Polyhydroxyalkanoate (PHA): Review of synthesis, characteristics, processing and potential applications in packaging

Polyhydroxyalkanoates (PHAs) are gaining increasing attention in the biodegradable polymer market due to their promising properties such as high biodegradability in different environments, not just in composting plants, and processing versatility. Indeed among biopolymers, these biogenic polyesters represent a potential sustainable replacement for fossil fuel-based thermoplastics. Most commercially available PHAs are obtained with pure microbial cultures grown on renewable feedstocks (i.e. glucose) under sterile conditions but recent research studies focus on the use of wastes as growth media. PHA can be extracted from the bacteria cell and then formulated and processed by extrusion for production of rigid and flexible plastic suitable not just for the most assessed medical applications but also considered for applications including packaging, moulded goods, paper coatings, non-woven fabrics, adhesives, films and performance additives. The present paper reviews the different classes of PHAs, their main properties, processing aspects, commercially available ones, as well as limitations and related improvements being researched, with specific focus on potential applications of PHAs in packaging

Electron-phonon interaction at the Be(0001) surface

We present a first principle study of the electron-phonon (e-p) interaction at the Be(0001) surface. The real and imaginary part of the e-p self energy are calculated for the surface state in the binding energy range from the $\bar{\Gamma}$ point to the Fermi level. Our calculation shows an overall good agreement with several photoemission data measured at high and low temperatures. Additionally, we show that the energy derivative of real part of the self-energy presents a strong temperature and energy variation close to $E_{F}$, making it difficult to measure its value just at $E_{F}$.Comment: Accepted in Phys. Rev. Lett., 5 figure

The Raman Fingerprint of Graphene

Graphene is the two-dimensional (2d) building block for carbon allotropes of every other dimensionality. It can be stacked into 3d graphite, rolled into 1d nanotubes, or wrapped into 0d fullerenes. Its recent discovery in free state has finally provided the possibility to study experimentally its electronic and phonon properties. Here we show that graphene's electronic structure is uniquely captured in its Raman spectrum that clearly evolves with increasing number of layers. Raman fingerprints for single-, bi- and few-layer graphene reflect changes in the electronic structure and electron-phonon interactions and allow unambiguous, high-throughput, non-destructive identification of graphene layers, which is critically lacking in this emerging research area

BMI from nutritional surveillance of 8-9 years old children in Tuscany (Italy)

Introduction. The latest increase in childhood obesity focused attention on the important consequences that this phenomenon may have on public health in relationship to the increasing risk that an obese child may become an obese adult. To deal with this problem, there is necessary to assess systematically the distribution of childhood nutritional status at different levels: international, regional and local. In this paper are presented data on underweight, overweight and obesity prevalence in third grade primary school children, aged 8/9 years in Tuscany (2008) and its distribution in relationship to the demographic breadth of their place of residence. Methods. Data from statistic sample of 2109 (1.091 males, 1.018 females), 8/9 years school-children were collected; weight and height were measured using standardised personnel and instruments. Exact month age was calculated between the data of measurement and that of birth. Body Mass Index (BMI) classes were calculated using Cole et al.?s epidemiologic cut-off for children and adolescents. Residence areas were divided into four classes based on the number of inhabitants ( inf. 10.000; 10.000-50.000; > 50.000; > 50.000 metropolitan). Results. The prevalence of underweight was 0.88% (0.76% in males and 1.01% in females), the prevalence of overweight was 23.43% (22.33% in males and 24.65% in females), the prevalence of obese was 7.95% (9.08% in males, 6.70% in females). The lowest prevalence of obese (6.46%) was found in towns with over 50.000 residents (metropolitan). Conclusion. The obesity prevalence in Tuscany children is still lower than that of the Italian National Survey, while the overweight prevalence it?s the same. Obesity prevalence (10.71%) is higher in municipalities with low residents number ( inf. 10.000)

Evaluation of mechanical and interfacial properties of bio-composites based on poly(lactic acid) with natural cellulose fibers

The circular economy policy and the interest for sustainable material are inducing a constant expansion of the bio-composites market. The opportunity of using natural fibers in bio-based and biodegradable polymeric matrices, derived from industrial and/or agricultural waste, represents a stimulating challenge in the replacement of traditional composites based on fossil sources. The coupling of bioplastics with natural fibers in order to lower costs and promote degradability is one of the primary objectives of research, above all in the packaging and agricultural sectors where large amounts of non-recyclable plastics are generated, inducing a serious problem for plastic disposal and potential accumulation in the environment. Among biopolymers, poly(lactic acid) (PLA) is one of the most used compostable, bio-based polymeric matrices, since it exhibits process ability and mechanical properties compatible with a wide range of applications. In this study, two types of cellulosic fibers were processed with PLA in order to obtain bio-composites with different percentages of microfibers (5%, 10%, 20%). The mechanical properties were evaluated (tensile and impact test), and analytical models were applied in order to estimate the adhesion between matrix and fibers and to predict the material's stiffness. Understanding these properties is of particular importance in order to be able to tune and project the final characteristics of bio-composites

Underweight and overweight among children and adolescents in Tuscany (Italy). Prevalence and short-term trends

Introduction. The recent increase in both childhood obesity and adolescent anorexia nervosa in developed countries has under-lined the important consequences that these trends may have on public health, as there is an increased risk that these conditions may become chronic diseases in adulthood. Therefore, it is necessary to monitor prevalence rates and trends in thinness and overweight (including obesity) among children and adolescents at different levels: international, national and sub-national. Since 2001/2002, a nutritional surveillance system has been implemented in the Tuscany Region to estimate the nutritional status and lifestyles of children and adolescents. The main objectives were to assess the prevalence of thinness, overweight and obesity among Tuscan children and adolescents and to provide baseline information on the prevalence of thinness, for the first time calculated according to the new international definitions, for geographical comparisons and descriptions of time trends. Methods. Independent cross-sectional sample surveys were conducted in 2002, 2004 and 2006 in Tuscany, North-Central Italy. Data were collected from stratified two-stage cluster samples of children aged 9 years (n = 3,048 in 2002 and n = 1,430 in 2006) and of adolescents aged 11-13-15 years (n = 1,066, n = 1185 and n = 1,160 in 2004 and n = 1,189, n = 1,211 and n = 1,178 in 2006, respectively). Weights and heights of primary school children were measured by means of standardized methods, while those of adolescents were self-reported. Decimal age was calculated from the date of birth to the date of measurement. Body Mass Index classes were calculated according to the International Obesity Task Force standards. Instead of the term underweight in children, we used the term thinness, which the World Health Organization uses to mean low Body Mass Index for age in adults and adolescents. According to Cole?s recently published cut-offs for thinness, we divided our Body Mass Index values below 18.5 into three grades. Results. This study presents data on the prevalence of different grades of nutritional status (thinness, normal weight, overweight and obesity) among Tuscan school-aged children from primary to high school (9-11-13-15-y-old), assessed by means of Body Mass Index, according to international definitions. From 2002 to 2006 the prevalence of thinness among children aged 9 years decreased from 4.6% to 4.2%, and the prevalence of normal weight from 63.7% to 62.4%; the prevalence of overweight (including obesity) rose from 31.7% to 33.4%. From 2004 to 2006, among pre-adolescents aged 11 years, the prevalence of thinness declined from 11.0% to 10.1%; the prevalence of normal weight rose from 68.4% to 70.2%, and the prevalence of overweight declined from 20.7% to 19.6%. Among adolescents aged 13 years, the prevalence of thinness declined from 9.8% to 8.0%; the prevalence of normal weight rose from 73.5% to 74.0%, and the prevalence of overweight from 16.8% to 17.9%. Among adolescents aged 15 years, the prevalence of thinness declined from 9.8% to 8.7%, and the prevalence of normal weight from 77.0% to 71.6%, while the prevalence of overweight rose from 13.3% to 19.7%. The 2006 data showed that the trend in the prevalence of overweight (including obesity) tended to decrease with age for both sexes, though more markedly in girls (from 34.0% at 9-y of age to 12.2% at 15-y of age) than in boys (from 32.8% at 9-y of age to 22.8% at 13-y of age to 27.5% at 15-y of age). By contrast, the prevalence of thinness increased with age in girls (from 4.9% at 9-y of age to 14,1% at 15-y of age), while boys presented a similar low prevalence at 9 and 15-y of age (3.3% and 3.1%), doubling the values at 11 and 13-y of age (7.5% and 6.5%). The trend in the prevalence of normal weight increased with age from 62.4% at 9-y of age to 74.0% at 13-y of age and to 71.6% at 15-y of age. Boys displayed a higher prevalence than girls only at 9-y of age (63.9% vs. 61.0%). Discussion. The results of this study allow us to analyze data from the nutritional surveillance system in Tuscany using recent definitions of Body Mass Index cut-off points among children, pre-adolescents and adolescents. As a rule, the trend in the prevalence of overweight (including obesity) among girls from 9-y to 15-y-old strongly decreased, while the prevalence of thinness increased. In boys, this decrease was less marked and the prevalence of thinness displayed an irregular trend, with an increment from 9-y to 11-y-old and a decrease from 13-y to 15-y old. The trend in the prevalence of normal weight increased with age, with a higher prevalence among boys than girls

Formation of p-n junction in polymer electrolyte-top gated bilayer graphene transistor

We show simultaneous p and n type carrier injection in bilayer graphene channel by varying the longitudinal bias across the channel and the top gate voltage. The top gate is applied electrochemically using solid polymer electrolyte and the gate capacitance is measured to be 1.5 $\mu F/cm^2$, a value about 125 times higher than the conventional SiO$_2$ back gate capacitance. Unlike the single layer graphene, the drain-source current does not saturate on varying the drain-source bias voltage. The energy gap opened between the valence and conduction bands using top and back gate geometry is estimated.Comment: 16 pages, 6 figure

Evaluation of mussel shells powder as reinforcement for pla-based biocomposites

The use of biopolyesters, as polymeric matrices, and natural fillers derived from wastes or by-products of food production to achieve biocomposites is nowadays a reality. The present paper aims to valorize mussel shells, 95% made of calcium carbonate (CaCO3 ), converting them into high-value added products. The objective of this work was to verify if CaCO3, obtained from Mediterranean Sea mussel shells, can be used as filler for a compostable matrix made of Polylactic acid (PLA) and Poly(butylene adipate-co-terephthalate) (PBAT). Thermal, mechanical, morphological and physical properties of these biocomposites were evaluated, and the micromechanical mechanism controlling stiffness and strength was investigated by analytical predictive models. The performances of these biocomposites were comparable with those of biocomposites produced with standard calcium carbonate. Thus, the present study has proved that the utilization of a waste, such as mussel shell, can become a resource for biocomposites production, and can be an effective option for further industrial scale-up

Mechanisms of gastroprotection by lansoprazole pre-treatment against experimentally induced injury in rats: role of mucosal oxidative damage and sulfhydryl compounds

This study investigated the mechanisms involved in the protective actions exerted by lansoprazole against experimental gastric injury. Following the intraluminal injection of ethanol-HCl, the histomorphometric analysis of rat gastric sections demonstrated a pattern of mucosal lesions associated with a significant increase in the mucosal contents of malondialdehyde and 8-iso-prostaglandin F(2alpha) (indices of lipid peroxidation), as well as a decrease in the levels of mucosal sulfhydryl compounds, assayed as reduced glutathione (GSH). Pretreatment with lansoprazole 90 micromol/kg, given intraduodenally as single dose or once daily by intragastric route for 8 days, significantly prevented ethanol-HCl-induced gastric damage. The concomitant changes in the mucosal levels of malondialdehyde, 8-iso-prostaglandin F(2alpha) and GSH elicited by ethanol-HCl were also counteracted by lansoprazole. In separate experiments, performed on animals undergoing 2-h pylorus ligation, lansoprazole did not enhance the concentration of prostaglandin E(2), bicyclo-prostaglandin E(2), or nitric oxide (NO) metabolites into gastric juice. Western blot analysis revealed the expression of both type 1 and 2 cyclooxygenase (COX) isoforms in the gastric mucosa of pylorus-ligated rats. These expression patterns were not significantly modified by single-dose or repeated treatment with lansoprazole. Lansoprazole also exhibited direct antioxidant properties by reducing 8-iso-prostaglandin F(2alpha) generation in an in vitro system where human native low-density lipoproteins were subjected to oxidation upon exposure to CuSO(4). The present results suggest that the protective effects of lansoprazole can be ascribed to a reduction of gastric oxidative injury, resulting in an increased bioavailability of mucosal sulfhydryl compounds. It is also proposed that lansoprazole does not exert modulator effects on the gastric expression of COX isoforms as well as on the activity of NO pathways