The magnetic exchange parameters and anisotropy of the quasi-two dimensional antiferromagnet NiPS3_3

Neutron inelastic scattering has been used to measure the magnetic excitations in powdered NiPS$_3$, a quasi-two dimensional antiferromagnet with spin $S = 1$ on a honeycomb lattice. The spectra show clear, dispersive magnons with a $\sim 7$ meV gap at the Brillouin zone center. The data were fitted using a Heisenberg Hamiltonian with a single-ion anisotropy assuming no magnetic exchange between the honeycomb planes. Magnetic exchange interactions up to the third intraplanar nearest-neighbour were required. The fits show robustly that NiPS$_3$ has an easy axis anisotropy with $\Delta = 0.3$ meV and that the third nearest-neighbour has a strong antiferromagnetic exchange of $J_3 = -6.90$ meV. The data can be fitted reasonably well with either $J_1 < 0$ or $J_1 > 0$, however the best quantitative agreement with high-resolution data indicate that the nearest-neighbour interaction is ferromagnetic with $J_1 = 1.9$ meV and that the second nearest-neighbour exchange is small and antiferromagnetic with $J_2 = -0.1$ meV. The dispersion has a minimum in the Brillouin zone corner that is slightly larger than that at the Brillouin zone center, indicating that the magnetic structure of NiPS$_3$ is close to being unstable.Comment: 21 pages, 7 figures, 33 reference

Robustness assessment approaches for steel framed structures under catastrophic events

The current study deals with the robustness assessment methods of steel framed buildings under catastrophic events. Two steel framed buildings, designed according to old and new seismic Italian codes, have been herein analysed, by considering the uncertainties of both the material strength and the applied loads, through two investigation methods. First, within the methodologies used for robustness assessment under seismic loads, a deterministic method, framed within the Performance Based Seismic Design (PBSD), has been applied. Later on, the robustness of studied structures under different column-removed conditions, related to different catastrophic events (blast, impact, fire and so on), has been assessed by means of two forcebased analysis techniques (a literature approach and a more advanced procedure) in order to estimate their resistance against progressive collapse. The application of the two methods has allowed to calculate the robustness index of examined structures, by taking into account the influence of both the catenary effect phenomenon and different beam-to-column joints, with the final aim to show their behavioural difference in terms of robustness

Thermal stability and aggregation of sulfolobus solfataricus b-glycosidase are dependent upon the N-e-methylation of specific lysyl residues: critical role of in vivo post-translational modifications.

Methylation in vivo is a post-translational modification observed in several organisms belonging to eucarya, bacteria, and archaea. Although important implications of this modification have been demonstrated in several eucaryotes, its biological role in hyperthermophilic archaea is far from being understood. The aim of this work is to clarify some effects of methylation on the properties of β-glycosidase from Sulfolobus solfataricus, by a structural comparison between the native, methylated protein and its unmethylated counterpart, recombinantly expressed in Escherichia coli. Analysis by Fourier transform infrared spectroscopy indicated similar secondary structure contents for the two forms of the protein. However, the study of temperature perturbation by Fourier transform infrared spectroscopy and turbidimetry evidenced denaturation and aggregation events more pronounced in recombinant than in native β-glycosidase. Red Nile fluorescence analysis revealed significant differences of surface hydrophobicity between the two forms of the protein. Unlike the native enzyme, which dissociated into SDS-resistant dimers upon exposure to the detergent, the recombinant enzyme partially dissociated into monomers. By electrospray mapping, the methylation sites of the native protein were identified. A computational analysis of β-glycosidase three-dimensional structure and comparisons with other proteins from S. solfataricus revealed analogies in the localization of methylation sites in terms of secondary structural elements and overall topology. These observations suggest a role for the methylation of lysyl residues, located in selected domains, in the thermal stabilization of β-glycosidase from S. solfataricu

Effectiveness comparison between carbon spring and hinged ankle-foot orthoses in crouch gait treatment of children with diplegic cerebral palsy: A randomized crossover trial

BACKGROUND: Children with cerebral palsy (CP) often present a loss of effectiveness of the plantarflexors/knee-extensors couple that leads to crouch gait. When treating a child with crouch gait by means of ankle foot orthoses, preserving or restoring push off power is a key issue.AIM: To compare carbon-fiber spring (Carbon Ankle Seven (R) [CAFO], Ottobock (R) HealthCare, Duderstadt, Germany) and hinged ankle-foot orthoses (HAFO) effectiveness in improving functionality and walking ability in children with diplegic CP and crouch gait.DESIGN: Randomized crossover trial.SETTING: Hospital center.POPULATION: Ten children with diplegic CP and crouch gait, 5 males and 5 females, aged 11 (4) years.METHODS: The gait of each child was evaluated by means of instrumental gait analysis with both CAFO and HAFO, in a randomized order and after a 4-week adaptation period. The primary outcome measure was the change in ankle power generation. As secondary outcome measures, knee joint kinematics, stride length, walking speed, Observational Gait Scale, and preferred orthosis were considered.RESULTS: The median of the energy produced in stance was superior with CAFO (+2.2 J/kg, IQR 4.7, P=0.006), and the energy absorbed inferior (-3.3 J/kg, IQR 4.3, P=0.011). No statistically significant difference was found for any other parameter. Preference of the children was equally distributed between the two orthoses.CONCLUSIONS: No evident superiority of CAFO with respect to HAFO was found in improving gait performance of children with CP and crouch gait. Nevertheless, the results suggest the possibility that CAFO permits an energy saving and reduction of the more compromising deficits.CLINICAL REHABILITATION IMPACT: The final choice of the participants indicates that CAFOs are preferred by older and heavier children, but the preference does not correlate with the performance of the orthoses during gait

Experimental and Numerical Study of Perforated Steel Plate Shear Panels

Thin perforated Steel Plate Shear (SPS) Walls are among the most common types of energy dissipating systems. The applied holes reduce the shear strength of the plate and allow to decrease the profile size of the members at the boundary of the panel when these systems are used in the typical design of structures. On the other hand, the different fracture locations of these panels are visible when considering the different perforation patterns. This paper reports on the results obtained from the experimental study under cyclic loading of the effect of different hole patterns on the seismic response of the systems and the location of the fracture. According to this, two perforated specimens by different patterns were considered. In addition, a plate without holes for a better comparison of the fracture location was chosen. The results showed that changing the pattern of the holes causes a change in the fracture location. Moreover, in perforated specimens, the amount of shear strength did not reduce suddenly after the fracture phenomenon. In the specimen which was perforated around the web plate, the pinching force was more than any other in the low cycle of the drifts. For this reason, the energy dissipation and initial stiffness were more than up to 3% drift. The experimental specimens were then simulated with a Finite Element (FE) method using the ABAQUS. Finally, a parametric FE analysis on different series of perforated panels, by changing the diameter of the holes and the plate thickness, has been carried out

FRCM retrofitting techniques for masonry walls: a literature review and some laboratory tests

The experimental characterisation of externally bonded composite materials as strengthening solutions for masonry structures, such as basalt textile reinforced mortar (BTRM) or fiber reinforced concrete (FRC), has been receiving increasing attention due to their outstanding mechanical performance. Several studies have been demonstrated the efficiency of this retrofitting solution for increasing the mechanical strength and the displacement capacity of masonry material. In this paper the state-of-art of the most relevant achievements in the experimental investigations and numerical analysis of retrofitted masonry wall have been critically reviewed. Firstly, a detailed collection of several experimental tests using different textile reinforced mortar and/or fiber reinforced mortar has been conducted. Special focus has been given to the test set-up and load configuration type adopted for experiments. Subsequently, several modelling techniques have been treated in order to detect the best approach simulating the interaction between reinforcement system and masonry ranging from macro and micro modelling, concentrated and diffused plasticity model and diverse constitutive laws. Finally, an overview of some original experimental outcomes from laboratory tests is presented. This results will play a major role in for the validation of the numerical models for the prediction of the shear strength and the ductile behavior of reinforced masonry that will be developed in a further step of this research

hedgehog pathway influence in the immune escape of tumor cells through pdl 1 modulation

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