Small Cells in Cellular Networks: Challenges of Future HetNets

Due to their low cost and easy deployment, small cells provide a viable and cost-effective way of improving the cellular coverage and capacity both for homes and enterprises, both in metropolitan and rural areas. Stimulated by their attractive features and advantages, the ongoing development and deployment of small cells by manufacturers and mobile network operators have seen a surge in recent years. Together with macro-cells, they form, what are called Heterogeneous Networks or HetNets. However, the successful rollout and operation of small cells are still facing significan issues. In this paper the need for, challenges and solutions of small cell deployments are analyzed. This analysis is conducted with respect to self-organizing features, interference coordination, energy efficiency and spectrum efficiency. The analysis is complemented with numerical results based on system simulations in Macro-only and HetNet scenarios and also on real measurements performed on an mobile operator network. Results show the clear improvement that a HetNet brings in term of user throughput and also the amunt of spectrum waste that is present in nowadays’ operator networks.     

Supercritical carbon dioxide-treated blood orange juice as a new product in the fresh fruit juice market

The work described here deals with the effectiveness of using high-pressure carbon dioxide treatment (HPCD) to stabilise freshly squeezed blood orange juice. Technical planning of a continuous high-pressure supercritical carbon dioxide pilot system, suitable for development on an industrial scale, was carried out in our lab. To determine the optimal operating conditions (temperature, pressure, and CO₂/juice ratio), three different experimental trials were carried out. The first trial was conducted at 230 bar, 36 ± 1 °C, 5.08 L/h juice flow rate, and 3.91 L/h CO₂ flow rate, corresponding to a g_CO2/g_juice ratio of 0.770. The second trial utilised the same conditions except that the operative pressure was reduced (130 bar). The third trial was carried out at 130 bar, 36 ± 1 °C, 5.08 L/h juice flow rate, 1.96 L/h CO₂ flow rate, corresponding to a 0.385 g_CO2/g_juice ratio. The effects of processing were evaluated by determining physicochemical, antioxidant, and microbiological parameters of the treated juices. In addition, once the best operative parameters had been determined, physicochemical, antioxidant, microbiological and sensory evaluation of fresh blood orange juice stabilised by HPCD treatment was carried out during refrigerated storage of juices at 4 ± 1 °C for thirty days. The results showed that HPCD treatment cannot be considered as an alternative to traditional thermal methods but as a new mild technology for producing a stabilised blood orange juice with a shelf-life of 20 days.Industrial relevanceBlood oranges are the main cultivated varieties of Citrus sinensis (L.) Osbeck in Italy. Freshly squeezed blood orange juice exert a high antiradical and antioxidant activity, due to its rich phenolic profile, but its preservation is usually assured by thermal treatment which affects its nutritional and sensory value. In this study we proposed a “milder” continuous HPCD process suitable for implementation on an industrial scale. The HPCD stabilised juice retains its physicochemical, antioxidant, and sensory properties and could be placed within a new retail framework, namely, that of fresh juices with a shelf-life of 20 days.     

Preparation of immobilized Trametes pubescens laccase on a cryogel-type polymeric carrier and application of the biocatalyst to apple juice phenolic compounds oxidation

A new biocatalyst was prepared by the immobilization of a Trametes pubescens laccase, into a wide-pore poly(vinyl alcohol) cryogel. The known enzyme was produced and purified by the previously described procedure. The resulted laccase (yield 40%) has an activity of 46.4 U mg⁻¹ and 12.51 mg mL⁻¹ protein content. The enzyme was subsequently immobilized in a functionalized macroporous cryogel beads by a covalent immobilization technique. The time dependence of the immobilization process and the enzyme loading of the carrier material (5.2 mg g⁻¹ cryogel) were determined by measuring the decrease of protein amount in the enzyme solution. In conversion experiments, a higher stability of the immobilized biocatalyst compared to the free enzyme was evidenced. Steady-state kinetic characterization of four phenols (catechol, caffeic and chlorogenic acids, and catechin) has been performed with free and immobilized laccase, the catalytic parameters being determined and compared. The effect of both laccases (free and immobilized) on the phenol content of retailed apple juice samples, having the same initial composition, was also investigated by working in batch conversion. The variation in phenolic compound content has been compared with that of an untreated apple juice sample having initially the same content of phenolic compounds. A number of advantages resulted in using the immobilized laccase for the apple juice treatment (conservation to some extent of enzyme activity, higher content of phenols preserved, easy separation of the enzyme from the apple juice, therefore avoiding the possible unhealthy effects due to the remaining protein, etc.).     

Comparison of the Frying Performance of Olive Oil and Palm Superolein

Abstract: Deep‐fat frying is an important method of food preparation in which foods are immersed in hot oil. Repeated use of frying oils is a common practice, and in the presence of atmospheric oxygen it produces various undesirable reactions in used oils. Stable frying oils usually require low linolenic acid (LnA < 3%), increased oleic acid (OA > 40%), and decreased linoleic acid (LA < 50%). The aim of this study was to establish the behavior of palm superolein (PSO) (OA 45%; LA 12.5%; LnA 0.2%) and olive oil (OO) during repeated, discontinuous deep frying of French fries. The behavior of the oils under controlled heating conditions was also studied by maintaining all of the process variables the same as those in deep frying, except that there was no food in the oil. The PSO selected to be tested in this study may represent an alternative to OO as a frying medium. Although PSO presented a faster increase in some oxidation indices, such as free fatty acid and total polar compounds, for other indicators, PSO showed better behavior than OO (less formation of C8:0 and lower peroxide value). Practical Application: The super palm olein selected for use in this study can be suggested as a suitable replacement for olive oil for frying and cooking purposes because it provides higher oxidative stability besides the beneficial effects of olive oil on human health. In fact, several studies have indicated that palm oil exhibits similar frying performance to high‐oleic oils, with the advantages of greater availability in the market and a lower price.     

Antioxidant activity of virgin olive oil phenolic compounds in a micellar system†

The antioxidant activity of two virgin olive oils, obtained from the same olive (Olea europaea sativa) batch but processed with different hammer crushing conditions, was evaluated by measuring their protective action towards linoleic acid peroxidation in a micellar system. The antioxidant efficiency (AE) of the oil phenolic fraction was higher when the olives were processed with a higher hammer crusher rotation rate. HPLC analysis demonstrated that one of the main derivatives of oleuropein, indicated as 3,4-DHPEA-EDA (the dialdehydic form of elenolic acid linked with 3,4-dihydroxyphenylethanol), is present only in the oil with higher AE. 3,4-DHPEA-EDA showed the greatest antioxidant ability among virgin olive oil phenols. Its greater efficiency in the micellar system in comparison with 3,4-dihydroxyphenylethanol (3,4-DHPEA) is related to its greater lipophilicity. It is suggested that the behaviour in the water–micellar environment is representative of that in a real system such as tomato-based sauce with added virgin olive oil. © 1999 Society of Chemical Industry     

Juice of New citrus hybrids (Citrus clementina Hort. ex Tan.×C. sinensis L. Osbeck) as a source of natural antioxidants

Fruit juices of pigmented and non-pigmented new citrus hybrids obtained by crossing clementine cv. Oroval with different cultivars of blood oranges were analysed to determine parameters related to fruit quality (total soluble solids titratable acidity, pH), and the content of ascorbic acid, total phenolics, flavanones, anthocyanins and phenolic acids. Antioxidant properties were evaluated by oxygen radical absorbance capacity (ORAC), and inhibition of induced linoleic acid peroxidation (InLAP) assays. The results of this study show that some hybrids with high antioxidant activity owing to considerable polyphenol content may be considered rich sources of phytochemicals. The OTA 9 hybrid was shown to be richest in polyphenols, suggesting that consumption of OTA 9 fruit or juice could be useful in health promotion and a disease-preventing diet. Moreover, the juice of this hybrid could be used as raw material to produce antioxidant ingredients for dietary, pharmaceutical, or cosmetic purposes.     

Functional Properties of Lactic Acid Bacteria Isolated from Romanian Fermented Vegetables

A total of 139 lactic acid bacterium (LAB) strains isolated from Romanian traditionally fermented vegetables were screened for the ability to produce exopolysaccharides and for their antagonistic activity against a set of nine LAB strains, three Bacillus strains, and four Gram-negative bacteria. Eighty-five of the tested strains showed a variable antimicrobial activity against Listeria monocytogenes ATCC 1911, 35 of the strains showed a limited inhibition zone against Escherichia coli ATCC25922, and 26 strains against Salmonella enterica ATCC 14024, while 19 strains showed inhibition against one or all three Bacillus strains used as indicators. None of the tested strains showed an antimicrobial activity against Staphylococcus aureus ATCC 25923. Several strains showed antibacterial activity against more than one indicator strain. For instance, Lactobacillus plantarum 307, Lactobacillus brevis 308, and Lactobacillus plantarum/pentosus 358 were active against five of the indicator strains used, while other 23 LAB were active against three indicator strains. In the case of two strains, namely Leuconostoc citreum 344 and Lactobacillus brevis 183, the activity was maintained after neutralizing the pH of the cell-free supernatant likely due to the production of bacteriocins. The gel permeation chromatography-based screening revealed seven EPS-producing LAB strains. Two of the positive strains, namely Leuconostoc citreum 177 and Leuconostoc citreum 52, have been shown to produce large amounts of EPS, of about 20 g/L. All isolated EPS have a high molecular mass, of above 1400 KDa, and a monomer composition dominated by the presence of glucose.     

Carotenoids from tomatoes inhibit heterocyclic amine formation

Tomatoes are a rich source of antioxidants and they are commonly used for meat cooking in Mediterranean countries. The effects of tomato antioxidants on the formation of carcinogenic/mutagenic heterocyclic amines were investigated. A liquid model system containing as precursors creatinine, glucose and glycine in molar concentrations comparable to those present in bovine meat (chemical model system) was employed. A freeze-dried bovine meat juice (meat juice model system) was also used for some experiments. In both model systems, an inhibiting effect of tomato carotenoid fraction on the formation of imidazoquinolines (IQx, MeIQx and DiMeIQx) was observed. Using carotenoid extract at a concentration of 1000 ppm, inhibitions of 36% and 11% of IQx and MeIQx formation respectively in the chemical system and of 13% of MeIQx and of 5% of 4,8-DiMeIQx in the meat juice system was observed. The effect of the main tomato flavonoid, quercetin, was investigated using the meat juice system. Quercetin gave an inhibition of MeIQx formation between 9% and 57% with a maximum effect of 67% at 10 ppm.     

Characterization of melanoidins from a glucose-glycine model system

The properties of melanoidins prepared from glucose and glycine (GG) were investigated by a three step purification protocol consisting of dialysis, gel filtration at high ionic strength and ion metal affinity chromatography. The high molecular weight fraction obtained in the GG system is responsible for 80% of the total brown colour and its antioxidative ability was about 1/4 of that of Trolox measured by the inhibition of linoleic acid oxidation. GG melanoidins have good affinity towards Cu (II) (32% bound to the resin) while it is much lower towards Pb (II) (10%) and Fe (II) (5%). Capillary zone electrophoresis analysis suggests that GG melanoidins are positively charged, although no signal was observed analysing melanoidins by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF/MS).