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By directly altering microscopic interactions, pressure provides a powerful tuning knob for the exploration of condensed phases and geophysical phenomena1. The megabar regime represents an interesting frontier, in which recent discoveries include high-temperature superconductors, as well as structural and valence phase transitions2–6. However, at such high pressures, many conventional measurement techniques fail. Here we demonstrate the ability to perform local magnetometry inside a diamond anvil cell with sub-micron spatial resolution at megabar pressures. Our approach uses a shallow layer of nitrogen-vacancy colour centres implanted directly within the anvil7–9; crucially, we choose a crystal cut compatible with the intrinsic symmetries of the nitrogen-vacancy centre to enable functionality at megabar pressures. We apply our technique to characterize a recently discovered hydride superconductor, CeH9(ref. 10). By performing simultaneous magnetometry and electrical transport measurements, we observe the dual signatures of superconductivity: diamagnetism characteristic of the Meissner effect and a sharp drop of the resistance to near zero. By locally mapping both the diamagnetic response and flux trapping, we directly image the geometry of superconducting regions, showing marked inhomogeneities at the micron scale. Our work brings quantum sensing to the megabar frontier and enables the closed-loop optimization of superhydride materials synthesis.

This is the first projection of marine circulation and biogeochemistry for the Ascension Island Marine Protected Area (AIMPA). Marine Protected Areas are a key management tool used to safeguard biodiversity, but their efficacy is increasingly threatened by climate change. To assess an MPA's vulnerability to climate change and predict biological responses, we must first project how the local marine environment will change. We present the projections of an ensemble from the Sixth Coupled Model Intercomparision Project. Relative to the recent past (2000–2010), the multi‐model means of the mid‐century (2040–2050) project that the AIMPA will become warmer (+0.9 to +1.2°C), more saline (+0.01 to +0.10), with a shallower mixed layer depth (−1.3 to −0.8 m), a weaker Atlantic Equatorial Undercurrent (AEU) (−1.5 to −0.4 Sv), more acidic (−0.10 to −0.07), with lower surface nutrient concentrations (−0.023 to −0.0141 mmol N m−3and −0.013 to −0.009 mmol P m−3), less chlorophyll (−6 to −3 µg m−3) and less primary production (−0.31 to −0.20 mol m−2yr−1). These changes are often more extreme in the scenarios with higher greenhouse gases emissions and more significant climate change. Using the multi‐model mean for two scenarios in the years 2090–2100, we assessed how five key ecosystem services in both the shallow subtidal and the pelagic zone were likely to be impacted by climate change. Both low and high emission scenarios project significant changes to the AIMPA, and it is likely that the provision of several ecosystem services will be negatively impacted. Ascension Island is a small remote volcanic island in the equatorial Atlantic Ocean. The seas around Ascension Island have been protected from commercial fishing since 2019. We used the marine component of computer simulations of the Earth's climate to try to understand the future of the Ascension Island Marine Protected Area (AIMPA). Over the next century, the AIMPA region will become warmer, more saline, more acidic, less productive, and with lower nutrient and chlorophyll concentrations in the surface waters. The most important current of the region, the Atlantic Equatorial Current, is also projected to weaken in all scenarios. These changes are likely to negatively impact the ability of the AIMPA to provide ecosystem services such as healthy ecosystems, fish stocks, the removal of carbon dioxide from the air, and attract tourism. This work is important because it is the first projection of the climate around the AIMPA since it was created, and it has allowed local policymakers to understand how the changing climate is likely to affect their environment and ecosystem services. We present the first projection of the future marine circulation and biogeochemistry of the Ascension Island Marine Protected Area (AIMPA)The AIMPA will become warmer, more saline, more acidic, with less surface nutrients, primary production and chlorophyllThe AIMPA's capacity to provide ecosystem services will be significantly negatively impacted under a high emission scenario We present the first projection of the future marine circulation and biogeochemistry of the Ascension Island Marine Protected Area (AIMPA) The AIMPA will become warmer, more saline, more acidic, with less surface nutrients, primary production and chlorophyll The AIMPA's capacity to provide ecosystem services will be significantly negatively impacted under a high emission scenario

Thymic malignancies are rare tumors with few therapeutic options. The STYLE trial was aimed to evaluate activity and safety of sunitinib in advanced/recurrent type B3 thymoma (T) and thymic carcinoma (TC).

Shock compression experiments carried out at Livermore using liquid deuteriurn have measured the Hugoniot and shock temperature to pressures up to 3.2 Mbar. In the region between 4000 K to 10,000 K the prediction of small or negative values of (dP/dT)vsuggests that the molecular fluid dissociates into a mixture containing a significant fraction of string-like matter. In the temperature range from 20.000 to 50,000 K the fluid may be treated as a nearly degenerate liquid metal. Above 50,000 K electronic excitation becomes significant and the fluid must be treated as a a dense plasma. There appears to be no experimental evidence in favor of a f irst order phase transition in the fluid.

An X-ray study was performed on powder specimens and on stretched oriented fibres of a smectic polyacrylate. The X-ray diffraction patterns showed the existence of monolayer smectic A and bilayer smectic C mesophases that coexisted over a well defined range of temperature. In the latter mesophase the mesogenic groups were titled with respect to the smectic layer normal by an angle β≈30○. The electron density profile ρ(z) along the direction normal to the smectic layers in the smectic C mesophase was determined by Fourier inversion and indicated the presence of a minor interdigitation of the terminal substituents. The phase problem related to the Fourier inversion was solved by using a pattern recognition approach based on the histogram of the electron density map. The positional smectic layer order parameters were also calculated for the first five harmonics of the positional distribution function of the smectic layers and their values suggested a well ordered layer structure.

We have studied the relative stability of the [MATH] and [MATH] stackings of stage 1 lithium in graphite at zero temperature, focusing on the Li-C chemical bond in each case. We have determined the equilibrium atomic structure of LiC6with a first-principles molecular dynamics technique, in particular for the Li atoms equilibrium positions, and the effect of Li-intercalation on the graphite planes. We found that the [MATH] stacking is favorable, although the energy difference turns out to be quite small. A very slight distortion of the graphite lattice gives rise to two different classes of hexagonal rings, depending on whether they are occupied by lithium atoms.

Background: GPR7, the endogenous coupled receptor for neuropeptide B and neuropeptide W, is expressed in several regions of the central nervous system, which are involved in the regulation of feeding behavior. GPR7 affects the regulation of energy balance through a mechanism independent of leptin and melanocortin pathways. Aim:Aim of this study was to investigate whether GPR7gene mutations can be detected in human subjects and, in that event, if they are differently distributed among lean and obese subjects. Subjects and methods:The coding region of GPR7were sequenced in 150 obese patients and 100 normal-weight unrelated controls. Functional studies of the allelic variants were performed. Results:One genetic GPR7 variant was found (Tyr135Phe — rs33977775) in obese subjects (13.3%) and lean control (25%). Functional studies did not reveal significant differences between the wild type and the Tyr135Phe allelic variants in their NPW-mediated capacity to inhibit forskolin-induced cAMP production. Conclusions:Screening of GPR7 gene mutations among lean and obese subjects revealed a Tyr135Phe allelic variant that was fairly common in the study population. As indicated by in vitroand in silicostudies, this variant is unlikely to cause a functional derangement of the receptor.

This paper studies the influence of different urban coverings (green areas or dry cover) on the urban microclimate. Different urban structures in a small area show different microclimatic behavior, depending on the thermophysical properties of the surface materials, in particular on the presence and extent of green areas. The research has been developed in downtown Rome in the summer period. In order to evaluate the impact of different urban envelopes, a typical urban square has been considered and analyzed systematically with the microscale climate model ENVI-met. A number of simulations has been performed with various kinds of surface covers and of vegetation and their effect on the air and soil temperatures and on the surface heat fluxes has been determined.

Most of dialysis patients present components of frailty: comorbidities, disabilities, dependence, malnutrition, cognitive impairment, and poor social conditions. Frailty is suspected to affect the quality of life (QoL) of dialysis patients. This study aims to evaluate this relation. Little is available in the Literature on this topic.We enrolled 203 out of 233 prevalent dialysis patients in the Trieste area. We administered to them the Short-Form 36 (SF-36) questionnaire, applied Activities of Daily Living, Instrumental Activities of Daily Living, Subjective Global Assessment scales, Karnofsky Index, and analyzed their social conditions.Patients (126 males) had a mean age of 72.03+11.9 years, and a dialytic age of 42.6+55.6 months. The physical component of QoL (39.3+10.4) is more compromised than the mental one that is 48.5+8.6 (0–100 scale). Dependence (p<0.001), malnutrition (p=0.001) and disability (p=0.005) had a negative role on many domains of SF-36. Linear regression analysis excluded comorbidities, even significant at an univariate analysis (data adjusted for gender, age and age in dialysis).Living with family (p=0.002), good economic conditions (p=0.01), and, above all, social relationships (p<0.001) were significantly related with a better QoL (test ANOVA).Constant screening of patients, nutritional and functional rehabilitation, prevention of social isolation through social and health services are indispensable to guarantee a satisfactory QoL.

Sleep duration has progressively fallen over the last 100 years while obesity has increased in the past 30 years. Several studies have reported an association between chronic sleep deprivation and long-term weight gain. Increased energy intake due to sleep loss has been listed as the main mechanism. The consequences of chronic sleep deprivation on energy expenditure have not been fully explored. Sleep, body weight, mood and behavior are subjected to circannual changes. However, in our modern environment seasonal changes in light and ambient temperature are attenuated. Seasonality, defined as cyclic changes in mood and behavior, is a stable personality trait with a strong genetic component. We hypothesize that the attenuation in seasonal changes in the environment may produce negative consequences, especially in individuals more predisposed to seasonality, such as women. Seasonal affective disorder, a condition more common in women and characterized by depressed mood, hypersomnia, weight gain, and carbohydrate craving during the winter, represents an extreme example of seasonality. One of the postulated functions of sleep is energy preservation. Hibernation, a phenomenon characterized by decreased energy expenditure and changes in the state of arousal, may offer useful insight into the mechanisms behind energy preservation during sleep. The goals of this article are to: a) consider the contribution of changes in energy expenditure to the weight gain due to sleep loss; b) review the phenomena of seasonality, hibernation, and their neuroendocrine mechanisms as they relate to sleep, energy expenditure, and body weight regulation.

Summary:The linear viscoelastic response of polymers from a nematogenic azobenzene methacrylate and its copolymers with nonmesogenic methyl methacrylate was studied. These samples showed thermorheological simplicity in the whole investigated temperature range, even across the nematic‐isotropic transition. The temperature dependence of the zero‐shear viscosity confirmed a thermorheologically simple behavior, which allowed interpretation of η(T) in the framework of free‐volume theory. The way the relaxation mechanisms tended to their asymptotic behavior was described in terms of fragility parameters, and a comparison of fragilities of the samples was carried out. The analysis of fragility and temperature dependence of viscosity provided better understanding of the way the architecture of these nematic polymers influences free‐volume quantities and determines relaxation mechanisms.

Asymmetric antiferroelectric liquid crystal displays (AAFLCD) are attractive since they show a very well defined off state and fast switching time. Moreover, they can be driven by a simple biasless DC compensated waveform. The electrooptical response of an AAFLCD allows for new addressing modes, including quasi-static intermediate greyscales maintained without applying a field and passively addressed multiplexed high-frequency displays and spatial light modulators. A new kind of asymmetric cells have been obtained by using fluorinated block copolymer (FBC) alignment, which enhances surface segregation and provides a low energy surface. In this work we combine FBC alignment with antiferroelectric liquid crystal mixtures containing strongly electronegative fluorinated components. Threshold voltages for the antiferroelectric-ferroelectric phase transition as low as 3 volts are observed. We report the time evolution of the shift of the electro-optical response.

In somatostatinoma, a rare malignant somatostatin (SST)-secreting neoplasia, tumour regression is rarely observed, implying the need for novel antiproliferative strategies. Here, we characterized a long-term culture (SST-secreting cancer (SS-C cells)) established from a human somatostatinoma. High concentrations of SST and chromogranin A were released by SS-C cells and SST release was stimulated by depolarizing stimuli and inhibited by the SST analogue, octreotide. SS-C cells expressed mRNA for SST receptor (SSTR) subtypes 1, 2 and 4, being also able to bind native SST. Moreover, SS-C cells were positively stained with an antibody to SSTR2. SS-C cells also expressed interferon-γ (IFN-γ) receptor mRNA and measurable telomerase activity. Our findings indicate that in vitro exposure of SS-C cells to native SST-28, to octreotide, to IFN-γ, or to 3'-azido-3'deoxythymidine (AZT), a telomerase inhibitor, results in inhibition of SS-C cell proliferation. Concomitant with growth inhibition, apoptosis was detected in SST-, octreotide-, IFN-γ- or AZT-treated SS-C cell cultures. Taken together our results characterized native SST, SST analogues, IFN-γ and a telomerase inhibitor as growth-inhibiting and proapoptotic stimuli in cultured human somatostatinoma cells. Based on these findings, the potential of SST analogues, IFN-γ and AZT, alone or in combination, should be further explored in the medical treatment of somatostatinoma.

In somatostatinoma, a rare malignant somatostatin (SST)-secreting neoplasia, tumour regression is rarely observed, implying the need for novel antiproliferative strategies. Here, we characterized a long-term culture (SST-secreting cancer (SS-C cells)) established from a human somatostatinoma. High concentrations of SST and chromogranin A were released by SS-C cells and SST release was stimulated by depolarizing stimuli and inhibited by the SST analogue, octreotide. SS-C cells expressed mRNA for SST receptor (SSTR) subtypes 1, 2 and 4, being also able to bind native SST. Moreover, SS-C cells were positively stained with an antibody to SSTR2. SS-C cells also expressed interferon-γ (IFN-γ) receptor mRNA and measurable telomerase activity. Our findings indicate that in vitroexposure of SS-C cells to native SST-28, to octreotide, to IFN-γ, or to 3′-azido-3′deoxythymidine (AZT), a telomerase inhibitor, results in inhibition of SS-C cell proliferation. Concomitant with growth inhibition, apoptosis was detected in SST-, octreotide-, IFN-γ- or AZT-treated SS-C cell cultures. Taken together our results characterized native SST, SST analogues, IFN-γ and a telomerase inhibitor as growth-inhibiting and proapoptotic stimuli in cultured human somatostatinoma cells. Based on these findings, the potential of SST analogues, IFN-γ and AZT, alone or in combination, should be further explored in the medical treatment of somatostatinoma.

Systematic studies on symmetric twin molecules composed of two bent-core mesogenic units are reported for the first time. It is shown that the formation of mesophases mainly depends on the chemical structure of the spacer. A sufficiently flexible spacer containing dimethylsiloxane units allows a decoupling of the mesogenic moieties; the related compounds exhibit a ferroelectric SmCP phase proved by electro-optical measurements. On the basis of X-ray data, a plausible structure model is presented. The connection of two bent-core mesogenic units by means of a tetraethylene glycol spacer results in dimers, which are able to form columnar phases. For twins containing a simple hydrocarbon chain as spacer, in most cases liquid-crystalline behavior could not be detected. These general tendencies remain valid if the bent-core unit is changed, e.g., by increasing the number of aromatic rings, by lateral substitution, and by inversion of the direction of one of the connecting groups between the aromatic rings, respectively. The mesophase behavior of the new dimers is compared with that of the corresponding single-unit compounds as well as a related dendrimer and a polymer. It is of interest that the antiferroelectric switching behavior found for the nonchiral “monomeric” compounds is changed to a ferroelectric behavior for the dimeric compounds.

A series of novel low molecular weight organosiloxane compounds have been investigated using a number of techniques such as: texture, birefringence measurements and dielectric spectroscopy. Some materials under investigation are shown to have a direct transition to de Vries SmA* phase on cooling from the isotropic phase, whereas the others show first a transition from isotropic to orthogonal SmA*, followed by a transition from orthogonal SmA* to de Vries SmA* phase.

Surface-grafted styrene-based homopolymer and diblock copolymer brushes bearing semifluorinated alkyl side groups were synthesized by nitroxide-mediated controlled radical polymerization on planar silicon oxide surfaces. The polymer brushes were characterized by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and time-dependent water contact angle measurements. Angle-resolved XPS studies and water contact angle measurements showed that, in the case of the diblock copolymer brushes, the second block to be added was always exposed at the polymer−air interface regardless of its surface energy. Values of z*/Rg were estimated based on the radius of gyration, Rg, of the grafted homopolymer or block copolymer chains for the grafted brushes and thickness of the brush, z*. The fact that z*/Rg > 1 suggests that all these brushes are stretched. These results support the idea that after grafting the first block onto the surface the nitroxide-end capped polymer chains were able to polymerize the second block in a “living” fashion and the stretched brush so formed was dense enough that the outermost block in all cases completely covers the surface. NEXAFS analysis showed a relationship between the surface orientation of the fluorinated side chains and brush thickness with thicker brushes having more oriented side chains. Time-dependent water contact angle measurements revealed that the orientation of the side chains of the brush improved the surface stability toward reconstruction upon prolonged exposure to water.

The surface structure and surface energy properties of fluorinated 2‐vinylcyclopropane copolymers were investigated. The copolymers were prepared by free radical ring opening polymerization of fluorinated 1 and non‐fluorinated 2 2‐vinylcyclopropanes. NEXAFS experiments proved that the film surface was ordered with the fluorinated side groups possessing a relatively high orientational order. Contact angle measurements with different interrogating liquids permitted the polymer surface tension to be estimated. These surfaces showed both hydrophobic and oleophobic character, consistent with a low surface energy.

Two new block copolymers containing dimethylsiloxane and semifluorinated styrene blocks (BSF6 and BSF8) were prepared using a polysiloxane azo-macroinitiator and corresponding semifluorinated styrene monomers StyF6 and StyF8. The thermal properties of the block copolymers were investigated by DSC, which showed the formation of a thermotropic mesophase in BSF8. This was attributed to the self-assembly of the semifluorinated side groups in microphase-separated domains of the incompatible polymer blocks. Coatings with 300 nm thicknesses had a root-mean-square roughness of 10 nm by atomic force microscopy. Using water and alcohols, wetting behavior was studied along with a model poly(dimethylsiloxane) (PDMS) network. High advancing (θadv = 122°) and receding (θrec = 82°) water contact angles were observed for BSF8. Using 2-propanol, BSF8 displayed oleophobicity (θadv = 64° and θrec = 45°) while a reference PDMS coating was completely wetted (θadv = θrec = 0°). Utilizing θadv for a series of alcohols, a fit to a modified equation of state gave a low value for BSF8 surface tension (γSV = 10.5 mN/m). Both the wetting behavior of BSF8 and surface dynamics associated with wetting are consistent with the presence of a well-ordered, liquid crystalline fluorocarbon surface domain. In contrast, BSF6 surfaces are swollen by alcohols and display a cycle-dependent wetting behavior in water. BSF6 surfaces are thus labile to surface reorganization and/or solvent adsorption.

Due to its liver toxicity, the medicinal use of germander (Teucrium chamaedrys L.) was banned in some countries. Nevertheless, alcoholic extracts are still permitted as flavour ingredients since they are fundamental in providing a bitter aromatic taste. Teucrin A represents the substance of major concern regarding the potential toxicity of germander. Hence, teucrin A represents the best analytical and toxicological marker of alcoholic extracts of T. chamaedrys. A sensitive high-performance liquid chromatography method to detect teucrin A in beverages is reported. Teucrin A was prepared by isolation from the plant extract using column chromatography and crystallization. The identity and purity (99%) were established by melting point, nuclear magnetic resonance and liquid chromatography-mass spectrometry. The high-performance liquid chromatography procedure was validated and its intra- and interday performance was established (relative standard deviation ≤13% and error ≤10%). In-house validation was carried out by analysing samples of beverages not containing T. chamaedrys spiked with a range of concentrations of teucrin A. The limit of detection was 0.1 ppm and the limit of quantification was 0.3 ppm. Teucrin A accounted for about 70% of the neo-clerodane diterpenoids found in the total extract of a specimen of T. chamaedrys. The content (± standard deviation) in 18 batches of different geographical origin was 2338 ± 740 ppm, per cent coefficient of variation = 32, minimum-maximum = 999-3445 ppm. The mean level of teucrin A in 10 bottles of the same brand was 6.1 ± 0.8 ppm, per cent coefficient of variation = 12. In 10 different brands found on the Italian market, the content of teucrin A ranged from not detectable to 10 ppm.

Cholesterol homoeostasis is the result of the fine tuning between intake and disposal of this molecule. High levels of cholesterol in the blood are detrimental as they may lead to excessive accumulation in vessel walls, a condition predisposing to the development of atherosclerotic lesions. Cholesterol is removed from the vessel wall and transported to the liver through a process called reverse cholesterol transport. Nuclear receptors are among the most important transcription factors regulating genes involved in different steps of reverse cholesterol transport. Here, we discuss the role of the nuclear receptors LXR (liver X receptor) and HNF-4α (hepatocyte nuclear factor-4α) in different steps of reverse cholesterol transport. LXR controls the transcription of crucial genes in cholesterol efflux from macrophages and its transport to the liver, such as ABCA1 (ATP binding cassette A1), CYP27A1 (sterol 27-hydroxylase), CLA-1 (scavenger receptor type B1) and apolipoprotein E. Some oxysterols present in oxidized low-density lipoproteins and proinflammatory cytokines modulate the activity of LXR by antagonizing the effect of activators of this receptor, thus contributing to cholesterol accumulation in macrophages. Bile acid synthesis, which represents the final step of reverse cholesterol transport, is transcriptionally regulated by several nuclear receptors at the level of the liver-specific cytochrome P450 cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme of this metabolic pathway. Bile acids returning to the liver through the enterohepatic circulation down-regulate CYP7A1 transcription via the bile acid sensors farnesoid X receptor and HNF-4α. Based on this evidence, these nuclear receptors are candidate targets of new drugs for the treatment and prevention of atherosclerotic disease.

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Groundwater surveys were performed by detailed(around 300 sites) grid-analysis of water temperature, pH, redox potential, electrical conductivity, 222Rn, alkalinity and by calculating the pCO2, throughout the Ciampinoand Marinotowns in the Alban Hills quiescent volcano (Central Italy). Following several episodes of dangerous CO2exhalation from soils during the last 20 years and earlier ashistorically recorded, the work aimed at assessing the Natural Gas Hazard(NGH) including the indoor-Rn hazard. The NGH was defined as the probability of an area to become a site of poisonous peri-volcanic gas exhalations from soils to the lower atmosphere (comprising buildings). CO2was found to be a ``carrier'' for the other poisonous minor and in trace components (HsS, CH4, 222Rn, etc.). This assessment was performed by extrapolating in the aquifer CO2and 222Rn conditions, and discriminating sectors where future CO2flux in soils as well as indoor-Rn measurements have to be noted. A preliminary indoor-Rn survey was performed at about 200 sites. The highest values were found in the highest pCO2and high 222Rn values in groundwater. This indicates convection and enhanced permeability in certain sectors of the main aquifer, i.e., along the bordering faults and inside the gas-trap of the Ciampino Horst., where ``continuous gas-phase micro-macro seepage mechanism'' is invoked to explain the high peri-volcanic gases flux.

Two families of narrow polydispersity poly(styrene)-based block copolymers bearing side groups containing both a phenyl ring and a para-linked semifluorinated side group were designed to produce stable low energy surfaces. The effects of the phenyl ring on the surface and bulk structure of the materials were investigated. The semifluorinated side chains were found to self-assemble into liquid-crystalline smectic layers within the microphase domains. An unexpected enhancement of surface organization by the aromatic group was observed. The bulk morphology and the interplay between microphase separation and liquid crystalline self-assembly were examined using transmission electron microscopy and X-ray scattering. Near-edge X-ray absorption fine structure (NEXAFS) studies were used to probe the surface coverage of the fluorinated segments. NEXAFS also allowed the determination of the orientation parameters (SC-F and Sπ*) of the C−F bond and phenyl ring of the semifluorinated side groups at the surface. On the basis of these data, the orientational coupling between the −CF2− helix and the aromatic ring was found to depend on the length of the fluorocarbon substituent.

AbstractThe large extracellular loop of human CD81, a tetraspanin mediating hepatitis C virus envelope protein E2 binding to human cells, has been crystallized in a hexagonal form. The threedimensional structure, solved and refined at 2.6 å resolution (Rfactor = 22.8%), shows that the protein adopts a dimeric assembly, based on an association interface built up by tetraspaninconserved residues. Structural comparisons with the tertiary structure of human CD81 large extracellular loop, previously determined in a different crystal form, show marked conformational fluctuations in the molecular regions thought to be involved in binding to the viral protein, suggesting rules for recognition and assembly within the tetraspan web.

We employ density functional and quantum Monte Carlo calculations to show that significant changes occur in the optical gap of fully hydrogenated nanoclusters when the surface contains impurity passivants such as atomic oxygen. Our results show that quantum confinement is only one mechanism responsible for visible photoluminescence in silicon nanoclusters and that the specific surface chemistry must be taken into account in order to interpret experimental results. In the case of oxygen, the gap reduction computed as a function of the nanocluster size provides a consistent interpretation of several recent experiments. Furthermore, we predict that other double bonded groups also significantly affect the optical gap while single bonded groups have a minimal influence.

A chiral copolysiloxane was synthesized that exhibited an N * phase in the 9-41 ° C temperature range. A linear electro-optical response with the applied electric field was detected in the N * phase due to the electroclinic effect. At high electric fields, the linearity of the response was strongly affected by dielectric coupling. It was found, however, that the influence of dielectric coupling on the electro-optical response became zero at a particular temperature ( T =37 ° C), which was attributed to a sign reversal of the dielectric anisotropy.

We synthesized a new chiral liquid crystalline monomer and the corresponding polysiloxane and investigated their electro-optic responses. The monomer exhibited a rich phase sequence, whereas the tendency to polymorphism was strongly reduced in the polymer. The apparent molecular tilt θ pp in the chiral smectic C phase of the monomer differed substantially from that of the polymer. Whereas θ pp of the monomer reached the maximum value of 28°, the one of the polymer was nearly 45° independent of temperature over a wide range of about 30 °C.

In this paper we describe our recent work on optical effects due to photoinduced molecular reorientation in a side chain liquid crystalline polymer, namely azo-polymethacrylate (PMA4). We have studied several kinds of optical effects on space scales ranging from the nanoscopic to macroscopic. In particular, we have built a computer controlled microscope-based apparatus to study photoinduced effects down to the micron scale in thin and ultrathin (Langmuir Blodgett) films of our material. Furthermore we measured the morphology and the photoinduced surface deformation by Atomic Force Microscopy in the submicron scale.

Heterogeneities induced in a nematic polymethacrylate by thermal annealing in the isotropic phase were investigated by studying the dynamics of the cholestane spin probe dissolved in the host matrix by electron spin resonance. The molecular site distribution was well described by a two δ-like distribution function. The temperature dependences of the dynamics of the slow and fast components were fully characterized in going from the isotropic state to the glassy state through the nematic phase. It was found that the behaviors of the spinning correlation times with temperature in the isotropic and nematic regions were well represented by the Vogel−Fulcher law. By comparing the temperature dependence of the probe dynamics with the α relaxation process of the polymer, we estimated the cooperativity degrees in the dynamics of the molecular probe in the different sites. The relative populations of the slow and fast sites were determined over the whole temperature range investigated. It was shown that such population was sensitive to conformational change of the polymer backbone.

The synthesis, thermal behavior, and bulk microstructure of fluorinated new liquid-crystalline polyacrylates containing spaced fluoroalkylphenyl units in the side chains were studied. While in polyacrylates poly(1) and poly(2) there was a 4-(perfluorooctylethoxy)phenyl benzoate unit, i.e., a two-phenyl mesogenic core, poly(3) contained a 4-perfluorooctylethyl benzoate, i.e., a one-phenyl aromatic core that per se would not be able to promote a thermotropic behavior. X-ray diffraction studies allowed identification of the mesophases (hexatic smectic, disordered smectic, nematic) and study of the evolution of their structures and lattice parameters with temperature. It was found that each polymer presented a rich mesophase polymorphism, including the rather unusual smectic F2- (or I2-) to-nematic transition in poly(3). The electron density profiles along the smectic layer normal were drawn and provided a deeper insight into the packing of the side chains in tilted double layer structures. The strong mesogenic character of the polymers was attributed to the presence of the fluorinated tail on the aromatic core owing to its capability of adopting a rigid-rodlike conformation. A phase separation occurring at the molecular level of the different incompatible aliphatic−aromatic−fluoroaliphatic sections of the polymer repeat unit should efficiently cooperate to the onset of thermotropic mesomorphism.

Bile acids regulate the cholesterol 7alpha-hydroxylase gene (CYP7A1), which encodes the rate-limiting enzyme in the classical pathway of bile acid synthesis. Here we report a novel mechanism whereby bile acid feedback regulates CYP7A1 transcription through the nuclear receptor hepatocyte nuclear factor-4 (HNF-4), which binds to the bile acid response element (BARE) at nt -149/-118 relative to the transcription start site. Using transient transfection assays of HepG2 cells with Gal4-HNF-4 fusion proteins, we show that chenodeoxycholic acid (CDCA) dampened the transactivation potential of HNF-4. Overexpression of a constitutive active form of MEKK1, an upstream mitogen-activated protein kinase (MAPK) module triggered by stress signals, strongly repressed the promoter activity of CYP7A1 via the consensus sequence for HNF-4 embedded in the BARE. Similarly, MEKK1 inhibited the activity of HNF-4 in the Gal4-based assay. The involvement of the MEKK1-dependent pathway in the bile acid-mediated repression of CYP7A1 was confirmed by co-transfecting a dominant negative form of the stress-activated protein kinase kinase, SEK, which abolished the effect of CDCA upon CYP7A1 transcription. Treatment of transfected HepG2 cells with tumor necrosis factor alpha (TNF-alpha), an activator of the MEKK1 pathway, led to the repression of CYP7A1 via the HNF-4 site in the BARE. TNF-alpha also inhibited the transactivation potential of HNF-4. Collectively, our results demonstrate for the first time that HNF-4, in combination with a MAPK signaling pathway, acts as a bile acid sensor in the liver. Furthermore, the effects of CDCA and TNF-alpha converge to HNF-4, which binds to the BARE of CYP7A1, suggesting a link between the cascades elicited by bile acids and pro-inflammatory stimuli in the liver.