169 research outputs found
Sierpinski carpet fractal monopole antenna for ultra-wideband applications
Microstrip antenna is broadly used in the modern communication system due to its significant features such as light weight, inexpensive, low profile, and ease of integration with radio frequency devices. The fractal shape is applied in antenna geometry to obtain the ultra-wideband antennas. In this paper, the sierpinski carpet fractal monopole antenna (SCFMA) is developed for base case, first iteration and second iteration to obtain the wideband based on its space filling and self-similar characteristics. The dimension of the monopole patch size is optimized to minimize the overall dimension of the fractal antenna. Moreover, the optimized planar structure is proposed using the microstrip line feed. The monopole antenna is mounted on the FR4 substrate with the thickness of 1.6 mm with loss tangent of 0.02 and relative permittivity of 4.4. The performance of this SCFMA is analyzed in terms of area, bandwidth, return loss, voltage standing wave ratio, radiation pattern and gain. The proposed fractal antenna achieves three different bandwidth ranges such as 2.6-4.0 GHz, 2.5-4.3 GHz and 2.4-4.4 GHz for base case, first and second iteration respectively. The proposed SCFMA is compared with existing fractal antennas to prove the efficiency of the SCFMA design. The area of the SCFMA is 25×20 mm2, which is less when compared to the existing fractal antennas
Characterization of the HIV-1 integrase chromatin- and LEDGF/p75-binding abilities by mutagenic analysis within the catalytic core domain of integrase
<p>Abstract</p> <p>Background</p> <p>During the early stage of HIV-1 replication, integrase (IN) plays important roles at several steps, including reverse transcription, viral DNA nuclear import, targeting viral DNA to host chromatin and integration. Previous studies have demonstrated that HIV-1 IN interacts with a cellular Lens epithelium-derived growth factor (LEDGF/p75) and that this viral/cellular interaction plays an important role for tethering HIV-1 preintegration complexes (PICs) to transcriptionally active units of host chromatin. Meanwhile, other studies have revealed that the efficient knockdown and/or knockout of LEDGF/p75 could not abolish HIV infection, suggesting a LEDGF/p75-independent action of IN for viral DNA chromatin targeting and integration, even though the underlying mechanism(s) is not fully understood.</p> <p>Results</p> <p>In this study, we performed site-directed mutagenic analysis at the C-terminal region of the IN catalytic core domain responsible for IN/chromatin binding and IN/LEDGF/p75 interaction. The results showed that the IN mutations H171A, L172A and EH170,1AA, located in the loop region <sub>170</sub>EHLK<sub>173 </sub>between the α4 and α5 helices of IN, severely impaired the interaction with LEDGF/p75 but were still able to bind chromatin. In addition, our combined knockdown approach for LEDGF/p75 also failed to dissociate IN from chromatin. This suggests that IN has a LEDGF/p75-independent determinant for host chromatin binding. Furthermore, a single-round HIV-1 replication assay showed that the viruses harboring IN mutants capable of LEDGF/p75-independent chromatin binding still sustained a low level of infection, while the chromatin-binding defective mutant was non-infectious.</p> <p>Conclusions</p> <p>All of these data indicate that, even though the presence of LEDGF/p75 is important for a productive HIV-1 replication, IN has the ability to bind chromatin in a LEDGF/p75-independent manner and sustains a low level of HIV-1 infection. Hence, it is interesting to define the mechanism(s) underlying IN-mediated LEDGF/p75-independent chromatin targeting, and further studies in this regard will help for a better understanding of the molecular mechanism of chromatin targeting by IN during HIV-1 infection.</p
A single cation or anion dendrimer-based liquid electrolyte
We propose here a novel liquid dendrimer-based single ion conductor as a potential alternative to conventional molecular liquid solvent-salt solutions in rechargeable batteries, sensors and actuators. A specific change from ester (-COOR) to cyano (-CN) terminated peripheral groups in generation-one poly(propyl ether imine) (G1-PETIM)-lithium salt complexes results in a remarkable switchover from a high cation (tLi+ = 0.9 for -COOR) to a high anion (tPF6- = 0.8 for -CN) transference number. This observed switchover draws an interesting analogy with the concept of heterogeneous doping, applied successfully to account for similar changes in ionic conductivity arising out of dispersion of insulator particle inclusions in weak inorganic solid electrolytes. The change in peripheral group simultaneously affects the effective ionic conductivity, with the room temperature ionic conductivity of PETIM-CN (1.9 × 10-5 Ω-1 cm-1) being an order of magnitude higher than PETIM-COOR (1.9 × 10-6 Ω-1 cm-1). Notably, no significant changes are observed in the lithium mobility even following changes in viscosity due to the change in the peripheral group. Changes in the peripheral chemical functionality directly influence the anion mobility, being lower in PETIM-COOR than in PETIM-CN, which ultimately becomes the sole parameter controlling the effective transport and electrochemical properties of the dendrimer electrolytes
Enhancing Wear Resistance in Al-7075 Composites Through Conventional Mixing and Casting Techniques
Aluminium 7075 alloy composite are highly sought after materials because of their superior strength, light weight and exhibiting enhanced tribological characteristics. An electric resistance furnace and the metal die process were used to develop this aluminium (Al 7075) alloy hybrid composites, with reinforcing provided by E-glass short fibres and aluminium oxide (Al2O3) particulates. The Al 7075 alloy composites have been cast by employing stirring technique at various weight percentages of E-glass short fibres (2%, 4%, 6%, and 8%) and Al2O3 particles (3%, 6%, 9%, and 12%). Microscopic examination demonstrates that Al2O3 particle distribution within Aluminium matrix has been uniform. Hardness of the in-situ Al-Al2O3-E-glass-based composites rose by 10.58%, 22.35%, 50.58%, and 41.17% in comparison to its base alloy. Tensile strength of the 2 to 8 wt.% E-glass with 3-12 wt.% Al2O3 stir-cast composites increased by 9.08%, 15.91%, 19.09%, and 7.27% when compared with the aluminium matrix, whereas ductility reduced by 8.9%, 12.5%, 18.75%, and 25%. An experiment on wear rate was carried out using a pin-on-disk benchtop test equipment. The examination was performed at varying weights and sliding speeds, and the resulted demonstrated that composite materials exhibit higher wear resistance than Al matrix. Furthermore, the presence of Al2O3 and E-glass resulted in lower wear loss across all applied loads and sliding velocities. Lower wear rates in these composites were attributed to hardness and the interfacial bonding between the Al alloy and the in-situ reinforcement
Dip coating of forsterite-hydroxyapatitie-poly (ɛ-caprolactone) nanocomposites on Ti6Al4Vsubstrates for its corrosion prevention
522-528Titanium and titanium alloys are extensively used in biomedical, cardiac and cardiovascular applications for their superb properties, such as good fatigue strength, low modulus, machinability, formability, corrosion resistance and biocompatibility. However, titanium and its alloys do not meet the majority of all clinical necessities. Due to these reasons, surface modification is frequently performed to enhance the mechanical, biological and chemical properties of titanium and alloys. In this work, nanocomposites coating of poly(ɛ-caprolactone)/hydroxyapatite/forsterite (PCL/HA/F) have been successfully deposited on the Ti6Al4V substratesby dip coating at room temperature. The coatings are prepared with various concentrations of forsterite/hydroxyapatite nanopowder (2, 4, 6 and 8 wt.%) with a fixed concentration of PCL (4 wt.%) and thus coated Ti6Al4V substrates are examined for corrosion resistance. PCL/Hydroxyapatite/Forsterite coatings are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which clearly showed the formation of nanocomposites. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) are used to investigate corrosion behavior of the coated substrates, which portrayed that the composite coating of PCL/HA/F substantially enhanced the corrosion resistance of Ti6Al4V alloy
Dip coating of forsterite-hydroxyapatitie-poly (ɛ-caprolactone) nanocomposites on Ti6Al4Vsubstrates for its corrosion prevention
Titanium and titanium alloys are extensively used in biomedical, cardiac and cardiovascular applications for their superb properties, such as good fatigue strength, low modulus, machinability, formability, corrosion resistance and biocompatibility. However, titanium and its alloys do not meet the majority of all clinical necessities. Due to these reasons, surface modification is frequently performed to enhance the mechanical, biological and chemical properties of titanium and alloys. In this work, nanocomposites coating of poly(ɛ-caprolactone)/hydroxyapatite/forsterite (PCL/HA/F) have been successfully deposited on the Ti6Al4V substratesby dip coating at room temperature. The coatings are prepared with various concentrations of forsterite/hydroxyapatite nanopowder (2, 4, 6 and 8 wt.%) with a fixed concentration of PCL (4 wt.%) and thus coated Ti6Al4V substrates are examined for corrosion resistance. PCL/Hydroxyapatite/Forsterite coatings are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which clearly showed the formation of nanocomposites. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) are used to investigate corrosion behavior of the coated substrates, which portrayed that the composite coating of PCL/HA/F substantially enhanced the corrosion resistance of Ti6Al4V alloy
Decadal variations of sea surface temperature in the eastern Arabian Sea and its impacts on the net primary productivity
Ten-year satellite derived data (January 2007 to
December 2016) were used to investigate the variability of
Chlorophyll-a (Chl-a), sea surface temperature (SST), net
primary production (NPP) in the eastern Arabian Sea (AS).
This study is aimed to show the coupling of physical and
biological processes to understand how temporal, annual
and inter-annual variations occur and the forcing mechanisms
behind these variations in the ocean environments.
This work is linked to Indian Ocean Dipole and the El
Nin˜o/Southern Oscillation, which frequently co-occur and
drives inter-annual changes within the AS. Vertically
Generalized Production Model was used to estimate NPP
using chl-a, Photosynthetically Available Radiation,
euphotic depth, and maximum photosynthetic rate from
SST. The relationship between NPP and SST showed
change in the pattern over the study period. The NPP in the
AS is characterized by an unusual decline during El Nin˜o
events. AS is more productive during summer monsoon
(June–September) due to coastal upwelling, wind driven
mixing and lateral advection processes. There was decline
in NPP after 2014 and this trend continued in the following
years. The present investigation revealed that the strong El
Nin˜o condition was observed in 2015 and productivity of
AS declined by * 19%, while SST increased by * 2%
from an overall average of 2007–2016. Increased SST and
low productivity could result in low fish catch in AS.
Increasing trend in SST could be attributed to the extreme
events like cyclones occurring along the west coast of
India
Morphological cells in the Ragusa littoral (Sicily, Italy)
Geomorphologic information, topographic maps
(dated 1967), aerial photographs (dated 1999 and 2008), and
spatial analysis procedures were used to investigate a 90 km
long coastal sector in South Sicily (Italy). Information was
obtained on coastal erosion/accretion areas, general sediment
circulation pattern and littoral cell distribution. Human-made
structures and natural headlands constituted important artificial
limits dividing littoral in morphological cells. Ports and
harbours were observed at Scoglitti, Punta Secca, Marina di
Ragusa, Donnalucata and Pozzallo. Most of them worked as
“transit” limits which interrupted predominant, eastward directed
sedimentary transport, this way generating accretion in
updrift (west) side of mentioned structures and erosion in
downdrift (east) side. During the 1967–2008 period, about
62,000 m2 and 42,000 m2 of beach surface were respectively
formed updrift of Scoglitti and Donnalucata ports. The construction
of Pozzallo port gave rise to the formation of a
“convergent” limit which favoured large accretion
(94,000 m2) east of port structure. Most important natural
structures were observed at Punta Zafaglione, P. Braccetto
and Cava d’Aliga. The knowledge of littoral cell distribution
acquires a great importance for appropriate management of
coastal erosion processes which may be mitigated installing
by-passing systems in ports and harbours and carrying out
nourishment works in eroding areas, often located downdrift
of ports and harbours (when these structures work as transit
limits) and in central part of littoral cells (when these structures
work as convergent limits)
An integrated approach to coastal erosion problems in northern Tuscany (Italy): Littoral morphological evolution and cell distribution
Occupation of the coast has significantly increased in recent decades, mostly due to a greater demand for
recreation and tourism. Today, erosion threatens many human-made structures and activities, requiring an
integrated approach for the understanding of coastal dynamics and identification of alternatives to associated
problems. This study investigates a 64 km-long coastal physiographic unit in the northern microtidal littoral
of Tuscany (Italy). Vertical aerial photographs and direct field surveys were used to retrieve changes in
shoreline position over 1938–1997 and 1997–2005 time intervals. Significant beach accretion was observed
during the first period updrift of Carrara (84 m) and Viareggio (280 m) harbours and at Marina di Pietrasanta
(100 m), whereas severe erosion occurred downcoast of Carrara harbour (−130 m, at Marina dei Ronchi) and
on the northern side of Arno river mouth (−400 m). Similar trends were observed between 1997 and 2005;
beach slope between the 1997 shoreline position and the closure depth correlated well with the distribution
of erosion/accretion patterns from the 1938–1997 period (slopes were lower in eroded areas than at sites
under accretion). Longshore distribution of erosion/accretion patterns was controlled by coastal compartmentalisation.
Three of the main littoral cells were mostly formed by natural limits (i.e., Punta Bianca
promontory, Marina di Pietrasanta, the Arno river mouth and the port of Livorno). Several sub-cells were
created within these cells due to the introduction of human-made structures (such as Carrara and Viareggio
harbours), which formed artificial fixed limits that allowed the transport of sediments (exclusively fines) in
one direction only. Results will help improve the understanding of coastal processes and manage littoral
sediment transport in a sustainable manner. This will reduce the need for structural interventions, such as
breakwaters and groynes, which in the past decades prevented coastal retreat at local scale but shifted erosion
downdrift, leading to degradation of the investigated area and requiring continuous maintenance
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