Frequency-Dependent Squeezed Vacuum Source for the Advanced Virgo Gravitational-Wave Detector

In this Letter, we present the design and performance of the frequency-dependent squeezed vacuum source that will be used for the broadband quantum noise reduction of the Advanced Virgo Plus gravitational-wave detector in the upcoming observation run. The frequency-dependent squeezed field is generated by a phase rotation of a frequency-independent squeezed state through a 285 m long, high-finesse, near-detuned optical resonator. With about 8.5 dB of generated squeezing, up to 5.6 dB of quantum noise suppression has been measured at high frequency while close to the filter cavity resonance frequency, the intracavity losses limit this value to about 2 dB. Frequency-dependent squeezing is produced with a rotation frequency stability of about 6 Hz rms, which is maintained over the long term. The achieved results fulfill the frequency dependent squeezed vacuum source requirements for Advanced Virgo Plus. With the current squeezing source, considering also the estimated squeezing degradation induced by the interferometer, we expect a reduction of the quantum shot noise and radiation pressure noise of up to 4.5 dB and 2 dB, respectively.

Water-like Behavior of Formamide: Jump Reorientation Probed by Extended Depolarized Light Scattering

Water is a strong self-associated liquid with peculiar properties that crucially depend on H-bonding. As regards its molecular dynamics, only recently has water reorientation been successfully described based on a jump mechanism, which is responsible for the overall H-bonding exchange. Here, using high-resolution broad-band depolarized light scattering, we have investigated the reorientational dynamics of formamide (FA) as a function of concentration from the neat liquid to diluted aqueous solutions. Our main findings indicate that in the diluted regime the water rearrangement can trigger the motion of FA solute molecules, which are forced to reorient at the same rate as water. This highlights an exceptional behavior of FA, which perfectly substitutes water within its network. Besides other fundamental implications connected with the relevance of FA, its water-like behavior provides rare experimental evidence of a solute whose dynamics is completely slaved to the solvent.

Molecular properties of aqueous solutions: a focus on the collective dynamics of hydration water

When a solute is dissolved in water, their mutual interactions determine the molecular properties of the solute on one hand, and the structure and dynamics of the surrounding water particles (the so-called hydration water) on the other. The very existence of soft matter and its peculiar properties are largely due to the wide variety of possible water-solute interactions. In this context, water is not an inert medium but rather an active component, and hydration water plays a crucial role in determining the structure, stability, dynamics, and function of matter. This review focuses on the collective dynamics of hydration water in terms of retardation with respect to the bulk, and of the number of molecules whose dynamics is perturbed. Since water environments are in a dynamic equilibrium, with molecules continuously exchanging from around the solute towards the bulk and vice versa, we examine the ability of different techniques to measure the water dynamics on the basis of the explored time scales and exchange rates. Special emphasis is given to the collective dynamics probed by extended depolarized light scattering and we discuss whether and to what extent the results obtained in aqueous solutions of small molecules can be extrapolated to the case of large biomacromolecules. In fact, recent experiments performed on solutions of increasing complexity clearly indicate that a reductionist approach is not adequate to describe their collective dynamics. We conclude this review by presenting current ideas that are being developed to describe the dynamics of water interacting with macromolecules.

Aqueous solvation of amphiphilic molecules by extended depolarized light scattering: the case of trimethylamine-N-oxide

Hydrophilic and hydrophobic interactions strongly affect the solvation dynamics of biomolecules. To understand their role, small model systems are generally employed to simplify the investigations. In this study the amphiphile trimethylamine N-oxide (TMAO) is chosen as an exemplar, and studied by means of extended frequency range depolarized light scattering (EDLS) experiments as a function of solute concentration. This technique proves to be a suitable tool for investigating different aspects of aqueous solvation, being able at the same time to provide information about relaxation processes and vibrational modes of solvent and solute. In the case study of TMAO, we find that the relaxation dynamics of hydration water is moderately retarded compared to the bulk, and the perturbation induced by the solute on surrounding water is confined to the first hydration shell. The results highlight the hydrophobic character of TMAO in its interaction with water. The number of molecules taking part in the solvation process decreases as the solute concentration increases, following a trend consistent with the hydration water-sharing model, and suggesting that aggregation between solute molecules is negligible. Finally, the analysis of the resonant modes in the THz region and the comparison with the corresponding results obtained for the isosteric molecule tert-butyl alcohol (TBA) allow us to provide new insights into the different solvating properties of these two biologically relevant molecules.

Painting biological low-frequency vibrational modes from small peptides to proteins

We use experiments and simulation to investigate the validity of different model systems used to study the low-frequency vibrations of proteins.

Heat-denatured lysozyme aggregation and gelation as revealed by combined dielectric relaxation spectroscopy and light scattering measurements

The dielectric behavior of native and heat-denatured lysozyme in ethanol-water solutions was examined in the frequency range from 1 MHz to 2 GHz, using frequency-domain dielectric relaxation spectroscopy. Because of the conformational changes on unfolding, dielectric methods provide information on the denaturation process of the protein and, at protein concentration high enough, on the subsequent aggregation and gelation. Moreover, the time evolution of the protein aggregation and gelation was monitored measuring, by means of dynamic light scattering methods, the diffusion coefficient of micro-sized polystyrene particles, deliberately added to the protein solution, which act as a probe of the viscosity of the microenvironment close to the particle surface. All together, our measurements indicate that heat-induced denaturation favors, at high concentrations, a protein aggregation process which evolves up to the full gelation of the system. These findings have a direct support from IR measurements of the absorbance of the amide I band that, because of the unfolding, indicate that proteins entangle each other, producing a network structure which evolves, in long time limit, in the gel.

Mercury acetate produced by metallic mercury subjected to acoustic cavitation in a solution of acetic acid in water

Mercury acetate (MA) can be obtained by metallic mercury immersed in a mixture of deionised, bidistillated water (dbw) and acetic acid. We show that MA crystallization time is drastically reduced if the previous mixtures are subjected to acoustic cavitation. The largest quantity of crystals is obtained by a concentration of acetic acid of about 7% in volume. NMR analysis of identical mixtures in the presence of mercury, performed as soon as possible after cavitation, showed the largest quantity of mercury acetate molecules, for the same concentration of acetic acid of 7% in volume.

Transmittance Fourier transform infrared spectra of liquid water in the whole mid-infrared region: temperature dependence and structural analysis

Transmittance Fourier transform infrared (FT-IR) spectra of liquid water in the 4-80 degrees C temperature range are reported in the whole mid-infrared (MIR) region (4000-360 cm (-1)). The spectra were recorded by using a newly developed, home-made transmittance cell, working in light vacuum conditions (pressures of the order of 3-4 millibar). This permits the elimination of the aqueous vapor bands from the liquid spectra, particularly in the bending region, and the rapid collection of data without fluxing large amounts of nitrogen through the interferometer sample chamber. The temperature evolution of the OH stretching and HOH deformation bands is discussed in terms of Gaussian components analysis and a two-state model describing the equilibrium between different H-bond structures of liquid water. From this picture, structural and thermodynamic information about the hydrogen-bonding network of water is obtained.

Liposome-based formulations for the antibiotic nonapeptide Leucinostatin A: Fourier transform infrared spectroscopy characterization and in vivo toxicologic study

Leucinostatin-A is a nonapeptide isolated from Paecilomyces marquandii, Paecilomyces lilacinus A257, and Acremonium sp., exerting remarkable phytotoxic, antibacterial (especially against Gram-positive) and antimycotic activities. With the aim to find alternative formulation for in vivo administration, a number of Leucinostatin-A-loaded liposomal formulations have been prepared and characterized. Both large unilamellar vesicles and multilamellar vesicles consisting of synthetic and natural lipids were evaluated. In addition, to determine the nature of peptide-membrane interactions and the stability of liposomes loaded with Leucinostatin-A, a Fourier Transform Infrared Spectroscopy study was performed. The results suggest that the mode of interaction of the peptide is dependent on its concentration, on bilayer fluidity, and on liposome type. Finally, the LD50 of both free and liposome-delivered Leucinostatin-A was determined in mice. These results suggest that the incorporation of Leucinostatin-A into liposomes may result in decreased Leucinostatin-A toxicity, as the intraperitoneal administration of Leucinostatin-A-loaded liposomes reduced the LD50 of Leucinostatin-A 15-fold.

[Ascites in chronic pancreatitides. Report of 2 cases]

2 cases of alcoholic chronic pancreatitis complicated by ascites are described. Both presented a cystic formation in the pancreas. In the first, a direct communication existed between the cystic and peritoneal cavities with passage of pancreatic secretion and serous membrane inflammatory reaction. The literature shows that this mechanism is the one most frequently responsible for ascites in chronic pancreatitis. For diagnosis, demonstration of high amylase and proteins in the ascitic fluid was decisive. Internal drainage of the cyst carried out in one of the two cases resolved the picture.