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(1) Introduction: The novel respiratory syndrome coronavirus 2 (SARS-CoV-2), also called coronavirus disease 2019 (COVID-19), is rapidly spreading in many countries and represents a public health emergency of international concern. The SARS-CoV-2 transmission mainly occurs from person-to-person via respiratory droplets (direct transmission route), leading to the onset of mild or severe symptoms or even causing death. Since COVID-19 is able to survive also on inanimate surfaces for extended periods, constituting an indirect transmission route, healthcare settings contaminated surfaces should be submitted to specific disinfection protocols. Our review aimed to investigate the existing disinfection measures of healthcare settings surfaces, preventing the nosocomial transmission of SARS-CoV-2. (2) Materials and Methods: We conducted electronic research on PubMed, Scopus, Science Direct, and Cochrane Library, and 120 items were screened for eligibility. Only 11 articles were included in the review and selected for data extraction. (3) Results: All the included studies proposed the use of ethanol at different concentrations (70% or 75%) as a biocidal agent against SARS-CoV-2, which has the capacity to reduce the viral activity by 3 log10 or more after 1 min of exposure. Other disinfection protocols involved the use of chlorine-containing disinfectant, 0.1% and 0.5% sodium hypochlorite, quaternary ammonium in combination with 75% ethanol, isopropyl alcohol 70%, glutardialdehyde 2%, ultraviolet light (UV-C) technology, and many others. Two studies suggested to use the Environmental Protection Agency (EPA)-registered disinfectants, while one article chooses to follow the WST-512-2016 Guidance of Environmental and Surfaces Cleaning, Disinfection and Infection Control in Hospitals. (4) Conclusion: Different surface disinfection methods proved to reduce the viral activity of SARS-CoV-2, preventing its indirect nosocomial transmission. However, more specific cleaning measures, ad hoc for the different settings of the healthcare sector, need to be formulated.

Pending the availability of vaccines to contain the SARS-CoV-2 pandemic, the current solution is &ldquo, social distancing&rdquo, with a reduction of dental treatments to those assessed as urgent and emergency cases. These treatments also involve Early Childhood Caries (ECC) due to the fact that this disease affects preschool children (a vulnerable population) and, in addition, shows a propensity to evolve into more serious complications (dental pain, infections). A narrative review was carried out to support a protocol for treating ECC with efficacious and safe (in terms of SARS-CoV-2 transmission) procedures. Protocol involves criteria for patients&rsquo, selection remotely (telemedicine), and well-detailed criteria/equipment and hygiene procedures to combat against SARS-CoV-2 transmission. Moreover, the protocol proposes innovative caries treatments, named Minimally Invasive Treatments (MITs), well known in pedodontics for their high level of children&rsquo, s acceptance during dental care. MITs allow for caries removal (particularly in primary teeth) without any high-speed rotating instrument cooled with nebulized air-water spray (with high risk of virus environmental diffusion), usually adopted during traditional treatments. For evaluating MITs effectiveness in caries management, only Systematic Review and Randomized Controlled Trials (RCTs) were included in our study, without any risk of bias assessment. The indications proposed in this protocol could support clinicians for the temporary management of ECC until the SARS-CoV-2 pandemic ends.

Dental caries and periodontal disease represent a health problem and a social cost for the entire population, and in particular for socio-economically disadvantaged individuals who are less resistant to disease. The aim of this review is to estimate the prevalence and severity of the two dental pathologies, caries and periodontal disease, in the different classes of socio-economically disadvantaged subjects and to understand which of them are most affected. A systematic search of the literature was performed in MEDLINE (via PubMed), EMBASE and Web of Science after establishing a suitable search strategy for each database, using keywords related to socio-economically vulnerable classes and health outcomes. Socio-economically disadvantaged individuals are more susceptible to tooth decay and periodontal disease (with relative tooth loss) than non-vulnerable people. Additionally, when multiple vulnerabilities are combined in the same subject, these oral diseases worsen. There is no type of vulnerability more affected by caries and periodontitis than others, since overall they all have severe disease indices. The data from this systematic literature review might be useful for health policy makers looking to allocate more resources and services to socially disadvantaged individuals, resulting in making them more resilient to oral disease due to their social marginalization.

Metal-insulator-semiconductor-insulator-metal (MISIM) heterostructures, with rectifying current-voltage characteristics and photosensitivity in the visible and near-infrared spectra, are fabricated and studied. It is shown that the photocurrent can be enhanced by adding a multi-walled carbon nanotube film in the contact region to achieve a responsivity higher than 100 &nbsp, mA &nbsp, W &minus, 1 under incandescent light of 0.1 &nbsp, mW &nbsp, cm &minus, 2 . The optoelectrical characteristics of the MISIM heterostructures are investigated at lower and higher biases and are explained by a band model based on two asymmetric back-to-back Schottky barriers. The forward current of the heterojunctions is due to majority-carrier injection over the lower barrier, while the reverse current exhibits two different conduction regimes corresponding to the diffusion of thermal/photo generated carriers and majority-carrier tunneling through the higher Schottky barrier. The two conduction regimes in reverse bias generate two plateaus, over which the photocurrent increases linearly with the light intensity that endows the detector with bias-controlled photocurrent.

Purpose The aim of this paper is to describe epidemiology and clinical manifestations of oral infection by Human papillomavirus (HPV), with particular attention to potential malignant lesions. Materials and methods A systematic review of the literature was conducted to describe the state of the art about HPV infection in oropharyngeal mucosa and its modalities of transmission, with particular attention to possible simultaneous infection in multiple anatomic sites. The aspects of prevention and control of infection by administering vaccines and the diffusion of sexual education campaigns are discussed also. Therapeutic protocols are also described where necessary. Results In recent years there has been a growing interest in HPV oral medicine, suggesting a role of such a family of viruses in the development of neoplasms of the oropharyngeal district as well as of the uterine cervix. Even if the mass media have increasingly faced the problem, causing frequent alarming among patients, the dentist therefore needs a complete and up-to-date knowledge of this infectious condition that is one of the most common causes of sexually transmitted mucous membrane infections (e.g. genital, anal and oral). Conclusions Recent studies about HPV infection are a basic requirement in order to promote the health of patients and provide them with the most exhaustive indications from dentists.

The aerosol produced during the use of dental instruments can spread pathogens potentially harmful to health. Most of the pathogens found in hydraulic system are Gram-negative aerobic heterotrophic environmental bacterial species exhibiting very low pathogenicity, although they may be of concern in the treatment of vulnerable patients, such as immunocompromised, medically compromised individuals and dental team. Dental team can be exposed to pathogenic microorganisms including cytomegalovirus, hepatitis B virus, hepatitis C virus, herpes simplex virus and Legionella spp. Legionella spp. are ubiquitous in hydraulic system, in fact surveys have shown that the percentage of samples taken at different dental chairs that were positive for Legionella spp. and ranged from 0 to 100%. The concentration of Legionella spp. in hydraulic system may reach 1000 organisms per ml. The primary route of Legionella spp. transmission is inhalation or aspiration of environmentally contaminated aerosols. All dentists are required to conduct a statutory risk assessment of their hydraulic system, in fact to comply with their legal duties, dentists must identify and assess the sources of risk and prepare a scheme for preventing and controlling risks. Moreover, they must monitor the quality of their hydraulic system at least annually to ensure that they are "legionellae free".

Photoreduction has so far received less attention than other approaches used to reduce graphene oxide (GO) like thermal and chemical reduction, although its potential is huge. The mechanism of deoxygenation is still questioned. In photolithographic applications, this means that one cannot predict whether the minimum feature size is close to the diffraction limit or larger. In this work we have studied GO photoreduction with vacuum ultraviolet Synchrotron radiation. GO has been exposed to extreme-UV and soft-X-ray radiation and the ratio between C–O and sp2 C–C bonds has been measured by photoemission spectroscopy as a function of dose and number of photons. The deoxygenation rate has been demonstrated to be proportional to the imaginary part f2 of the oxygen scattering factor. Experiments at the wavelengths where the f2 of oxygen is close to its maximum (namely close to 2 nm and between 20 nm and 60 nm) have demonstrated that GO can be rapidly reduced (even few minutes exposure time) with doses well below those needed for photothermal heating (the corresponding temperature rise is ∼1 μK) and without damaging the basal plane (the in-plane sp2 C–C bonds are not broken). Efficient nanometer scale GO photopatterning is therefore demonstrated to be possible.

Bulk heterojunction films made of polychiral single-walled carbon nanotubes (SWCNTs) form efficient heterojunction solar cells with n-type crystalline silicon (n-Si), due to their superior electronic, optical, and electrical properties. The films are multi-functional, since their hierarchical surface morphology provides a biomimetical anti-reflective, air-stable, and hydrophobic encapsulation for Si. Also, the films have a large effective area conferring them high optical absorption, which actively contribute to the solar energy harvesting together with Si. Here, we report photovoltaic devices with photoconversion efficiency up to 12% and a record 100% internal quantum efficiency (IQE). Such unprecedented IQE value is truly remarkable and indicates that every absorbed photon from the device, at some wavelengths, generates a pair of separated charge carriers, which are collected at the electrodes. The SWCNT/Si devices favor high and broadband carrier photogeneration; charge dissociation of ultra-fast hot excitons; transport of electrons through n-Si and high-mobility holes through the SWCNT percolative network. Moreover, by varying the film thickness, it is possible tailoring the physical properties of such a two-dimensional interacting system, therefore the overall device features. These results not only pave the way for low-cost, high-efficient, and broadband photovoltaics, but also are promising for the development of generic SWCNT-based optoelectronic applications.

Purpose To present the most frequent occult pathologies unexpectedly encountered via cone-beam computed tomography (CBCT), with particular reference to the diagnostic role of the dentist and that of the radiographer, with a view to clarifying where the diagnostic responsibility lies. Material and methods A narrative literature review on the most diffused occult pathologies under CBCT was conducted, with iconographical guide as an example for each category. Results The most frequent forms of unexpected pathologies encountered are: the presence of foreign bodies, airway anomaly, and the presence of radio-opacity or -transparency in the maxillofacial district. Conclusions The orthodontists must know that they are responsible to recognize these frequent, and potentially serious, pathologies of the head and neck. If the dentist feels unable to take on this responsibility, he or she should, however, be sure to have the scans read by a specialist radiologist.

Diagnosis of focal disease, the theory that the human oral microbial (HOM) could affect the onset and development of systemic diseases, was very popular in the past, but the lack of scientific evidence has led to the abandonment of this idea. Interestingly, increasing evidence over the past 3 or so decades suggests that HOM can indeed serve as a reservoir for systemic dissemination of pathogenic bacteria and their toxins in distant body sites, favouring the developments of malignant tumours. Malignant tumours are complex communities of oncogenically transformed cells with aberrant genomes, associated nonneoplastic cells including immune and stromal cells, and sometimes HOM, including bacteria and viruses. Recent data suggest that HOM and periodontal disease play an active role in the pathogenesis of colorectal cancer, in fact HOM has been found within the colorectal cancer microenvironment, and the composition of the HOM was different from that of adjacent non- neoplastic tissue. An association of fusobacterium nucleatum with the colonic mucosa of colorectal cancer has been proven. Several questions thus arise. Is periodontal disease a risk factor for colorectal carcinoma? Given the connectivity of the digestive tract, could fusubacterium nucleatum or other HOM be involved in additional gastrointestinal disorders? Furthermore, based on the “mobility” of Fusubacterium nucleatum and the omnipresence of cadherins, could this organism be involved in cancers beyond the gastrointestinal tract? Answers to these questions will shed new lights on the role of the HOM in onset of diseases.

The mechanisms responsible for phonon attenuation in glasses and in porous systems have been investigated. The acoustic attenuation has been measured by Brillouin light scattering using a Fabry-Perot apparatus and a new ultraviolet spectrometer. In particular, melt-quenched vitreous silica (ρ = 2200 kg m−3), silica xerogels with different densities (ρ = 510 ± 50, 770 ± 80, 1380 ± 140 and 2190 ± 200 kg m−3), and silica aerogel (ρ = 670 ± 80 kg m−3) have been studied. The porosities of the samples have been measured by nitrogen adsorption–desorption techniques. The Brillouin linewidth is found to increase with increasing pore size, being related to the effect of the growing structural disorder. Comparison between the acoustic attenuation obtained by the two wavelengths shows the existence of a crossover length a* which identifies the wave-vector values above which the disorder induced by the pore size starts to be the dominant cause of absorption. The position of the crossover is found to be frequency depen...

We have performed an inelastic X-ray scattering experiment on normal liquid H2 at a temperature of 31.5 K and a density of 21.5 nm-3 on the ID16 beam line at the European Synchrotron Radiation Facility. We compare three independent methods to determine experimentally its static structure factor S(Q): method (i) is from a diffraction measurement; method (ii) is through an omega integration of the dynamic structure factor S(Q, omega); method (iii) is from a best-fit procedure of the spectral line shape with a viscoelastic model. The measurements have then been compared with both classical and quantum path integral Monte Carlo simulations. The comparison between experimental and computed S(Q) indicates that quantum effects must be explicitly taken into account in the simulation in order to obtain good agreement with the data.

In this paper we accurately revisit the mechanical exfoliation and layer number determination of MoS2. By modelling the exfoliation itself as a random vertical (lateral) exfoliation (fragmentation) phenomenon, a rationale is given to optimise the number of iterations in the scotch-tape peeling technique and we rigorously demonstrate that since the second cleavage the occurrence of monolayers is the most likely. For the unambiguous layer number identification, experiments have been carried out with a unified complementary approach based on optical microscopy, atomic force microscopy, resonant and non resonant Raman spectroscopy, and photo-luminescence spectroscopy. The experimental analysis has been carried out on a statistically significant set of few-layer MoS2 flakes (from one to five layers). The work stresses the strong need of such complementary multi-technique approach to really unambiguously determine the layer number of flakes (that neither optical microscopy, nor AFM alone can give). Optical microscopy contrast analysis experiments (carried out on flakes deposited onto 270 nm SiO2/Si(1 0 0) substrates) demonstrate that for few-layer MoS2 (from the mono to the epta-layer) the optical contrast is weakly depending on the radiation wavelength and is a non-monotonic function of the layer number. Thus, flakes from ten to twelve layers exhibit the same contrast of monolayers, as demonstrated by parallel AFM analysis. AFM clearly shows that the stacking between the silicon oxide substrate and the first MoS2 layer is strongly unpredictable and likely depending on the degree of surface contamination of the substrate. A parallel systematic resonant Raman study is performed ranging from one to five layers clearly exhibiting systematic layer dependent spectral features in the one-five layers range. For the first time a layer estimation number based on a quantitative analysis of resonant Raman and PL spectra is proposed.

of the bone around the implants was observed. Conclusion Titanium needle impla­ nts can be used with immediate load­ ing in the posterior atrophic sector, especially in the elderly people, in the zone below the maxillary sinus, in the upper front area. They also give stability to other implants. In all cases, intra­oral welding is necessary and requires specific clinical train­ ing. Needle implants are not suitable for deep and wide ridges containing dense spongy bone.

Neutron-diffraction data on liquid iodine at three temperatures on the coexistence curve are presented. The data show that the strong orientational correlations between neighboring molecules, already found at the melting point, persist up to the vicinity of the critical point. The A2 effective pair potential model is found to describe satisfactorily the structure of the liquid along the entire coexistence curve.

The acoustic properties of highly concentrated H(2)SO(4) are investigated performing visible and ultraviolet Brillouin scattering measurements. We analyzed the isotropic and anisotropic spectra of this molecular liquid in a wide temperature and exchanged wavector range in order to study the evolution of its sound velocity and viscosity. This allows us to extract the parameters required to describe its viscoelastic relaxation behavior. We found that the behavior of the hydrodynamic parameters of this molecular liquid shares some similarities with that of water indicating a rather high increase of sound velocity if compared to that measured by ultrasonics.

We report a systematic investigation of the colour contrast (CC) of graphene (one, two and three layers) on 50, 72 and 80 nm thick Al(2)O(3)/Si(100) and 100 and 300 nm thick SiO(2)/Si(100). The CC is determined by the analysis of optical microscopy images taken under white light illumination. A corresponding assignment of graphene in the single-layer, double-layer and trilayer phases is made using micro-Raman spectroscopy. A quantitative evaluation allows us to conclude that the colour contrast between 72 nm alumina and graphene is significantly larger than that between 300 nm silicon oxide and graphene (by factors of 2.2, 2.0 and 3.3 for the single-layer, double-layer and trilayer graphene flakes respectively). Moreover, data indicate that, to increase visibility, the use of a red or a green light is preferable.

We have used Raman spectroscopy, transmission electron microscopy, x-ray diffraction, and x-ray photoemission spectroscopy to investigate strain relaxation mechanism of Si(0.22)Ge(0.78) heteroepitaxial layer deposited on Si substrates in tensile, neutral, and compressive strain conditions. The three regimes have been obtained by interposing between the SiGe layer and the substrate a fully relaxed Ge layer, a partially relaxed Ge layer, or growing directly the alloy on Si. We found that the deposition of a Ge buffer layer prior to the growth of the SiGe is very promising in view of the realization of thin virtual substrates on silicon to be used for the deposition of strain-controlled high Ge content SiGe alloys. We demonstrate that this is mainly due to the strain relaxation mechanism in the Ge layer occurring via insertion of pure edge 90 degrees misfit dislocations (MDs) and to the confinement of threading arms in to the Ge layer due to a second MD network formed at the SiGe/Ge heterointerface.

Purpose To assess the changes in bacterial profile along the transmucosal path of healing screws placed immediately after insertion of two-piece endosseus implants during the 4-month osseointegration phase, in absence of functional load. Materials and methods Two site-specific samples were collected at the peri-implant mucosa of the healing screws of 80 two-piece implants, for a total of 640 samples. Implants placement was performed following a single protocol with flapless technique, in order to limit bacterial contamination of the surgical site. Identical healing screws (5 mm diameter/4 mm height) were used for each of the 80 implants. During the 4 months of the study, the patients followed a standard oral care regimen with no special hygiene maneuvers at the collection sites. Results The present research documents that during the 4-month period prior to application of function load the bacterial profile of all sites exhibited a clear prevalence of cocci at the interface between implant neck and osteoalveolar crest margin. Conclusions A potentially pathogenic bacterial flora developed only along the peri-implant transmucosal path.

International audience; The recently developed technique of Brillouin ultraviolet scattering is used to measure phonon dispersion and damping in the prototypical strong glass v-SiO2. Results on the low temperature, T ~ 10 – 100 K, sound attenuation at a frequency around 66 GHz are presented. The comparison between a model which takes into account dynamical processes (thermally activated relaxations and the interaction with the bath of thermal vibrations) and the experimental data indicates the presence of a strong static contribution in the region explored by ultraviolet radiation supporting the presence of a transition between static and dynamic attenuation mechanisms at a frequency around 100 GHz.

We report ultraviolet Brillouin light-scattering experimental data on $v\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2}$ in an unexplored frequency region, performed with a newly available spectrometer, up to exchanged wave vector $q$ values of $0.075\phantom{\rule{0.3em}{0ex}}{\mathrm{nm}}^{\ensuremath{-}1}$, at different temperatures. The measured attenuation follows a ${q}^{2}$ law and is temperature dependent. Such temperature dependence is found to be in good agreement with that measured at lower $q$, suggesting that the broadening of the Brillouin peak is mainly due to a dynamic attenuation mechanism. The comparison of the present data with those obtained by inelastic x-ray and visible scattering indicates the existence of a crossover among different attenuation mechanisms, whose nature is briefly discussed.

We present a multiple-grating spectrometer designed for high-resolution and high-contrast low-frequency scattering spectroscopy in the ultraviolet, as well as in the visible spectral regions. The instrument has a resolution better than 1 GHz and a contrast of about 1×10−10 both in the visible and in the UV range, thus doubling the highest resolution achieved by double-monochromator double-pass spectrometers such as the SOPRA DMDP2000, conceived for Raman–Brillouin spectroscopy using visible excitation. Performance tests and the Brillouin spectra obtained in the ultraviolet range are reported. Ray tracing results, aiming to give a better insight on the instrument performances are also presented. The instrument opens the possibility to study a new region of the exchanged momentum with a suitable energy resolution and to investigate the spectrum of density fluctuations in materials where the UV penetration depth could be a relevant step for the experimental study of the dynamics of disordered material.

The principles of the Double Difference (DD) method, applied to the neutron spectrometer VESUVIO, are discussed. VESUVIO, an inverse geometry spectrometer operating at the ISIS pulsed neutron source in the eV energy region, has been specifically designed to measure the single particle dynamical properties in condensed matter. The width of the nuclear resonance of the absorbing filter, used for the neutron energy analysis, provides the most important contribution to the energy resolution of the inverse geometry instruments. In this paper, the DD method, which is based on a linear combination of two measurements recorded with filter foils of the same resonance material but of different thickness, is shown to improve significantly the instrumental energy resolution, as compared with the Single Difference (SD) method. The asymptotic response functions, derived through Monte-Carlo simulations for polycrystalline Pb and ZrH2 samples, are analysed in both DD and SD methods, and compared with the experimental ones for Pb sample. The response functions have been modelled for two distinct experimental configurations of the VESUVIO spectrometer, employing 6Li-glass neutron detectors and NaI gamma detectors revealing the gamma-ray cascade from the (n, gamma) reaction, respectively. The DD method appears to be an effective experimental procedure for Deep Inelastic Neutron Scattering measurements on VESUVIO spectrometer, since it reduces the experimental resolution of the instrument in both 6Li-glass neutron detector and gamma detector configurations.

Brillouin light scattering spectra from transverse and longitudinal acoustic waves in liquid and supercooled 3-methylpentane have been collected from room temperature down to 80 K, just above the glass transition. Spectra at different wave vectors have been obtained using 532 nm and 266 nm excitation. We found evidence of a shear relaxation with a characteristic time of 100 s at the glass transition which only partly accounts for the relaxation observed in the propagation and attenuation of the longitudinal modes. The inclusion of a relaxing bulk viscosity contribution with a relaxation time of the order of 10(2) ns at the glass transition is found to adequately reproduce the experimental data including transient grating data at a much lower frequency. A consistent picture of relaxed shear and bulk moduli as a function of temperature is derived. These two quantities are found to be related by a linear relation suggesting that a Cauchy-like relation holds also above the glass transition.

Recent experimental results obtained on normal and deuterated water using light-scattering spectroscopy from Brillouin to librational Raman frequencies are reviewed. Particular attention is devoted to the librational mode region and to the Rayleigh wing where both new measurements (including depolarization ratio measurements and absolute intensities analysis) and computer simulation have pointed out the importance of “interaction-induced” scattering contributions in interpreting quantitatively this low-frequency part of the spectrum. The agreement between experimental and simulated data extends up to the 400 wavenumbers band, excluding the presence of direct electronic disturbances created by hydrogen-bond formation dynamics in this spectral region.

In this paper we present a comparative study of the agglomeration process in silicon-on-insulator (SOI), silicon germanium-om-insulator (SGOI), and strained SOI (SSOI) thin layers under thermal annealing in ultrahigh vacuum. In particular, we provide the first evidence and characterization of agglomeration in SGOI and SSOI substrates. A common agglomeration dynamics is observed in all the substrates investigated, with the semiconductor-on-insulator layer thickness being the main parameter governing it. These findings provide a better understanding of the surface-energy-driven dewetting phenomenon in semiconductor layers and allow us to single out the influence of the surface and stress energies on the void formation and evolution, as well as on the size and density of the agglomerated islands. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3117837]

Brillouin spectral line shapes of n‐pentanol have been measured from −75.5 °C (close to the melting point) up to 115 °C (close to the boiling point) using a grating monochromator. The instrument, owing to its very high resolution, contrast, and free spectral range, has been preferred to the usually employed Fabry–Perot interferometer. The spectra, fitted with a single relaxation generalized hydrodynamic theory, support the existence of a high frequency relaxation process with an activation energy of about 9 KJ/mol. This relaxation process, which should be related to isomeric rotational relaxation, is well separated at low temperature from the structural relaxation observed at lower frequencies in ultrasonic experiments.

International audience; The acoustic attenuation of vitreous germania (v-GeO2) has been measured over more than three decades in frequency, by means of neutron scattering at high-frequency (THz), visible light scattering and the newly developed technique of Brillouin ultraviolet scattering at lower frequencies (15-50 GHz). The experiments are supported by a molecular dynamics study of a simulated sample of v-GeO2. The temperature dependence, from 80K up to the glass transition temperature, shows a persistence of the dynamical nature of the attenuation in the GHz range and a simultaneous increase of the contribution coming from the structural disorder. At higher frequencies clear evidences of a crossover to a region where the attenuation is induced only by the topological disorder are found.

Room temperature rotational Raman spectra of N2 in the 56–135 amagat density range are employed to test the memory function approach to rotational dynamics. Memory functions of order one and two in the Mori hierarchy are derived from the spectra and compared with the corresponding calculated free rotor memory functions. It is found that the free rotor memory function multiplied by a decaying function approximately reproduces the experimental curves, the degree of approximation being sensibly better for the second order memory function. Exponentially decaying functions are required to reproduce the long time behaviour of both experimental memory functions. At short times a gaussian decay is found to be more adequate for the first order memory function. Decay parameter values are discussed and compared with available theories.

Polarized and depolarized room temperature light scattering spectra of normal alcohols from methanol to pentanol have been measured up to 80 cm−1 frequency shift. At low frequency shifts (smaller than 4 cm−1), resolutions as high as 0.04 cm−1 have been used. The possibility of using the same spectrometer for measuring both low frequency Brillouin structures and high frequency depolarized tails allows for the first time a precise determination of both lineshapes and relative integrated intensities between the various spectral components. The experimental results are presented and briefly discussed on the basis of the existing theories for depolarized scattering from molecular liquids.

An interpretation of the low frequency Raman scattering in all disordered systems including liquids is suggested in terms of phononlike excitations damped by anharmonicity and by structural relaxations. In principle, owing to the disorder‐induced breakdown of the k vector selection rule, all of these excitations are allowed to participate to the scattering process. An ad hoc simplified model is also proposed to calculate the low frequency Raman scattering, and it is found to reproduce at least qualitatively the main features of the depolarized spectrum in amorphous solid and liquid 10M KOH water solutions at different temperatures.