Research Interest In Recent Times Research Articles

Assessing Riyadh’s Urban Change Utilizing High-Resolution Imagery

The implications of change on local processes have attracted significant research interest in recent times. In urban settings, green spaces and forests have attracted much attention. Here, we present an assessment of change within the predominantly desert Middle Eastern city of Riyadh, an understudied setting. We utilized high-resolution SPOT 5 data and two classification techniques—maximum likelihood classification and object-oriented classification—to study the changes in Riyadh between 2004 and 2014. Imagery classification was completed with training data obtained from the SPOT 5 dataset, and an accuracy assessment was completed through a combination of field surveys and an application developed in ESRI Survey 123 tool. The Survey 123 tool allowed residents of Riyadh to present their views on land cover for the 2004 and 2014 imagery. Our analysis showed that soil or ‘desert’ areas were converted to roads and buildings to accommodate for Riyadh’s rapidly growing population. The object-oriented classifier provided higher overall accuracy than the maximum likelihood classifier (74.71% and 73.79% vs. 92.36% and 90.77% for 2004 and 2014). Our work provides insights into the changes within a desert environment and establishes a foundation for understanding change in this understudied setting.

Effects of Various Graphite Cathodes on Self-Discharge Behavior of Rechargeable Aluminum Batteries

Renewable energy technologies, such as wind power and solar energy, have become great importance in modern society [1]. Unfortunately, the intermittent nature of these energies leads to a huge barrier in energy generation and stabilization in electricity supply [2]. The rechargeable batteries received a lot of attention due to high energy density and satisfactory cycle life. Rechargeable aluminum batteries (RABs) gain a great amount of research interest in recent times due to the low cost of aluminum compared to that of lithium. Aluminum, being the most abundant metal in the earth crust, has three-electron transfer characteristic, high volumetric capacity, and great safety, which make RABs suitable for large-scale energy storage [3]. However, problems like low discharge voltage, high corrosion of electrolyte, serious self-discharge impede the growth and development of RABs. Jiao’s group demonstrated self-discharge phenomena for Ah-level RABs, where self-discharge rate was about 6%/day [4]. Their research only presented the self-discharge phenomena, but not studied the factors affecting self-discharge behavior. Self-discharge is an important issue for practical applications. The self-discharge rate of RABs is much higher than that of commercial lithium-ion batteries, whose self-discharge rate is approximately 5%/month. It is thus necessary to investigate the factors affecting self-discharge properties of RABs. In this work, effects of various types of graphite cathodes on charge-discharge properties and self-discharge behavior in ionic liquid electrolyte are studied. The results demonstrate that the changes in d-spacing and morphology of the graphite are crucial. The phase transformation of the graphite cathode during charging/discharging and self-discharge is examined using in-situ X-ray diffraction (performed at National Synchrotron Radiation Research Centre, Taiwan). The reaction mechanism is discussed in details.

Effects of surface roughness on mixed convection nanoliquid flow over slender cylinder with liquid hydrogen diffusion

The influence of surface roughness on boundary layer flow characteristics over moving surfaces is of considerable research interest in recent times. In the present study, the effects of surface roughness on flow over moving slender cylinder are analyzed in presence of mixed convection nanoliquid boundary layer flow. The problem is modelled in terms of highly nonlinear dimensional partial differential equations, which are written in non-dimensional form with the help of non-similar transformations. The resulting equations are reduced to linear partial differential equations by utilizing Quasilinearization technique, which are discretized using implicit finite difference scheme. The results obtained during the numerical simulation are then depicted through graphs in terms of various profiles and gradients and are analyzed with proper physical explanations. The roughness of slender cylinder surface is represented in a deterministic model as a sine wave form and yields sinusoidal variations in the values of skin-friction coefficient, wall heat and mass transfer rates. It is observed that the surface roughness effects are more prominent away from the orifice. The local frequency of gradients increases (i.e. wavelength decreases) with the increase in the frequency of surface roughness (n). The addition of nanoparticles into the ordinary fluid enhances the skin-friction coefficient and wall mass transfer rate. However, due to its effects, significant reduction is observed in the wall heat transfer rate. The phase difference of gradient oscillations arising in presence of nanoparticles is suppressed further away from the origin due to surface roughness. Interestingly, the amplitude of gradient oscillations remain higher in case of nanoliquid in comparison with that in case of ordinary fluid. Furthermore, the magnitude of wall mass transfer rate of liquid hydrogen is higher than that of nanoparticle wall mass transfer rate, which signifies the higher diffusivity of nanoparticles. The results of present study are of practical relevance to industrial applications such as polymer fibre coating and coating of wires.

Artificial light-harvesting systems fabricated by supramolecular host–guest interactions

Artificial light-harvesting systems (LHSs) have drawn increasing research interest in recent times due to the energy crisis worldwide. Concurrently, macrocycle-based host–guest interactions have played an important role in the development of supramolecular chemistry. In recent years, studies towards artificial LHSs driven by macrocycle-based host–guest interactions are gradually being disclosed. In this mini-review, we briefly introduce the burgeoning progress of artificial LHSs driven by host–guest interactions. We believe that an increasing number of reports of artificial LHSs driven by host–guest interactions will appear in the near future and will provide a viable alternative for the future production of renewable energy.

DF Relayed Subcarrier FSO Links over Malaga Turbulence Channels with Phase Noise and Non-Zero Boresight Pointing Errors

Subcarrier free-space optical (FSO) systems using coherent recovery techniques at the receiver have acquired growing research interest in recent times. However, their optimal performance is diminished by the non-perfect synchronization of carrier frequency and phase, which is mainly due to phase noise problems. Moreover, turbulence and pointing error effects further deteriorate the overall performance. However, relay transmission schemes can extend the coverage distance and offer substantial improvements over fading conditions. In this respect, we consider a serially relayed network using decode-and-forward relays, and investigate its performance by means of average symbol error probability and mean outage duration. Turbulence is modeled by the recently unified M(alaga) distribution, which constitutes a very general statistical model that accurately describes the irradiance fluctuations from weak-to-strong turbulence conditions. Additionally, the presence of non-zero boresight pointing errors due to misalignment between the transmitter–receiver pair is considered, while the effect of phase noise is specified by a Tikhonov distribution. A comparison between single line-of-sight and serially relayed FSO configurations is provided as well. Novel approximated mathematical expressions are deduced, which are proved to be accurate enough over a wide range of turbulence strengths and signal-to-noise values. Finally, proper numerical results are presented and validated by Monte Carlo simulations.

Strong visible and near infrared photoluminescence from ZnO nanorods/nanowires grown on single layer graphene studied using sub-band gap excitation

Fabrication and optoelectronic applications of graphene based hybrid 2D-1D semiconductor nanostructures have gained tremendous research interest in recent times. Herein, we present a systematic study on the origin and evolution of strong broad band visible and near infrared (NIR) photoluminescence (PL) from vertical ZnO nanorods (NRs) and nanowires (NWs) grown on single layer graphene using both above band gap and sub-band gap optical excitations. High resolution field emission scanning electron microscopy and X-ray diffraction studies are carried out to reveal the morphology and crystalline quality of as-grown and annealed ZnO NRs/NWs on graphene. Room temperature PL studies reveal that besides the UV and visible PL bands, a new near-infrared (NIR) PL emission band appears in the range between 815 nm and 886 nm (1.40–1.52 eV). X-ray photoelectron spectroscopy studies revealed excess oxygen content and unreacted metallic Zn in the as-grown ZnO nanostructures, owing to the low temperature growth by a physical vapor deposition method. Post-growth annealing at 700 °C in the Ar gas ambient results in the enhanced intensity of both visible and NIR PL bands. On the other hand, subsequent high vacuum annealing at 700 °C results in a drastic reduction in the visible PL band and complete suppression of the NIR PL band. PL decay dynamics of green emission in Ar annealed samples show tri-exponential decay on the nanosecond timescale including a very slow decay component (time constant ∼604.5 ns). Based on these results, the NIR PL band comprising two peaks centered at ∼820 nm and ∼860 nm is tentatively assigned to neutral and negatively charged oxygen interstitial (Oi) defects in ZnO, detected experimentally for the first time. The evidence for oxygen induced trap states on the ZnO NW surface is further substantiated by the slow photocurrent response of graphene-ZnO NRs/NWs. These results are important for tunable light emission, photodetection, and other cutting edge applications of graphene-ZnO based 2D-1D hybrid nanostructures.

Human Papilloma Virus in Oral Cavity Cancer and Relation to Change in Quality of Life Following Treatment-a Pilot Study from Northern India.

Human papilloma virus (HPV)-associated head and neck cancer (HNC) has generated significant amount of research interest in recent times with focus shifted to oral cavity squamous cell cancer (OCSCC) after oropharyngeal cancer. Due to high incidence of OCSCC and anecdotal reports on association of HPV infection from northern region of India, this study was conceived to investigate HPV infection and establish its association with lifestyle habits such as tobacco, alcohol consumption, oro-genital sex, number of sexual contacts, and change in quality of life posttreatment. A total of 43 primary OCSCC biopsy specimens were collected. These samples were analyzed for HPV DNA genotyping which was done by using 13 high-risk HPV real-time PCR kits. Quality of life was assessed using University of Washington questionnaire for HNC patients, which was administered pretreatment and 3-months posttreatment. HPV presence was confirmed in only three patients (7.0%). HPV positivity did not find any statistical correlation with age, gender, residence, addiction habit, stage, tumor size, nodal status, tumor grade, and number of sexual contacts. There was no significant (p>0.05) difference in the average percent change in QOL parameters from pretreatment to posttreatment when correlated with HPV status.

Palladium catalyzed selective distal C-H olefination of biaryl systems.

Palladium catalyzed selective distal C-H activation with nitrile based templates has been of significant research interest in recent times. In this report, we disclose the distal C-H olefination of biphenyl systems with high regio- and stereo-selectivity and useful synthetic yields. The utility of this method has been demonstrated through its wide olefin scope, its operation at the gram scale and the easy removal/recovery of the directing group.

Production of Biofuel Additives from Esterification and Acetalization of Bioglycerol over SnO2-Based Solid Acids

Owing to significant environmental and economical concerns of fossil fuels, the search for alternative renewable fuels has received a explicit research interest in recent times. In this work, we prepared efficient solid acid catalysts, namely, SnO2, WO3/SnO2, MoO3/SnO2, and SO42–/SnO2 for the production of bioadditive fuels from bioglycerol under ecofriendly conditions. The synthesized samples were meticulously analyzed by means of X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller (BET) surface area, Barrett–Joyner–Halenda pore size distribution, Fourier transform infrared (FT-IR) spectroscopy, FT-IR analysis of adsorbed pyridine, NH3-temperature programmed desorption, and other techniques. The catalytic efficiency of these solid acids was investigated for esterification and acetalization of glycerol with acetic acid and benzaldehyde, respectively. Characterization studies revealed that the textural properties (crystallite size and BET surface area) of pristine SnO2 were outstand...

Alcohol-related dementia: an update of the evidence

The characteristics of dementia relating to excessive alcohol use have received increased research interest in recent times. In this paper, the neuropathology, nosology, epidemiology, clinical features, and neuropsychology of alcohol-related dementia (ARD) and alcohol-induced persisting amnestic syndrome (Wernicke-Korsakoff syndrome, or WKS) are reviewed. Neuropathological and imaging studies suggest that excessive and prolonged use of alcohol may lead to structural and functional damage that is permanent in nature; however, there is debate about the relative contributions of the direct toxic effect of alcohol (neurotoxicity hypothesis), and the impact of thiamine deficiency, to lasting damage. Investigation of alcohol-related cognitive impairment has been further complicated by differing definitions of patterns of alcohol use and associated lifestyle factors related to the abuse of alcohol. Present diagnostic systems identify two main syndromes of alcohol-related cognitive impairment: ARD and WKS. However, 'alcohol-related brain damage' is increasingly used as an umbrella term to encompass the heterogeneity of these disorders. It is unclear what level of drinking may pose a risk for the development of brain damage or, in fact, whether lower levels of alcohol may protect against other forms of dementia. Epidemiological studies suggest that individuals with ARD typically have a younger age of onset than those with other forms of dementia, are more likely to be male, and often are socially isolated. The cognitive profile of ARD appears to involve both cortical and subcortical pathology, and deficits are most frequently observed on tasks of visuospatial function as well as memory and higher-order (executive) tasks. The WKS appears more heterogeneous in nature than originally documented, and deficits on executive tasks commonly are reported in conjunction with characteristic memory deficits. Individuals with alcohol-related disorders have the potential to at least partially recover - both structurally and functionally - if abstinence is maintained. In this review, considerations in a clinical setting and recommendations for diagnosis and management are discussed.

An overview of in silico protein function prediction

As the protein databases continue to expand at an exponential rate, fed by daily uploads from multiple large scale genomic and metagenomic projects, the problem of assigning a function to each new protein has become the focus of significant research interest in recent times. Herein, we review the most recent advances in the field of automated function prediction (AFP). We begin by defining what is meant by biological "function" and the means of describing such functions using standardised machine readable ontologies. We then focus on the various function-prediction programs available, both sequence and structure based, and outline their associated strengths and weaknesses. Finally, we conclude with a brief overview of the future challenges and outstanding questions in the field, which still remain unanswered.

Lamarckian memetic algorithms: local optimum and connectivity structure analysis

Memetic algorithms (MAs) represent an emerging field that has attracted increasing research interest in recent times. Despite the popularity of the field, we remain to know rather little of the search mechanisms of MAs. Given the limited progress made on revealing the intrinsic properties of some commonly used complex benchmark problems and working mechanisms of Lamarckian memetic algorithms in general non-linear programming, we introduce in this work for the first time the concepts of local optimum structure and generalize the notion of neighborhood to connectivity structure for analysis of MAs. Based on the two proposed concepts, we analyze the solution quality and computational efficiency of the core search operators in Lamarckian memetic algorithms. Subsequently, the structure of local optimums of a few representative and complex benchmark problems is studied to reveal the effects of individual learning on fitness landscape and to gain clues into the success or failure of MAs. The connectivity structure of local optimum for different memes or individual learning procedures in Lamarckian MAs on the benchmark problems is also investigated to understand the effects of choice of memes in MA design.