Metal Nanoparticles/Nanowires Selfassembly on Ripple Patterned Substrate - Mechanism, Properties and Applications

Plasmonic properties of self-assembled silver nanoparticles/nanowires array on periodically patterned Si (100) substrate are reported with special attention on the mechanism of nanoparticles self-assembly. The advantage of this bottom up approach over other self-assembling and lithographic methods is the flexibility to tune array periodicity down to 20 nm with interparticle gaps as low as 5 nm along the ripple. Ripple pattern have shallow modulation (~2 nm) still particles self-assembly was observed in non-shadow deposition. Therefore adatoms diffusion and kinetics is important on ripple surface for the self-assembly. PVD e-beam evaporation method used for deposition has proven to be superior to sputter deposition due to lower incident flux and lower atom energy. It was found that particles self-assembly largely dependent on angle of incidence, substrate temperature, and deposition direction due to ripple asymmetric tilt. Ostwald ripening observed during annealing on ripples substrate has striking dependency on ripple periodicity and was found to be different compared to Ostwald ripening on flat Si surface. In-situ RBS measurements of deposited silver on flat and rippled substrate confirmed different sticking of atoms on the two surfaces. The difference between maximum and minimum of the calculated local flux show a peak at an incidence angle of 70o with respect to surface normal. This explains the best alignment of particles at this angle of incidence compare to others. Self-assembled nanoparticles are optically anisotropic, i.e. they exhibit a direction dependent shift in LSPR. The reason of the observed anisotropy is a direction dependent plasmonic coupling. Different in plane and out of the plane dielectric coefficients calculated by modelling Jones matrix elements, confirms that nanoparticle/nanowire array are biaxial anisotropic (ex ¹ ey ¹ ez). The nanoparticles are predominantly insulating while nanowires are both metallic and insulating depending on the dimension. Silver nanoparticles/nanowires self-aligned on pre-patterned rippled substrate are presented for the first time as an active SERS substrate. Anisotropic SERS response in such arrays is attributed to different field enhancement along and across the ripples. Strong plasmonic coupling in elongated nanoparticles chain results in significantly higher SERS intensity then spherical nanoparticles/nanowires and non-ordered nanoparticles. Higher SERS intensity across the nanowires array in comparison to along the array (bulk silver) confirms electromagnetic field enhancement (hot-junction) is responsible for SERS phenomenon. Self-assembly of cobalt nanoparticle on ripple pattern substrate is also reported. Due to less adatom mobility and higher sticking cobalt self-assembly is possible only at much higher temperature. A strong uniaxial magnetic anisotropy was observed not observed for non ordered cobalt particles

Metal Nanoparticles/Nanowires Self-assembly on Ripple Patterned Substrate: Mechanism, properties, and applications

Plasmonic properties of self-assembled silver nanoparticles/nanowires array on periodically patterned Si (100) substrate are reported with special attention on the mechanism of nanoparticles self-assembly. The advantage of this bottom up approach over other self-assembling and lithographic methods is the flexibility to tune array periodicity down to 20 nm with interparticle gaps as low as 5 nm along the ripple. Ripple pattern have shallow modulation (~2 nm) still particles self-assembly was observed in non-shadow deposition. Therefore adatoms diffusion and kinetics is important on ripple surface for the self-assembly. PVD e-beam evaporation method used for deposition has proven to be superior to sputter deposition due to lower incident flux and lower atom energy. It was found that particles self-assembly largely dependent on angle of incidence, substrate temperature, and deposition direction due to ripple asymmetric tilt. Ostwald ripening observed during annealing on ripples substrate has striking dependency on ripple periodicity and was found to be different compared to Ostwald ripening on flat Si surface. In-situ RBS measurements of deposited silver on flat and rippled substrate confirmed different sticking of atoms on the two surfaces. The difference between maximum and minimum of the calculated local flux show a peak at an incidence angle of 70o with respect to surface normal. This explains the best alignment of particles at this angle of incidence compare to others. Self-assembled nanoparticles are optically anisotropic, i.e. they exhibit a direction dependent shift in LSPR. The reason of the observed anisotropy is a direction dependent plasmonic coupling. Different in plane and out of the plane dielectric coefficients calculated by modelling Jones matrix elements, confirms that nanoparticle/nanowire array are biaxial anisotropic (ex ¹ ey ¹ ez). The nanoparticles are predominantlyinsulating while nanowires are both metallic and insulating depending on the dimension. Silver nanoparticles/nanowires self-aligned on pre-patterned rippled substrate are presented for the first time as an active SERS substrate. Anisotropic SERS response in such arrays is attributed to different field enhancement along and across the ripples. Strong plasmonic coupling in elongated nanoparticles chain results in significantly higher SERS intensity then spherical nanoparticles/nanowires and non-ordered nanoparticles. Higher SERS intensity across the nanowires array in comparison to along the array (bulk silver) confirms electromagnetic field enhancement (hot-junction) is responsible for SERS phenomenon. Self-assembly of cobalt nanoparticle on ripple pattern substrate is also reported. Due to less adatom mobility and higher sticking cobalt self-assembly is possible only at much higher temperature. A strong uniaxial magnetic anisotropy was observed not observed for non ordered cobalt particles

Death clustering in India: Levels, trends, and differentials, 1992–2016

Background: India and many of its bigger states could not achieve the national goal related with child health based on 4th UN Millennium Development Goal. There is a need to look for different approaches which deal with infant mortality. Literature emphasizes clustering of infant deaths in families has implications on infant mortality. Objective: The present study attempts to examine the levels, trends, and differentials of clustering of infant deaths in families in India using National Family Health Survey (NFHS) dataset and how they changed over the years. Materials and Methods: Study used bivariate analysis and multilevel random effects logit model based intraclass correlation coefficient and median odds ratio to examine the clustering of deaths in families, in India. Results: There has been a consistent decline in both infant mortality rate (IMR) and clustering of infant deaths in families in India between 1992 and 2016. However, the pace of decline was faster after 2005. States such as Uttar Pradesh, Madhya Pradesh, and Bihar are the major contributors in clustering of infant deaths in families. In Kerala, clustering of infant deaths has been disappeared in families while among relatively more developed states such as Maharashtra and Tamil Nadu have experienced a reduction in clustering of infant deaths in families by an amount of <1%. Conclusion: Between NFHS-3 and NFHS-4 there has been an increase in clustering of infant deaths among mothers with age at first birth >30 years and for mothers who have received higher education. IMR can be reduced to a greater extent if government policies and health resources are directed toward the families experiencing the clustering of infant deaths

Controlling the size distribution of nanoparticles through the use of physical boundaries during laser ablation in liquids

A simple, yet effective method of controlling the size and size distributions of nanoparticles produced as a result of laser ablation of target material is presented. The method employs the presence of physical boundaries on either sides of the ablation site. In order to demonstrate the potential of the method, experiments have been conducted with copper and titanium as the target materials that are placed in two different liquid media (water and isopropyl alcohol). The ablation of the target material immersed in the liquid medium has been carried out using an Nd:YAG laser. Significant differences in the size and size distributions are observed in the cases of nanoparticles produced with and without confining boundaries. It is seen that for any given liquid medium and the target material, the mean size of the nanoparticles obtained with the boundary-fitted target surface is consistently higher than that achieved in the case of open (flat) targets. The observed trend has been attributed to the plausible role(s) of the confining boundaries in prolonging the thermalisation time of the plasma plume. In order to ascertain that the observed differences in sizes of the nanoparticles produced with and without the presence of the physical barriers are predominantly because of the prolonged thermalisation of the plasma plume and not due to the possible formation of oxide layer, select experiments with gold as the target material in water have also been performed. The experiments also show that, irrespective of the liquid medium, the increase in the mean size of the copper-based nanoparticles due to the presence of physical boundaries is relatively higher than that observed in the case of titanium target material under similar experimental conditions.Comment: 24 pages, 9 figures, a part of this work has been published in Photonics Prague 2017, (Proc. SPIE 10603, Photonics, Devices, and Systems VII, 1060304) titled "A novel method for fabrication of size-controlled metallic nanoparticles

Determinants and differentials of postpartum amenorrhea associated with breastfeeding among women in Bihar, India

Background: Postpartum amenorrhea is considered to be the conception variable and its affect natural fertility by    lengthening the inter-live birth interval. In societies where the fertility is not regulated through the use of contraception method there amenorrhea period can exert a dominant fertility inhibiting effect on fertility. In this paper we check differentials in duration of breastfeeding and Postpartum Amenorrhea (PPA), and to estimate mean duration of Postpartum Amenorrhea (PPA) associated with breastfeeding with influence of Scio-economic and demographic factors of ever-married woman who had given at least one but last birth in Bihar, India.Methods: Kaplan Meier Survival method use to estimate the duration of breastfeeding and postpartum amenorrhea and multivariate Cox proportional hazard model used to measure the effect of each category of each variable on the hazard function while controlling for the effects of other variables (and their categories) included in the model.Results: Duration of breastfeeding, parity, residence, contraceptive use have a significant impact on duration of postpartum amenorrhea (PPA) and empirical evidence indicates that longer and more frequent breastfeeding may increase the length of an ovulatory period. Mothers with a BMI greater than 18.5 kg/m2 resume ovulation faster and high mean for duration of breastfeeding than those with a lower BMI.Conclusions: Parity, age of mothers, survival status of child and socio-economic status of mothers are found to be the main influencing factors for the timing of postpartum amenorrhea and also duration of breastfeeding among mothers., it is expected that the findings may help in designing appropriate policies and programs for improving mothers' and children's health as well as for reducing the existing fertility level of a region where contraceptive practices is low

Clustering of child deaths among families in low- and middle-income countries: a meta-analysis

BACKGROUND AND AIMS: Several studies have examined the phenomenon of "death clustering," in which two or more children born to the same mother or from the same family die at an early age. Therefore, a scientific examination of the results is essential to understand how the survival status of the older siblings affects the survival of the younger siblings. By using meta-analysis, this study aims to provide a quantitative synthesis of the results of studies on "child death clustering" in low- and middle-income countries (LMICs). METHODS: This study followed the PRISMA-P 2015 guidelines. We used four electronic databases-PubMed, Medline, Scopus, and Google Scholar with search and citation analysis capabilities. Initially, 140 studies were identified, but only 27 met the eligibility criteria eventually. These were studies that had used the death of a previous child as a covariate to determine the survival status of the index child. The heterogeneity and the publication bias of the studies were examined using the Cochran test, I 2 statistic, and Egger's meta-regression test. RESULTS: The pooled estimate of 114 study estimates for LMICs contains some bias. India's 37 study estimates were distributed more or less equally along the middle line, indicating no publication bias, while there was a slight bias in the estimates for Africa, Latin America, and Bangladesh. The odds of experiencing the death of the index child in the selected LMICs were 2.3 times higher for mothers who had lost any prior child as compared to those mothers who had not had any prior child loss. For African mothers, the odds were five times higher, whereas for Indian mothers, the odds were 1.66 times higher. Mothers' characteristics, such as education, occupation, health-seeking behavior, and maternal competence, significantly affect the child's survival status. CONCLUSION: Achieving the sustainable development goals would not be possible if mothers in countries experiencing high levels of under-five mortality are not provided with better health and nutrition facilities. Mothers who have lost multiple children should be targeted for assistance

Omental infarction: A rare cause of acute abdomen

Omental infarction is an uncommon but important cause of acute abdominal pain, which frequently mimics other surgical presentations. Low incidence and non-specific presentation contribute to Omental infarction being misconstrued for appendicitis, peptic ulcer perforation, acute pancreatitis or mesenteric ischemia. Its etiology remains uncertain, predisposing factors include obesity, strenuous activity, trauma, and sometimes idiopathic. Its diagnosis has traditionally been one of exclusion, based on intraoperative and pathologic findings. Here, we report the case of idiopathic omental infarction in a 51-year-old male. We discuss the diagnosis of primary omental infarction as well as the role of conservative and surgical management

Sub-monolayer growth of Ag on flat and nanorippled SiO2 surfaces

In-situ Rutherford Backscattering Spectrometry (RBS) and Molecular Dynamics (MD) simulations have been used to investigate the growth dynamics of silver on a flat and the rippled silica surface. The calculated sticking coeficient of silver over a range of incidence angles shows a similar behaviour to the experimental results for an average surface binding energy of a silver adatom of 0.2 eV. This value was used to parameterise the MD model of the cumulative deposition of silver in order to understand the growth mechanisms. Both the model and the RBS results show marginal difference between the atomic concentration of silver on the at and the rippled silica surface, for the same growth conditions. For oblique incidence, cluster growth occurs mainly on the leading edge of the rippled structure