q) and under different illumination conditions (dark, UV or visible). The correlation functions are well described by the Kohlrausch-Williams-Watts (KWW) form with relaxation times that are proportional to q(-1). The characteristic relaxation times follow the same Vogel-Fulcher-Tammann law describing the bulk viscosity of this polymer. The out-of-equilibrium relaxation dynamics following a UV photoperturbation are accelerated, which is in agreement with a fluidification effect previously measured by rheology. The transient dynamics are characterized by two times correlation function, and dynamical heterogeneity is evidenced by calculating the variance χ of the degree of correlation as a function of ageing time. A clear peak in χ appears at a well defined time τ(C) which scales with q(-1) and with the ageing time, in a similar fashion as previously reported in colloidal suspensions [O. Dauchot, Phys. Rev. Lett. 95, 265701 (2005)]. From an accurate analysis of the correlation functions we could demonstrate a temperature and light dependent cross-over from compressed KWW to simple exponential behavior.

The effects of 6-keto-PGE1 on aggregatory responses to arachidonic acid (AA), adenosine diphosphate (ADP) and collagen were studied in human platelet-rich plasma (PRP). In addition, experiments were carried out to determine if these effects correlate with changes in platelet cyclic AMP and cyclic GMP levels. 6-Keto-PGE1 incubated in PRP produced dose-related increases in platelet cyclic AMP levels whereas platelet cyclic GMP levels were unchanged. Control aggregations induced by AA and ADP did not alter cyclic AMP and cyclic GMP levels whereas control aggregations induced by collagen elevated cyclic GMP levels with cyclic AMP were unchanged. 6-Keto-PGE1 produced a dose-dependent inhibition of platelet aggregation induced by AA, ADP and collagen and this inhibition correlated with a dose-related increase in cyclic AMP levels. Since 6-keto-PGE1 does not consistently alter cyclic GMP levels in human PRP, the present data support previous studies suggesting that 6-keto-PGE1 produces inhibition of platelet aggregation through the stimulation of cyclic AMP accumulation.