Path-independent integrals around two circular holes in an infinite plate under biaxial loading conditions

An analytic solution is presented for stresses induced in an infinite plate with two unequal circular holes by remote uniform loadings and arbitrary internal pressures in the holes. The solution is obtained by using the general expression for a biharmonic function in bipolar coordinates. The Airy stress function is decomposed in the sum of a fundamental stress function for an infinite plate remotely loaded, which gives non vanishing tractions on the circular boundaries, and an auxiliary stress function required to satisfy the boundary conditions on the pressures at the edges of the holes, which produces vanishing stresses at infinity. Correspondingly, the variations of the stress concentration factor are determined in terms of the holes geometry and loading conditions. The path independent J_k- (k = 1, 2), M- and L-integrals are analytically calculated on a closed contour encircling the two holes, under remote loading, in order to evaluate the energy release rates accompanying unit translation, self similar expansion and rotation of the holes, respectively. Results are then presented for varying loading orientation angle, biaxial loading ratio and holes geometry.     

Antimicrobial activity of chitosan nanofibers obtained by electrospinning

Chitosan is a natural polymer with both antimicrobial activity and nanofiber‐forming capability. The electrospinning technique allows the production of chitosan nanofibers but still faces several problems such as the small number of suitable solvents for the process and the large number of factors affecting quality and production of the nanofibers, among others. The antimicrobial properties of chitosan nanofibers have been little studied; therefore, the most probable mechanism of action and the effect of the conformation or arrangement of the molecules in the nanofibers remain unknown. The presence of residual solvent in the materials is one factor that has complicated the assessment of the antimicrobial activity of chitosan nanofibers. The research in this area will be very important for the future of these materials. Copyright © 2011 Society of Chemical Industry     

Weekly high‐dose ergocalciferol to correct vitamin D deficiency/insufficiency in hemodialysis patients: A pilot trial

Controversy exists on which vitamin D (D2 or D3) and which dosage scheme is the best to obtain and maintain adequate 25 OH D levels in dialysis patients safely. We tried to determine whether high‐dose vitamin D2 supplementation could obtain optimal vitamin D status without inducing hypercalcemia. We studied 82 patients on dialysis not taking active vitamin D therapy and supplemented them with oral vitamin D2 72,000 IU/week for 12 weeks followed by 24,000 IU/week as maintenance therapy during 36 weeks. By week 12, serum 25(OH)D increased from 15.2 ± 5.4 to 42.5 ± 13.2 ng/mL (P < 0.01) at week 12 and remained optimal (34.7 ± 12.0); 84.8% of the patients reached values ≥30 ng/mL. iPTH and alkaline phosphatase did not change at 48 weeks compared with baseline, but bone alkaline phosphatase decreased significantly (54.3 ± 46.0 to 44.3 ± 25.0; P = 0.02). Uncorrected serum Ca increased significantly at the end of follow‐up (9.03 ± 0.42 to 9.14 ± 0.62; P = 0.04); hypercalcemia was presented in two patients in the first control visit (week 12), in one patient in the second control (week 30), and in one patient in the third control (week 48). In 222 serum calcium determinations during follow‐up, hypercalcemia was observed in only 1.8% of cases. This vitamin D2 oral regimen with initial high doses was safe and sufficient to obtain and maintain optimal serum 25(OH)D concentrations and prevent vitamin D insufficiency in chronic kidney disease patients on dialysis.     

Molybdenum oxide anode buffer layers for solution processed,blue phosphorescent small molecule organic light emitting diodes

In this work we present solution processed organic light emitting diodes (OLEDs) comprising small molecule, blue phosphorescent emitter layers from bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium doped 4,4′,4″-tris(carbazol-9-yl)-triphenylamine and molybdenum trioxide (MoO₃) anode buffer layers. The latter were applied from a molybdenium(V)ethoxide precursor solution that was thermally converted to MoO₃ at moderate temperatures. The high work function MoO₃ facilitated hole injection into the emission layer. The MoO₃ layer properties were investigated by means of energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy. MoO₃ buffer layers performed superior to the commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and enabled an enhanced OLED device efficiency.     

Energy Efficiency of Error Control for High Data Rate WPAN

This paper addresses the issue of energy efficiency for error control mechanisms over WPAN systems. An analytical formulation has been developed to study the trade-off between link layer performance and energy consumption for two types of error control schemes: pure ARQ and type II hybrid ARQ protocol. An MC-CDMA-based system is considered. First of all, the analysis has been used to compare different error recovery schemes from the energy efficiency point of view. Moreover, it has been found that, for any channel conditions, there exists an optimal value of the transmit power that maximizes the energy efficiency. The paper also shows how this result can be used to design the power control of an energy efficient CDMA-based communication system. Mauro De Sanctis received the “Laurea' degree in Telecommunications Engineering from the University of Roma “Tor Vergata' in 2002. He is currently a Ph.D. Student and Assistant Professor in the Department of Electronics Engineering of the same University. He is involved in the DAVID (DAta and Video Interactive Distribution) satellite mission of the ASI (Italian Space Agency); his research is funded by the ASI. He is also involved in the MAGNET (My personal Adaptive Global NET) European FP6 integrated project and in the SatNEx European network of excellence. He worked on Italian national research projects on satellite-terrestrial systems integration such as SHINES (Satellite and HAP Integrated NEtworks and Services) and CABIS (CDMA for Broadband mobile terrestrial-satellite Integrated Systems). On autumn 2004 he joined the CTIF (Center for TeleInFrastructure), a research center focusing on modern telecommunications technologies located at the University of Aalborg (Denmark). His main areas of interest are: integration of different satellite networks, stratospheric platforms and terrestrial networks in a multi-layered fashion, internetworking and resource management in satellite systems and energy efficiency of WPAN systems. Simone Quaglieri received the “Laurea' degree cum laude in Telecommunications Engineering from the University of Roma “Tor Vergata', Italy, in 2004. His thesis, concerning the study of an analytic model for the Raman amplifier in optical systems with high bit rate, has been developed in the same University. During 2002 he worked as stagiaire on the design and development of optical submarine systems at the Elettra company (Telecom Italia group, Italy). He is joining the IRIS (Innovative Radio Integrated Systems) group at the University of Roma “Tor Vergata' as Research Engineer, where he is working on MC-CDMA based technology in the frame of the MAGNET (My Adaptive Global NETwork) European project. He is also working on error recovery mechanisms over satellite systems, and his research is funded by the EC in the frame of the SatNEx (Satellite Network of Excellence) European project. Ernestina Cianca graduated cum laude in Electronics Engineering in 1997 at the University of L'Aquila. She was with Italtel/Siemens (L'Aquila) from 1997 to 1998. She got her Ph.D. degree from the University of Rome Tor Vergata (URTV). The thesis work was on power management in CDMA-based satellite systems. She has been employed by the University of Aalborg, Denmark, in the Wireless Networking Groups (WING), as Research engineer (2000–2001) and as Assistant Professor (2001–2003). In particular, from Sept. 2002 she has been Technical Manager of Aalborg University for the IST-STRIKE project. She is currently Assistant Professor in Telecommunications at the URTV (Dpt. of Electronics Engineering), teaching DSP, Information and Coding. Her research mainly concerns wireless access technologies (CDMA and MIMO-OFDM-based systems), in particular, Radio Resource Management at PHY/MAC layer, ARQ/HARQ, TCP-IP issues over wireless links, integration of terrestrial and satellite systems. She has been the vice-coordinator of the following national research programs: CABIS, on CDMA integrated mobile systems (2000-2002) and SHINES, on satellite-HAP integrated networks for multimedia applications co-financed by MIUR (2002–2004). She is currently working on various European Projects: EU FP6 IP MAGNET (My personal Adaptive Global NET); EU ASIA LINK EAGER-NetWIC (Euro-Asian Network for Strengthening Graduate Education and Research in Wireless Communications); EU Network of excellence NEXWAY. She is author of about 40 papers, on international journals/transactions and proceedings of international conferences. Marina Ruggieri graduated in Electronics Engineering in 1984 at the University of Roma. She was: with FACE-ITT and GTC-ITT (Roanoke, VA) in the High Frequency Division (1985–1986); Research and Teaching Assistant at the University of Roma Tor Vergata (URTV) (1986–1991); Associate Professor in Telecommunications at the University of L'Aquila (1991–1994). Since November 2000 she is Full Professor in Telecommunications at the URTV (Dpt. of Electronics Engineering), teaching DSP, Information and Coding. In 1999 she has been appointed member of the Board of Governors of the IEEE AES Society (2000–2002) and re-elected for the period 2003–2005. Her research mainly concerns space communications and navigation systems (in particular satellites) as well as mobile and multimedia networks. She is the Principal Investigator of: satellite scientific communications missions (DAVID, WAVE) of ASI; national research programs (CABIS) on CDMA integrated mobile systems (2000–2002) and on satellite-HAP integrated networks for multimedia applications (SHINES), co-financed by MIUR (2002–2004). She co-ordinates the URTV Unit in various European Projects: EU FP6 IP MAGNET (My personal Adaptive Global NET); EU ASIA LINK EAGER-NetWIC (Euro-Asian Network for Strengthening Graduate Education and Research in Wireless Communications); EU Network of excellence NEXWAY; GALILEO JU 1st Call – July 2003: VERT (VEhicular Remote Tolling); and in the ASI program on V-band payloads (TRANSPONDERS). She is member of the Editorial Board of Wireless Personal Communications – an International Journal (Kluwer). She was awarded the 1990 Piero Fanti International Prize and she had a nomination for the Harry M. Mimmo Award in 1996 and the Cristoforo Colombo Award in 2002. She is author of about 170 papers, on international journals/transactions and proceedings of international conferences, book chapters and books.     

Adaptogenic effect of black and fermented leaves of Bergenia crassifolia L. in mice

The adaptogenic effect of Bergenia crassifolia black and fermented leaves was examined based on the forced swimming capacity and the change of biochemical parameters in mice. The treatment groups were orally administered infusions of black and fermented leaves of 3 populations of B. crassifolia, while the control group received distilled water for 7 days. Infusions from black leaves of B. crassifolia insignificantly enhanced the maximum swimming capacity of mice by increasing fat utilization, and by delaying the accumulation of plasma lactate while infusions from fermented leaves of B. crassifolia significantly enhanced the maximum swimming capacity of mice without change of the body weight by increasing glucose utilization and decreasing lactate level compared to the control group.     

Integrated analysis of non-linear loss mechanisms in Yb:YAG ceramics for laser applications

Transparent 9.8 at% Yb:YAG ceramic samples were prepared by reactive sintering of commercial oxides and using 0 or 1 wt% polyethylene glycol (PEG) as dispersant. The optical quality of the samples turns out to be improved by using a dispersant and optical transmittance close to the commercial samples has been obtained. On the other hand the laser characterization evidenced the activation of a non-linear loss mechanism occurring only in the sample containing PEG and despite its better optical quality, at high excitation level. A SEM analysis of material microstructure could not explain this behavior. A state of the art TEM analysis at nanometric scale was performed providing high resolution chemical spectroscopic results that indicate the presence of amorphous and crystalline silicate phases playing different roles in the two samples.     

Superhard transparent hybrid nanocomposites for high fidelity UV-nanoimprint lithography

Transparent hyperbranched acrylate nanocomposites were produced using different combinations of silica nanoparticles and silicon-based sol–gel precursors. The nanocomposites were processed using a dual-cure UV polymerization and condensation scheme. The viscosity of hybrid suspensions was found to be one to two orders of magnitude lower than that of particulate composites with the same equivalent silica fraction. The Vickers microhardness of the polymer was 112 MPa. It was equal to 190 MPa and 148 MPa for the hybrid composites and particulate composites with 20 vol% SiO₂, respectively, and it was equal to 287 MPa for the hybrid material with 30 vol% SiO₂. Light-trapping textures in the form of random sub-micron pyramidal features were replicated in the hybrid composites from a nickel template using UV-nanoimprint lithography. After optimization of the dual-cure process sequence, a very high replication fidelity was obtained for all investigated compositions, leading to a haze above 99% over the visible light spectrum and a very effective light scattering performance in a broad angular exposure.     

Clustering in the Creative Industries: Insights from the Origins of Computer Software

We use several different sources (a 1970 Roster of Organizations in Data Processing and the 1960 and 1970 Censuses of Population) to study patterns of geographic clustering at the very origins of the software industry. We find a strong trend toward clustering of the industry in a few metropolitan areas. Furthermore, we uncover a tendency in the early software industry to agglomerate in close proximity to some of its main customers. This tendency holds even after controlling for region-specific heterogeneity and for the potentially endogenous nature of the software customers' location decisions. We explore the factors that may have driven the observed clustering patterns and suggest directions for further research.