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The Indian Pulsar Timing Array (InPTA) employs unique features of the upgraded Giant Metrewave Radio Telescope (uGMRT) to monitor dozens of the International Pulsar Timing Array (IPTA) millisecond pulsars (MSPs), simultaneously in the 300-500 MHz and the 1260-1460 MHz bands. This dual-band approach ensures that any frequency-dependent delays are accurately characterized, significantly improving the timing precision for pulsar observations, which is crucial for pulsar timing arrays. We present details of InPTA’s second data release that involves 7 yrs of data on 27 IPTA MSPs. This includes sub-banded Times of Arrival (ToAs), Dispersion Measures (DM), and initial timing ephemerides for our MSPs. A part of this dataset, originally released in InPTA’s first data release, is being incorporated into IPTA’s third data release which is expected to detect and characterize nanohertz gravitational waves in the coming years. The entire dataset is reprocessed in this second data release providing some of the highest precision DM estimates so far and interesting solar wind related DM variations in some pulsars. This is likely to characterize the noise introduced by the dynamic inter-stellar ionised medium much better than the previous release thereby increasing sensitivity to any future gravitational wave search.
Exploration expeditions were conducted for 2 consecutive years in the subtropical region of North India to collect the untapped genetic diversity of Bael. A total of 15 accessions having unique traits of horticultural importance were collected and conserved in the field gene bank. Conserved germplasm was characterized for 3 consecutive years. Considerable variability was found in the morphological characters and biochemical traits. Fruit length ranged from 10.15 to 17. 68 cm, fruit circumference varied from 33.45 to 56.32 cm and fruit weight varied from 0.71 to 2.48 kg. Shell thickness was found to vary from 2.11 to 3.62 mm, whereas shell weight varied from 230 to 580 g/fruit. Number of seed sacs per fruit was found to vary from 11.17 to 15.72 and number of seeds per fruit varied from 68.00 to 113.17. Minimum seed weight was 7.04 g/fruit, whereas maximum 14.55 g/fruit. Ample variability was found in fruit yield of collected germplasm which ranged from 18.85 to 39.26 kg per plant at 16–18 years of age. Distinctive variability in biochemical traits was also found. Total soluble solids in fruit pulp were 34.92–41.13% Brix, total sugars 11.49–22.16%, acidity 0.36–0.53%, vitamin ‘C’ 9.89–17.20 mg/100 g, total carotenoids 1.43–2.40 mg/100 g and total tannins 2.50–3.58%. Available genetic diversity may be utilized for crop improvement programme.
Sustainability of maize production systems is threatened by poor economic returns and resource intensiveness. Therefore, an experiment was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi during 2016–17 to 2017–18 to assess the effect of tillage and microbial inoculantsintegrated phosphorus (P) management on productivity, quality, economic outcome and energy dynamics of maize. Three tillage practices viz., CT–R (conventional tillage with no residue), ZT–R (zero tillage with no residue) and ZT + R (zero tillage with wheat crop residue at 2.5 Mg/ha) were assigned in main plots and five P management practices viz., P1 (control–NK as per recommendation, but no P), P2 (17.2 kg P/ha), P3 (17.2 kg P/ha + PSB), P4 (17.2 kg P/ha + compost inoculants) and P5 (34.4 kg P/ha) were allocated in subplots in three times replicated split-plot design. The maximum grain yield (5.96 Mg/ha), protein content (9.13%), protein yield (546 kg/ha) and gross energy returns (209 × 103 MJ/ha) were recorded under ZT + R while higher benefit: cost ratio (B: C ratio – the amount of economic gain per unit investment) (1.53) and energy efficiency (12.5) was noticed under ZT–R. Among the P management practices, the application of 34.4 kg P/ha recorded the highest grain yield (6.45 Mg/ha), protein content (9.34%), protein yield (603 kg/ha), B: C ratio (1.65) and energy efficiency (10.1). The results suggested that the application of P at the rate of 34.4 kg/ha under ZT + R is an economically robust approach for the quality maize production in semi-arid region.
Self-propelled flapping foils with distinct locomotion-enabling kinematic restraints exhibit a remarkably similar Strouhal number ($St$)-Reynolds number ($Re$) dependence. This similarity has been hypothesized to pervade diverse forms of oscillatory self-propulsion and undulatory biolocomotion; however, its genesis and implications on the energetic cost of locomotion remain elusive. Here, using high-resolution simulations of translationally free and restrained foils that self-propel as they are pitched, we demonstrate that a generality in the $St$-$Re$ relationship can emerge despite significant disparities in thrust generation mechanics and locomotory performance. Specifically, owing to a recoil reaction induced passive heave, the fluid's inertial response to the prescribed rotational pitch, the principal source of thrust in unidirectionally free and towed configurations, ceases to produce thrust in a bidirectionally free configuration. Rather, the thrust generated from the leading edge suction mechanics self-propels a bidirectionally free pitching foil. Owing to the foregoing distinction in the thrust generation mechanics, the $St$-$Re$ relationships for the bidirectionally and unidirectionally free/towed foils are dissimilar and pitching amplitude dependent, but specifically for large reduced frequencies, converge to a previously reported unified power law. Importantly, to propel at a given mean forward speed, the bidirectionally free foil must counteract the out-of-phase passive heave through a more intense rotational pitch, resulting in an appreciably higher power consumption over the range $10 \leq Re \leq 10^3$. We highlight the critical role of thrust in introducing an offset in the $St$-$Re$ relation, and through its amplification, being ultimately responsible for the considerable disparity in the locomotory performance of differentially constrained foils.
Every year in the month of September, National Suicide Prevention Week is celebrated. The goal of suicide prevention week is to inform the public about suicide prevention, primarily the warning signs of suicide. However, the impact of this month on the general population is unknown. The Google trends show how frequent web searches have been performed for a particular search-term, which provide an approximation of the people’s interest.
Objectives
To evaluate public interest in suicide prevention by analyzing the google trends of “Suicide Prevention” search-term.
Methods
We estimated the interest in such topics by running the google trends data of the last decade by using the filter [Search Term:“Suicide Prevention”, Locations: “United States” and Time Ranges “ 2010 to 2020”].
Results
During this specific interval, people have searched “Suicide Prevention” most frequently during the month of September (month of National Suicide Prevention week). Conversely, in the other months, interest in “suicide prevention” fluctuated between little to none. The only other time people have shown interest in Suicide prevention, other than the month of September, was with suicide news in the media, such as the death of a celebrity by suicide, or suicide-related TV shows. [Figure]
Conclusions
Although it is not definitive, it gives some idea that National Suicide Prevention week has a considerable impact on population interest. Since we did not observe sufficient public interest in other months, there should be frequent and systematic efforts to spread suicide prevention awareness among the general population.
We present an asymptotic theory for analytical characterization of the high-Reynolds-number incompressible flow of a Newtonian fluid past a shear-free circular cylinder. The viscosity-induced modifications to this flow are localized and except in the neighbourhood of the rear stagnation point, behave like a linear perturbation of the inviscid flow. Our theory gives a highly accurate description of these modifications by including the contribution from the most significant viscous term in a correctional perturbation expansion about an inviscid base state. We derive the boundary layer equation for the flow and deduce a similarity transformation that leads to a set of infinite, shear-free-condition-incompatible, self-similar solutions. By suitably combining members from this set, we construct an all-boundary-condition-compatible solution to the boundary layer equation. We derive the governing equation for vorticity transport through the narrow wake region and determine its closed-form solution. The near and far-field forms of our wake solution are desirably consistent with the boundary layer solution and the well-known, self-similar planar wake solution, respectively. We analyse the flow in the rear stagnation region by formulating an elliptic partial integro-differential equation for the distortion streamfunction that specifically accounts for the fully nonlinear and inviscid dynamics of the viscous correctional terms. The drag force and its atypical logarithmic dependence on Reynolds number, deduced from our matched asymptotic analysis, are in remarkable agreement with the high-resolution simulation results. The logarithmic dependence gives rise to a critical Reynolds number below which the viscous correction term, counterintuitively, reduces the net dissipation in the flow field.
Despite persistent efforts, unmet need for contraceptives in India has declined only slightly from 14% to 13% between 2005–06 and 2015–16. Many women using a family planning method discontinue it without switching to another method and continue to have unmet need. This study quantified the share of current unmet need for modern contraceptive methods attributed to past users of these methods in India. Data were drawn from two rounds of the National Family Health Survey conducted in 2005–06 and 2015–16. Using information on women with current unmet need, and whether they used any modern method in the past, the share of past users with current unmet need for modern methods was calculated. Bivariate and multivariate analyses were performed. Among 46 million women with unmet need, 11 million were past users of modern methods in 2015–16. The share of current unmet need attributed to past users of modern contraceptive methods declined from 27% in 2005–06 to 24% in 2015–16. Share of current unmet need attributed to past users was associated with reversible method use. This share rose with increased use of modern reversible methods. With the Indian family planning programme’s focus on increasing modern reversible method use, the share of unmet need attributed to past users of modern methods is likely to increase in the future. The programme’s emphasis on continuation of contraceptive use, along with bringing in new users, could be one of the key strategies for India to achieve the FP2020 goals.
Pharmacogenetic studies in obsessive-compulsive disorder (OCD) primarily focussing on serotonergic and dopaminergic polymorphisms, provided inconsistent findings. There is recent evidence for glutamatergic abnormalities in OCD.
Aims
Examine the association glutamatergic genes with serotonin reuptake inhibitor (SRI) response in OCD.
Objectives
To study pharmacogenetic association between SLC1A1 and GRIN2B polymorphisms with SRI response in OCD.
Methods
DSM-IV OCD patients were recruited from a specialty OCD clinic and evaluated using the Yale-Brown obsessive compulsive scale (YBOCS), Mini International Neuropsychiatric Interview (MINI) plus, Clinical Global Impression scale (CGI). They were subsequently reassessed with YBOCS and CGI. To study extreme phenotypes, we included only full responders (> 35% YBOCS improvement and CGI-I score of 1 or 2) to any SRI (n = 191) and non-responders (< 25% YBOCS improvement and CGI-I score ≥ 4) to adequate trial of at least two SRIs (n = 84). Partial responders were excluded. Genotyping was performed using an ABI9700 PCR machine.
Results
Genotype frequencies did not deviate significantly from the values predicted by the Hardy-Weinberg equation. Case-control association analyses revealed no significant association between genotype/allele frequencies with SRI response.
Conclusion
Our data does not show any association between polymorphisms in glutamatergic genes and SRI response in OCD though such associations have been found in other studies. More SNP's in the same gene could be responsible for the pharmacogenetic associations. More homogenous sample considering symptom dimensions and other phenotypic variables may be needed. It may be critical to go beyond “usual suspect” candidate gene research. In this regard, a novel approach to identify SRI response biomarkers is the use of cellular models.
Disclosure of interest
The authors have not supplied their declaration of competing interest.
In this paper, we present and implement a novel approach for position-based visual servoing. The challenge of controlling the mobile robot while simultaneously estimating the camera to mobile robot transformation is solved. This is achieved using gradient descent (GD)-based estimation and the sliding-mode approach. The GD approach allows online parameter estimation for controlling the robot to achieve a desired position and orientation. The adaptive nature of the parameters demonstrates the robustness of the system. In contrast to existing work, the proposed technique achieves both estimation and control tasks in a single experiment. Simulation and experimental results are provided to validate the performance of the proposed scheme.
In preparation for a multisite antibiotic stewardship intervention, we assessed knowledge and attitudes toward management of asymptomatic bacteriuria (ASB) plus teamwork and safety climate among providers, nurses, and clinical nurse assistants (CNAs).
Design:
Prospective surveys during January–June 2018.
Setting:
All acute and long-term care units of 4 Veterans’ Affairs facilities.
Methods:
The survey instrument included 2 previously tested subcomponents: the Kicking CAUTI survey (ASB knowledge and attitudes) and the Safety Attitudes Questionnaire (SAQ).
Results:
A total of 534 surveys were completed, with an overall response rate of 65%. Cognitive biases impacting management of ASB were identified. For example, providers presented with a case scenario of an asymptomatic patient with a positive urine culture were more likely to give antibiotics if the organism was resistant to antibiotics. Additionally, more than 80% of both nurses and CNAs indicated that foul smell is an appropriate indication for a urine culture. We found significant interprofessional differences in teamwork and safety climate (defined as attitudes about issues relevant to patient safety), with CNAs having highest scores and resident physicians having the lowest scores on self-reported perceptions of teamwork and safety climates (P < .001). Among providers, higher safety-climate scores were significantly associated with appropriate risk perceptions related to ASB, whereas social norms concerning ASB management were correlated with higher teamwork climate ratings.
Conclusions:
Our survey revealed substantial misunderstanding regarding management of ASB among providers, nurses, and CNAs. Educating and empowering these professionals to discourage unnecessary urine culturing and inappropriate antibiotic use will be key components of antibiotic stewardship efforts.
This study examined the pattern of economic disparity in the modern contraceptive prevalence rate (mCPR) among women receiving contraceptives from the public and private health sectors in India, using data from all four rounds of the National Family Health Survey conducted between 1992–93 and 2015–16. The mCPR was measured for currently married women aged 15–49 years. A concentration index was calculated and a pooled binary logistic regression analysis conducted to assess economic disparity (by household wealth quintiles) in modern contraceptive use between the public and private health sectors. The analyses were stratified by rural–urban place of residence. The results indicated that mCPR had increased in India over time. However, in 2015–16 only half of women – 48% (33% from the public sector, 12% from the private sector, 3% from other sources) – were using any modern contraceptive in India. Over time, the economic disparity in modern contraceptive use reduced across both public and private health sectors. However, the extent of the disparity was greater when women obtained the services from the private sector: the value of the concentration index for mCPR was 0.429 when obtained from the private sector and 0.133 when from the public sector in 2015–16. Multivariate analysis confirmed a similar pattern of the economic disparity across public and private sectors. Economic disparity in the mCPR has reduced considerably in India. While the economic disparity in 2015–16 was minimal among those accessing contraceptives from the public sector, it continued to exist among those receiving services from the private sector. While taking appropriate steps to plan and monitor private sector services for family planning, continued and increased engagement of public providers in the family planning programme in India is required to further reduce the economic disparity among those accessing contraceptive services from the private sector.
The staurolite-bearing schists of the area were metamorphosed in the staurolite-kyanite zone of the amphibolite facies. The various assemblages of the pelitic schists are represented in the AKF and Thompson's AFM diagrams. Within the PT conditions of stability of staurolite, this mineral develops in pelitic schists that have a high Al2O3 (excess)/(K2O+FeO+MgO) ratio so that the plots of analyses lie above the muscovite-garnet join in the AKF diagram. The three-phase field of staurolite-kyanite-biotite in the AFM diagram migrates towards the lower FeO/MgO side with increasing oxidation ratio and thus staurolite-bearing rocks are not necessarily restricted to pelitic schists with high FeO/MgO ratio as is commonly believed. On the other hand, the three-phase field shifts towards the higher FeO/MgO side with increasing grade of metamorphism assuming oxidation ratio and pressure to be constant, thus reducing the composition field of staurolite schists in the AFM diagram.
Geomorphic analysis and optically stimulated luminescence (OSL) ages from undated Lake Agassiz beaches and adjacent fluvial sediments on Riding Mountain in Manitoba provide insight into their early history. New OSL ages of 14.5±2.4 and 13.4±0.7 ka on the oldest (Herman to Norcross) beaches of Lake Agassiz near the Canada-U.S. border indicate that the Laurentide Ice Sheet (LIS) retreated from that part of the Agassiz basin by ~14.5 ka. To the north along Riding Mountain, the Herman strandlines are absent, and OSL ages on the oldest beach there average 12.9 ka, which links it to the younger Norcross-Tintah strandlines. In adjacent Riding Mountain, OSL ages and geomorphological relationships of a large abandoned glacial spillway >200 m above the oldest beaches of Lake Agassiz indicate that this channel predates retreat of the LIS and formation of beaches in this part of the Agassiz basin, with ice remaining in this area until after 14.5 ka. OSL ages on the Gimli beach 170 km to the east are >3000 yr older than conventional assignments, suggesting that it formed during the Moorhead low-water phase 12.8–10.6 ka. Luminescence ages support the conclusion that the Campbell beach formed ~10.9 ka near the end of the Moorhead low-water phase.
Influenza A(H1N1) viruses of the 2009 pandemic (A(H1N1)pdm09) continue to cause outbreaks in the post-pandemic period. During January to May 2015, an upsurge of influenza was recorded that resulted in high fatality in central India. Genetic lineage, mutations in the hemagglutinin (HA) gene and infection by quasi-species are reported to affect disease severity. The objective of this study is to present the molecular and epidemiological trends during the 2015 influenza outbreak in central India. All the referred samples were subjected to qRT–PCR for diagnosis. HA gene sequencing (23 survivors and 24 non-survivors) and cloning were performed and analyzed using Molecular Evolutionary Genomic Analyzer (MEGA 5·05). Of the 3625 tested samples, 1607 (44·3%) were positive for influenza A(H1N1)pdm09, of which 228 (14·2%) individuals succumbed to death. A significant trend was observed in positivity (P = 0·003) and mortality (P < 0·0001) with increasing age. The circulating A(H1N1)pdm09 virus was characterized as belonging to clade-6B. Clinically significant mutations were detected. Patients infected with the quasi-species of the virus had a greater risk of death (P = 0·009). This study proposes a robust molecular and clinical surveillance program for the detection and characterization of the virus, along with prompt treatment protocols to prevent outbreaks.
Studies suggest that disturbance-induced reductions in soil seedbank density are diminished by periods of water scarcity after soil disturbance; however, this hypothesis has yet to be tested. The objectives of this study were (1) to determine the effects of increasing time between soil disturbance and flood irrigation on disturbance-induced reductions in soil seedbank density, and (2) to identify specific soil moisture levels that cause seedbank reductions under flood irrigation. Weed species in this study were junglerice, Palmer amaranth, and yellow foxtail. For Objective 1, artificial seedbanks with known numbers of seeds were disturbed 10, 3, or 0 d prior to flood irrigations under field conditions. For Objective 2, seeds were buried in soil mesocosms that were hydrated to specific soil water potentials (flooded, 0 kPa, −30 kPa, −60 kPa, and −180 kPa) and placed in laboratory conditions favorable for germination. For both objectives, seeds were recovered to determine the percentages of buried seeds that survived the disturbance or moisture treatments. Results for the field study indicated that soil disturbances reduced seedbank persistence of Palmer amaranth but did not affect seedbank persistence of junglerice and yellow foxtail. Disturbance-induced reductions in seedbank density were greatest when soil was disturbed 0 and 3 d prior to flood irrigations. For the laboratory study, results showed that waterlogged soil was not required for seedbank losses because rates of seedbank persistence were greater in saturated soils (0 kPa and flooded) compared to the lower moisture levels. These studies indicate that delays in irrigation can reduce the seedbank reduction potentials of soil disturbance events. Further, irrigation timing effects on disturbed soil seedbanks are likely to occur in all irrigation systems, including those that reduce the amount of water applied compared to flood irrigation.
We perform a comprehensive characterization of the propulsive performance of a thrust generating pitching foil over a wide range of Reynolds ($10\leqslant Re\leqslant 2000$) and Strouhal ($St$) numbers using a high-resolution viscous vortex particle method. For a given $Re$, we show that the mean thrust coefficient $\overline{C_{T}}$ increases monotonically with $St$, exhibiting a sharp rise as the location of the inception of the wake asymmetry shifts towards the trailing edge. As a result, the propulsive efficiency too rises steeply before attaining a maximum and eventually declining at an asymptotic rate that is consistent with the inertial scalings of $St^{2}$ for $\overline{C_{T}}$ and $St^{3}$ for the mean power coefficient, with the latter scaling holding, quite remarkably, over the entire range of $Re$. We find the existence of a sharp increase in the peak propulsive efficiency ${\it\eta}_{max}$ (at a given $Re$) in the $Re$ range of 50 to approximately 1000, with ${\it\eta}_{max}$ increasing rapidly from about 1.7 % to the saturated asymptotic value of approximately $16\,\%$. The $St$ at which ${\it\eta}_{max}$ is attained decreases progressively with $Re$ towards an asymptotic limit of $0.45$ and always exceeds the one for transition from a reverse von Kármán to a deflected wake. Moreover, the drag-to-thrust transition occurs at a Strouhal number $St_{tr}$ that exceeds the one for von Kármán to reverse von Kármán transition. The $St_{tr}$ and the corresponding power coefficient $\overline{C_{p,}}_{tr}$ are found to be remarkably consistent with the simple scaling relationships $St_{tr}\sim Re^{-0.37}$ and $\overline{C_{p,}}_{tr}\sim Re^{-1.12}$ that are derived from a balance of the thrust generated from the pitching motion and the drag force arising out of viscous resistance to the foil motion. The fact that the peak propulsive efficiency degrades appreciably only below $Re\approx 10^{3}$ establishes a sharp lower threshold for energetically efficient thrust generation from a pitching foil. Our findings should be generalizable to other thrust-producing flapping foil configurations and should aid in establishing the link between wake patterns and energetic cost of thrust production in similar systems.
The discovery of graphene based materials has led to significant advancement in several different areas. The large surface area, nanoporous structure and availability of delocalized electron network provide a unique opportunity for purification of solvents via adsorption, absorption or simple trapping. This makes graphene based materials as potential candidates for purification and desalination of water. Here we report synthesis of 3D porous network of oxidized graphene for purification of sea water. The membranes fabricated using these frameworks are hierarchically linked intrinsically defected oxidised graphene sheets by long micro-channels and capable of filtering small ions such as Na+ and Cl-. These are easy to fabricate, reusable and economically viable especially for point of use application. We finally show a fabricated device using membrane made from these 3D networks of oxidized graphene.
Various promising applications such as acoustic cloaking, sub-wavelength imaging, acoustic wave manipulation, transmission or reflection control etc. are feasible because of the ability of manipulating sounds and vibrations using artificially engineered “Acoustics meta-materials”. Recent works on space-coiling acoustic metamaterials show their extreme constitutive parameters like large refractive index, double negativity and zero mass density. Three dimensional structures have a wide application in sub-wavelength broadband acoustic wave suppression due to huge attenuation. Here we report the study of propagated and transmitted wave through 3D acoustic metamaterials structure using finite element method. Our simulations on 3D structure show a huge absorption/damping over few hundreds kilohertz frequency range.
Dengue is regarded as the most important arboviral disease. Although sporadic cases have been reported, serotypes responsible for outbreaks have not been identified from central India over the last 20 years. We investigated two outbreaks of febrile illness, in August and November 2012, from Korea district (Chhattisgarh) and Narsinghpur district (Madhya Pradesh), respectively. Fever and entomological surveys were conducted in the affected regions. Molecular and serological tests were conducted on collected serum samples. Dengue-specific amplicons were sequenced and phylogenetic analyses were performed. In Korea and Narsinghpur districts 37·3% and 59% of cases were positive, respectively, for dengue infection, with adults being the worst affected. RT–PCR confirmed dengue virus serotype 1 genotype III as the aetiology. Ninety-six percent of infections were primary. This is the first time that dengue virus 1 outbreaks have been documented from central India. Introduction of the virus into the population and a conducive mosquitogenic environment favouring increased vector density caused the outbreak. Timely diagnosis and strengthening vector control measures are essential to avoid future outbreaks.
Man Mohan, Emeritus Professor, Department of Physics and Astrophysics, University of Delhi, Delhi,Anil Kumar Maini, Former Director, Laser Science and Technology Centre, Delhi,Aranya B. Bhattacherjee, Associate Professor, Department of Physics, ARSD College, University of Delhi, Delhi
Silicon, the second most abundant element (after oxygen) in the earth's crust, making up 25.7% of the crust by mass, is one of most (probably the absolute) striking material for electronic and technological applications. It has thus become the leading and most prominent building-block material for electronics. Silicon has an indirect band gap of 1.12 eV that is ideal for room temperature operation. It allows the processing flexibility to place today more than 109 devices on a single chip. However, all the single transistors and electronic devices have transferred information to length scale which is relevant with respect to their nanometric scale. Pushing down the dimension of silicon-based devices toward the nanometric scale determines a high concentration of transistors on a single silicon crystal (around 200 mm for the moment) that have permitted high integration level high-speed device performances and unprecedented interconnection levels.
Amorphous semiconductors represent an important area in materials science, which is interesting both from the technological and the theoretical point of view. The simplest way to describe the structure of an amorphous material like a disordered solid is short-range coordination. Extended atomic network of amorphous silicon (a-Si) is random[1]. In other words, the local coordination is tetrahedral (sp3 hybridization) as in crystalline Si (c-Si). The first nearest-neighbor distance, coordination number, or binding energy remains more or less same as in the amorphous and crystalline phases. Moreover, the covalent nature of the bonds means that short-range interactions play a prominent role. Density of electronic or vibrational states is similar in amorphous Si (a-Si) and c-Si[2, 3]. Semiconducting properties are also preserved in the a-Si. As a matter of fact, the presence of dangling bonds in the a-Si affects the performance of electronic devices. In practice, this can be circumvented by hydrogenation of the amorphous material, since hydrogen is a good terminator for insaturated bonds. From the theoretical point of view[2], the main features of the density of states can be accounted for by a molecular description (tight binding or valence force field models). Effect of the topological disorder mainly broadens linewidth of the Raman modes.
Semiconductor nanostructures have also been investigated in recent years due to their immense applications in electronic and optoelectronic devices[4, 5]. Electronic and optical properties of semiconductor nanostructures are strongly affected by the quantum confinement effect due to the reduced dimensions of these systems.