Comparison of confinement characters between porous silicon and silicon nanowires

Confinement character and its effects on photoluminescence (PL) properties are theoretically investigated and compared between porous silicon (p-Si) and silicon nanowires (Si-NWs). The method is based on the application of the tight-binding technique using the minimal sp³-basis set, including the second-nearest-neighbor interactions. The results show that the quantum confinement (QC) is not entirely controlled by the porosity, rather it is mainly affected by the average distance between pores (d). The p-Si is found to exhibit weaker confinement character than Si-NWs. The confinement energy of charge carriers decays against d exponentially for p-Si and via a power-law for Si-NWs. This latter type of QC is much stronger and is somewhat similar to the case of a single particle in a quantum box. The excellent fit to the PL data demonstrates that the experimental samples of p-Si do exhibit strong QC character and thus reveals the possibility of silicon clustering into nano-crystals and/or nanowires. Furthermore, the results show that the passivation of the surface dangling bonds by the hydrogen atoms plays an essential role in preventing the appearance of gap states and consequently enhances the optical qualities of the produced structures. The oscillator strength (OS) is found to increase exponentially with energy in Si-NWs confirming the strong confinement character of carriers. Our theoretical findings suggest the existence of Si nanocrystals (Si-NCs) of sizes 1-3 nm and/or Si-NWs of cross-sectional sizes in the 1-3 nm range inside the experimental p-Si samples. The experimentally-observed strong photoluminescence from p-Si should be in favor of an exhibition of 3D-confinement character. The favorable comparison of our theoretical results with the experimental data consolidates our above claims.     

Holographic watermarking for authentication of cut images

A watermarking technique, with a Computer Generated Hologram (CGH) coding system of the mark, is introduced and tested. The CGH watermarking can be used to authenticate parts of the original image. The hologram of the mark is embedded in the spatial domain by a blind additive embedding technique. The use of holography allows authenticating cuts of the original image, is the major novelty of this paper. The proposed methodology is characterized as an authentication technique, since it does not rely on the original image to decide whether the watermarked image has been altered or not and at the same time it is able to detect and localize any possible malicious change. Asymmetric cryptography is used to hide the hash information in an unambiguous way (non-repudiation property).     

Molecular Pom Poms from Self‐Assembling α,γ‐Cyclic Peptides

The hierarchical self‐assembly properties of a dimer‐forming cyclic peptide that bears a nicotinic acid moiety to form molecular pom‐pom‐like structures are described. This dimeric assembly self organizes into spherical structures that can encapsulate small organic molecules owing to its porosity and it can also facilitate metal deposition on its surface directed by the pyridine moiety.     

Determination of Flavonoids and Resveratrol in Wine by Turbulent-Flow Chromatography-LC-MS

Turbulent-flow chromatography (TFC) on-line coupled to liquid chromatography mass spectrometry (LC-MS) is used to determine flavonoids and resveratrol in different types of wines. A fully automated system was developed in which 10 mL of sample (diluted wine) was passed over a TFC column, after which the retained analytes were separated by reversed-phase LC and detected by negative ion mode atmospheric-pressure chemical ionization (APCI) MS. The method proved to be fast, non-laborious, robust and sensitive. The feasibility of the method was tested on several red, white and rose wines. Quantitation of resveratrol was possible using the standard addition procedure. Red wine showed the highest amount of resveratrol (4 mg L⁻¹), while rose and white wine contained concentrations which were about ten fold lower.

     

Isolation of tumor cells using size and deformation

The isolation and analysis of circulating tumor cells (CTCs) from blood are the subject of intense research. Although tests to detect metastasis on a molecular level are available, progress has been hampered by a lack of tumor-specific markers and predictable DNA abnormalities. The main challenge in this endeavor is the small number of available cells of interest, 1–2 per mL in whole blood. We have designed a micromachined device to fractionate whole blood using physical means to enrich for and/or isolate rare cells from peripheral circulation. It has arrays of four successively narrower channels, each consisting of a two-dimensional array of columns. Current devices have channels ranging in width from 20 to 5 μm, and in depth from 20 to 5 μm. Several optimizations resulting in the fabrication of a total of 10 derivative devices have been carried out; only two types are used in this study. Both have increasingly narrower gap widths between the columns along the flow axis with 20, 15, 10, and 5 μm spacing all on one device. The first 20 μm wide segment disperses the cell suspension and creates an evenly distributed flow over the entire device, whereas the others were designed to retain increasingly smaller cells. The channel depth is constant across the entire device, the first type was 10 μm deep and the second type is 20 μm deep. When cells from each of eight tumor cell lines were loaded into the device, all cancerous cells were isolated. In mixing experiments using human whole blood, we were able to fractionate cancer cells without interference from the blood cells. Additionally, either intact cells, or DNA, could be extracted for molecular analysis. The ultimate goal of this work is to characterize the cells on the molecular level to provide non-invasive methods to monitor patients, stage disease, and assess treatment efficacy. Furthermore, this work will use gene expression profiles to gain insights into metastasis.     

Uncovered bargaining solutions

An uncovered bargaining solution is a bargaining solution for which there exists a complete and asymmetric relation (tournament) such that, for each feasible set, the bargaining solution set coincides with the uncovered set of the tournament. We provide a characterization of a class of uncovered bargaining solutions.     

Influence of α- and γ- cyclodextrin lipophilic derivatives on curcumin-loaded SLN

Solid lipid nanoparticles (SLN) made of different triglycerides (TG) in the presence and in the absence of various modified α- and γ-cyclodextrins (CD) were prepared by the solvent injection technique. A new synthesis of lipophilic derivatives of γ- CD was developed in this work. Curcumin (CU), a natural polyphenol with antitumor, antioxidant and anti-inflammatory properties, was used as model drug. SLNs mean sizes were in the 250–800 nm range and afforded CU entrapment efficiency in the 12–85% range. The presence of CD derivatives with almost the same chain length of TG induced an improvement of nanoparticle characteristics decreasing mean size values and increasing CU entrapment efficiency. A significant reduction in CU photodegradation was noted only when the drug was vehicled in tristearin-SLN, which became less pronounced in the presence of CD-derivatives, determining a loss in photoprotection. The hydrolytic stability of curcumin was highly improved by drug loading in tristearin-SLN, and only slightly by loading it in tricaprin-SLN, and this seemed not to be influenced by the presence of CD derivatives. Skin uptake studies revealed an increase in CU skin accumulation when CU was loaded in SLN obtained with all CD derivatives, particularly with most lipophilic one.     

Well-posedness of the two-dimensional nonlinear Schrödinger equation with concentrated nonlinearity

We consider a two-dimensional nonlinear Schrödinger equation with concentrated nonlinearity. In both the focusing and defocusing case we prove local well-posedness, i.e., existence and uniqueness of the solution for short times, as well as energy and mass conservation. In addition, we prove that this implies global existence in the defocusing case, irrespective of the power of the nonlinearity, while in the focusing case blowing-up solutions may arise.     

An approximation scheme for the two-stage,two-dimensional knapsack problem

We present an approximation scheme for the two-dimensional version of the knapsack problem which requires packing a maximum-area set of rectangles in a unit square bin, with the further restrictions that packing must be orthogonal without rotations and done in two stages. Achieving a solution which is close to the optimum modulo a small additive constant can be done by taking wide inspiration from an existing asymptotic approximation scheme for two-stage two-dimensional bin packing. On the other hand, getting rid of the additive constant to achieve a canonical approximation scheme appears to be widely nontrivial.     

Coronary fluid mechanics in an ageing cardiovascular system

Coronary artery diseases are a leading cause of mortality and are increasingly prevalent with age. However, the large number of age-increasing co-morbidities make difficult to understand the impact of cardiovascular ageing alone on the coronary flow pattern. The present study aims to shed light on the effect of arterial and ventricular ageing on the coronary circulation, which is here studied by means of a validated mathematical model. Forward and backward pressure and flow waves are analysed, as well as their intensity. Results highlight a complex spatiotemporal coronary wave pattern, where intense waves originate from the aorta (particularly in systole) and from the deep myocardium, during both the isovolumic compression and the diastolic phase. The subendocardial viability ratio decreases with age, the total coronary flow is slightly reduced, and the left-ventricular work increases. Consequently, the left-ventricular work per unit of blood flow increases, thus limiting the cell oxygen availability abundance, and therefore increasing the risk of myocardial infarction. Our results highlight a physiological age-induced supply/demand unbalance, which can augment the risk of myocardial ischemia and can contribute to pave the way to other typical coronary pathological processes.