Reconstructing f(T) modified gravity from ECHDE and ECNADE models

We investigate alternative candidates to dark energy (DE) that can explain the current state of the Universe in the framework of the generalized teleparallel theory of gravity f(T), where T denotes the torsion scalar. To achieve this, we carry out a series of reconstructions taking into account the ordinary and entropy-corrected versions of the holographic and new agegraphic DE models. These models are used as alternatives to DE in the literature in order to describe the current state of our Universe. It is remarked that the proposed models indicate behavior akin to phantom or quintessence models. Furthermore, we also generate the parameters of the equation of state associated with entropy-corrected models and we observe a phase transition between the quintessence state and phantom state as it is shown by the recent observational data. We also investigate the stability of these models and we create the $\{r-s\}$ trajectories and compare with the ΛCDM limit. The behavior of certain physical parameters such as the speed of sound and the Statefinder diagnostic pair $\{r-s\}$ is compatible with the current observational data.     

Hydrolytic degradation and functional stability of a segmented shape memory poly(ester urethane)

In order to understand the effects of water and hydrolytic ageing on semi-crystalline poly(ester urethane) and its shape memory functionality, water immersion experiments at elevated temperature have been performed on a model substance and various parameters were monitored: change of the melting/crystallisation temperatures, substantial increase in crystallinity, temperature dependence of the water diffusion coefficient and solubility, hydrogen-bonding index and phase mixing by peak deconvolution of the FT-IR carbonyl region and day-to-day tensile and thermo-mechanical cyclic tensile tests. A rising fraction of freezable water agglomerates in the polymer was found for specimens cooled from the immersion temperature. The degradation process could be divided into three phases: an induction phase, a phase of continuous degradation and a phase of accelerated degradation. Shape recovery remains fairly constant during phase one and decreases slowly during phase two. The increase in crystallinity in phase two is accompanied by an increase in shape fixing ability.     

Factors influencing the 18O/16O-ratio in meat juices

With respect to the question of whether the 18O/16O-ratio of meat water could be used for meat origin analysis, factors influencing its delta18O-value have been examined. The 18O/16O-ratio of meat water differs geographically, similar to known differences in precipitation and ground water. In Great Britain higher enrichments in 18O were found in southern samples and in Germany in northern samples. However, it was not possible to distinguish between British and German beef: their 18O/16O-ratios overlapped. British bovine samples the variation range of delta18O-values was 2.8 per thousand; in porcine samples it was 2.0 per thousand. British meat liquids from beef were enriched in 18O by 1.3 +/- 0.3 per thousand compared with pork. In porcine samples of litter mates with identical breeding and age at slaughter, the range in the delta18O-values among individuals was 2.4 per thousand. Experiments revealed significant influences of the meat's storage and handling conditions on the 18O/16O-ratio. After 10 h at 21.5 or 18.5 degrees C the delta18O-value increased by 0.4 or 0.3 per thousand per h, respectively, in samples (50 g) of chopped meat. The observed magnitude of changes might compensate for the geographical and seasonal differences. A precise origin assignment of the affected specimen on the base of delta18O-values of meat water is hence bound to be impossible.     

Magnetic resonance imaging of cortical bone with ultrashort TE pulse sequences

PurposeNormal adult cortical bone has a very short T₂ and characteristically produces no signal with pulse sequence echo times (TEs) routinely used in clinical practice. We wished to determine whether it was possible to use ultrashort TE (UTE) pulse sequences to detect signal from cortical bone in human subjects and use this signal to characterise this tissue.Subjects and MethodsSeven volunteers and 10 patients were examined using ultrashort TE pulse sequences (TE=0.07 or 0.08 ms). Short and long inversion as well as fat suppression pulses were used as preparation pulses. Later echo images were also obtained as well as difference images produced by subtracting a later echo image from a first echo image. Saturation pulses were used for T₁ measurement and sequences with progressively increasing TEs for T₂* measurement. Intravenous gadodiamide was administered to four subjects.ResultsSignal in cortical bone was detected with UTE sequences in children, normal adults and patients. This signal was usually made more obvious by subtracting a later echo image from the first provided that the signal-to-noise ratio was sufficiently high.Normal mean adult T₁s ranged from 140 to 260 ms, and mean T₂*s ranged from 0.42 to 0.50 ms. T₁ increased significantly with age (P<.01).Increased signal was observed after contrast enhancement in the normal volunteer and the three patients to whom it was administered.Reduction in signal from short T₂ components was seen in acute fractures, and increase in signal in these components was seen with new bone formation after fracture malunion. In a case of osteoporosis, bone cross-sectional area and signal level appeared reduced.ConclusionSignal can be detected from normal and abnormal cortical bone with UTE pulse sequences, and this can be used to measure its T₁ and T₂* as well as observe contrast enhancement. Difference images are of value in increasing the conspicuity of cortical bone and observing abnormalities in disease.     

Rogiolol Acetate: A Novel β-Chamigrene-Type Sesquiterpene Isolated from a Marine Sponge

The marine sponge Spongia zimocca SCHMIDT , 1862, collected in front of the torrent II Rogiolo, south of Livorno, contains the sesquiterpene rogiolol acetate (= (+)-(2R,3S,6R,8R,9R)-2,8-dibromo-9-chloro-1,1,9-trimethyl-5-methylidenespiro[5.5]undec-3-yl acetate; (+)- 3a ), which represents the first chamigrane isolated from a sponge. Although compounds of this class are common in red seaweeds of the genus Laurencia, and our sponge actually contains 9-bromochamigrene and a variety of other metabolites of nearby growing Laurencia sp., (+)- 3a is unique to our sponge.     

Examination of Pt(111)/Ru and Pt(111)/Os surfaces: STM imaging and methanol oxidation activity

Ruthenium and osmium were deposited in submonolayer amounts on Pt(111) single crystal surfaces using the previously reported ‘spontaneous deposition’ procedure [Chrzanowski et al., Langmuir, 13 (1997) 5974]. Such surfaces were first explored using ex situ scanning tunneling microscopy (STM) to image the deposition characteristics of ruthenium and osmium islands on Pt(111). It was found that, using the spontaneous deposition procedure, a maximum coverage of 0.20 ML ruthenium is formed on the surface after 120 s of exposure to a RuCl₃ solution in 0.1 M HClO₄. A homogeneous deposition on the Pt(111) surface was found, with no observed preferential deposition on step edges or surface defect sites. In contrast, in the spontaneous deposition of osmium, osmium clusters form preferentially at, though not limited to, surface defect sites and step edges. Osmium island deposition occurs at a greater rate than ruthenium on Pt(111), and possible explanations are presented. Methanol activity on the Pt(111)/Ru and Pt(111)/Os surfaces is also studied, using the coverage values determined to yield the highest activity for methanol electro-oxidation (0.20 ML coverage for Ru and 0.15 ML for Os). At potentials more negative than 0.40 V vs. RHE, the Pt(111)/Ru surface yields a higher surface activity than Pt(111)/Os. However, at potentials more positive than 0.04 V, Pt(111)/Os exhibits demonstrably higher surface activity. The relevance of this data is discussed and future avenues of interest are indicated.     

Triple-Helix-Stabilizing Effects in Collagen Model Peptides Containing PPII-Helix-Preorganized Diproline Modules

Collagen model peptides (CMPs) serve as tools for understanding stability and function of the collagen triple helix and have a potential for biomedical applications. In the past, interstrand cross-linking or conformational preconditioning of proline units through stereoelectronic effects have been utilized in the design of stabilized CMPs. To further study the effects determining collagen triple helix stability we investigated a series of CMPs containing synthetic diproline-mimicking modules (ProMs), which were preorganized in a PPII-helix-type conformation by a functionalizable intrastrand C₂ bridge. Results of CD-based denaturation studies were correlated with calculated (DFT) conformational preferences of the ProM units, revealing that the relative helix stability is mainly governed by an interplay of main-chain preorganization, ring-flip preference, adaptability, and steric effects. Triple helix integrity was proven by crystal structure analysis and binding to HSP47.