Crystalline misfit-angle implications for solid sliding

For the contact of two finite portions of interacting rigid crystalline surfaces, we compute the pinning energy barrier dependency on the misfit angle and contact area. This simple model allows us to investigate a broad contact-size and angular range, thus obtaining the statistical properties of the energy barriers opposing sliding for a single asperity. These data are used to generate the distribution of static frictional thresholds for the contact of polycrystals, as in dry or even lubricated friction. This distribution is used as the input of a master equation to predict the sliding properties of macroscopic contacts.     

Measurement of ultraweak transitions in the visible region of molecular oxygen

A highly sensitive cavity-enhanced frequency modulation spectroscopy technique has been used to measure ultraweak transitions in molecular oxygen that had not previously been characterized. The self-broadened half-width and line intensity of the measured transitions are reported. We include 12 high J transitions in the band of ¹⁶O₂ (the so-called A band), 59 transitions in the hot band of ¹⁶O₂, and 17 high J transitions in the band of ¹⁶O¹⁸O. Our measurements of line positions of the ¹⁶O¹⁸O transitions are used to determine improved molecular constants for the excited state of ¹⁶O¹⁸O.     

The use of vibrational spectroscopy to study the pathogenesis multiple sclerosis and other neurological conditions

Spectroscopy techniques are valuable tools in biomedical research and have been used extensively in the study of disease. However, neurological conditions such as multiple sclerosis (MS) have received little attention and the available spectroscopy studies are limited, both in overall numbers of patients studied and the disease samples considered. MS is a complex immune-mediated disease, with variable clinical courses and limited therapeutic options. This review aims to summarize current literature in the area, demonstrating how spectroscopy techniques can provide valuable information to inform and advance research into the most common neurological condition affecting young adults.     

Interests diffusion on a semantic multiplex

Exploiting the information about members of a Social Network (SN) represents one of the most attractive and dwelling subjects for both academic and applied scientists. The community of Complexity Science and especially those researchers working on multiplex social systems are devoting increasing efforts to outline general laws, models, and theories, to the purpose of predicting emergent phenomena in SN’s (e.g. success of a product). On the other side the semantic web community aims at engineering a new generation of advanced services tailored to specific people needs. This implies defining constructs, models and methods for handling the semantic layer of SNs. We combined models and techniques from both the former fields to provide a hybrid approach to understand a basic (yet complex) phenomenon: the propagation of individual interests along the social networks. Since information may move along different social networks, one should take into account a multiplex structure. Therefore we introduced the notion of “Semantic Multiplex”. In this paper we analyse two different semantic social networks represented by authors publishing in the Computer Science and those in the American Physical Society Journals. The comparison allows to outline common and specific features.     

Glycoconjugated Metallohelices have Improved Nuclear Delivery and Suppress Tumour Growth In Vivo

Monosaccharides are added to the hydrophilic face of a self‐assembled asymmetric Fe^II metallohelix, using CuAAC chemistry. The sixteen resulting architectures are water‐stable and optically pure, and exhibit improved antiproliferative selectivity against colon cancer cells (HCT116 p53^+/+) with respect to the non‐cancerous ARPE‐19 cell line. While the most selective compound is a glucose‐appended enantiomer, its cellular entry is not mainly glucose transporter‐mediated. Glucose conjugation nevertheless increases nuclear delivery ca 2.5‐fold, and a non‐destructive interaction with DNA is indicated. Addition of the glucose units affects the binding orientation of the metallohelix to naked DNA, but does not substantially alter the overall affinity. In a mouse model, the glucose conjugated compound was far better tolerated, and tumour growth delays for the parent compound (2.6 d) were improved to 4.3 d; performance as good as cisplatin but with the advantage of no weight loss in the subjects.     

The Influence of Different Bleaching Protocols on Dentinal Enzymatic Activity: An In Vitro Study

This study aimed to investigate matrix metalloproteinase (MMP) activity in human dentin using in-situ and gelatin zymography, after at-home and in-office bleaching, related to their clinical exposure times. Dentin specimens (n = 5) were treated with 35% hydrogen peroxide (50 min per session/4 sessions), 10% carbamide peroxide (180 min/21 sessions), or no treatment. All were subjected to in-situ zymography. Dentin slices were, subsequently, obtained, covered with fluorescein-conjugated gelatin, and examined with confocal laser-scanning microscopy. The fluorescence intensity was quantified and statistically analyzed using one-way ANOVA and Bonferroni tests (α = 0.05). Furthermore, gelatin zymography was performed on protein extracts obtained from dentin powder (N = 8 teeth), treated with hydrogen peroxide or carbamide peroxide, with different exposure times (10/50 min for hydrogen peroxide; 252/1260 min for carbamide peroxide). The results of the in-situ zymography showed no statistical differences between the bleached specimens and the control group, with a medium level of gelatinolytic activity expressed in the dentin tubules. The results of gelatin zymography showed an increased expression of pro-MMP-9 in carbamide peroxide groups. The expression of pro-MMP-2 decreased in all the experimental groups. The bleaching treatments performed on the enamel of sound teeth do not influence dentinal enzymatic activity. However, when unprotected dentin tissue is bleached, matrix metalloproteinases are more expressed, particularly when carbamide peroxide is used, proportional to the exposure time.     

On-Surface Synthesis and Characterization of Acene-Based Nanoribbons Incorporating Four-Membered Rings

A bottom up method for the synthesis of unique tetracene-based nanoribbons, which incorporate cyclobutadiene moieties as linkers between the acene segments, is reported. These structures were achieved through the formal [2+2] cycloaddition reaction of ortho-functionalized tetracene precursor monomers. The formation mechanism and the electronic and magnetic properties of these nanoribbons were comprehensively studied by means of a multitechnique approach. Ultra-high vacuum scanning tunneling microscopy showed the occurrence of metal-coordinated nanostructures at room temperature and their evolution into nanoribbons through formal [2+2] cycloaddition at 475 K. Frequency-shift non-contact atomic force microscopy images clearly proved the presence of bridging cyclobutadiene moieties upon covalent coupling of activated tetracene molecules. Insight into the electronic and vibrational properties of the so-formed ribbons was obtained by scanning tunneling microscopy, Raman spectroscopy, and theoretical calculations. Magnetic properties were addressed from a computational point of view, allowing us to propose promising candidates to magnetic acene-based ribbons incorporating four-membered rings. The reported findings will increase the understanding and availability of new graphene-based nanoribbons with high potential in future spintronics.     

A lower bound for systems with double characteristics

We give necessary and sufficient conditions for a lower bound with a gain of 3/2 derivatives (the so-called Weak-Hörmander inequality) for a class of systems with double characteristics.     

Intriguing sets in partial quadrangles

The point‐line geometry known as a partial quadrangle (introduced by Cameron in 1975) has the property that for every point/line non‐incident pair (P, ?), there is at most one line through P concurrent with ?. So in particular, the well‐studied objects known as generalized quadrangles are each partial quadrangles. An intriguing set of a generalized quadrangle is a set of points which induces an equitable partition of size two of the underlying strongly regular graph. We extend the theory of intriguing sets of generalized quadrangles by Bamberg, Law and Penttila to partial quadrangles, which gives insight into the structure of hemisystems and other intriguing sets of generalized quadrangles. © 2010 Wiley Periodicals, Inc. J Combin Designs 19:217‐245, 2011     

On the transfer matrix of a MIMO system

We develop a deterministic ab initio model for the input–output relationship of a multiple‐input multiple‐output (MIMO) wireless channel, starting from the Maxwell equations combined with Ohm's law. The main technical tools are scattering and geometric perturbation theories. The derived relationship can lead us to a deep understanding of how the propagation conditions and the coupling effects between the elements of multiple‐element arrays affect the properties of an MIMO channel, e.g. its capacity and its number of degrees of freedom. Copyright © 2011 John Wiley & Sons, Ltd.