107 research outputs found
Suppression of the vacuum space-charge effect in fs-photoemission by a retarding electrostatic front lens
The performance of time-resolved photoemission experiments at fs-pulsed photon sources is ultimately limited by the eβe Coulomb interaction, downgrading energy and momentum resolution. Here, we present an approach to effectively suppress space-charge artifacts in momentum microscopes and photoemission microscopes. A retarding electrostatic field generated by a special objective lens repels slow electrons, retaining the k-image of the fast photoelectrons. The suppression of space-charge effects scales with the ratio of the photoelectron velocities of fast and slow electrons. Fields in the range from β20 to β1100 V/mm for Ekin = 100 eV to 4 keV direct secondaries and pump-induced slow electrons back to the sample surface. Ray tracing simulations reveal that this happens within the first 40 to 3 ΞΌm above the sample surface for Ekin = 100 eV to 4 keV. An optimized front-lens design allows switching between the conventional accelerating and the new retarding mode. Time-resolved experiments at Ekin = 107 eV using fs extreme ultraviolet probe pulses from the free-electron laser FLASH reveal that the width of the Fermi edge increases by just 30 meV at an incident pump fluence of 22 mJ/cm2 (retarding field β21 V/mm). For an accelerating field of +2 kV/mm and a pump fluence of only 5 mJ/cm2, it increases by 0.5 eV (pump wavelength 1030 nm). At the given conditions, the suppression mode permits increasing the slow-electron yield by three to four orders of magnitude. The feasibility of the method at high energies is demonstrated without a pump beam at Ekin = 3830 eV using hard x rays from the storage ring PETRA III. The approach opens up a previously inaccessible regime of pump fluences for photoemission experiments
Prevalence of Household-level Food Insecurity and Its Determinants in an Urban Resettlement Colony in North India
An adequate food intake, in terms of quantity and quality, is a key to
healthy life. Malnutrition is the most serious consequence of food
insecurity and has a multitude of health and economic implications.
India has the world\u2019s largest population living in slums, and
these have largely been underserved areas. The State of Food Insecurity
in the World (2012) estimates that India is home to more than 217
million undernourished people. Various studies have been conducted to
assess food insecurity at the global level; however, the literature is
limited as far as India is concerned. The present study was conducted
with the objective of documenting the prevalence of food insecurity at
the household level and the factors determining its existence in an
urban slum population of northern India. This cross-sectional study was
conducted in an urban resettlement colony of South Delhi, India. A
pre-designed, pre-tested, semi-structured questionnaire was used for
collecting socioeconomic details and information regarding dietary
practices. Food insecurity was assessed using Household Food Insecurity
Access Scale (HFIAS). Logistic regression analysis was performed to
determine the factors associated with food insecurity. A total of 250
women were interviewed through house-to-house survey. Majority of the
households were having a nuclear family (61.6%), with mean familysize
being 5.5 (SD\ub12.5) and the mean monthly household income being INR
9,784 (SD\ub1631). Nearly half (53.3%) of the mean monthly household
income was spent on food. The study found that a total of 77.2%
households were food-insecure, with 49.2% households being mildly
food-insecure, 18.8% of the households being moderately food-insecure,
and 9.2% of the households being severely food-insecure. Higher
education of the women handling food (OR 0.37, 95% CI 0.15-0.92;
p 640.03) and number of earning members in the household (OR 0.68,
95% CI 0.48-0.98; p 640.04) were associated with lesser chance/odds
of being food-insecure. The study demonstrated a high prevalence of
food insecurity in the marginalized section of the urban society. The
Government of India needs to adopt urgent measures to combat this
problem
Heterosis as Investigated in Terms of Polyploidy and Genetic Diversity Using Designed Brassica juncea Amphiploid and Its Progenitor Diploid Species
Fixed heterosis resulting from favorable interactions between the genes on their homoeologous genomes in an allopolyploid is considered analogous to classical heterosis accruing from interactions between homologous chromosomes in heterozygous plants of a diploid species. It has been hypothesized that fixed heterosis may be one of the causes of low classical heterosis in allopolyploids. We used Indian mustard (Brassica juncea, 2nβ=β36; AABB) as a model system to analyze this hypothesis due to ease of its resynthesis from its diploid progenitors, B. rapa (2nβ=β20; AA) and B. nigra (2nβ=β16; BB). Both forms of heterosis were investigated in terms of ploidy level, gene action and genetic diversity. To facilitate this, eleven B. juncea genotypes were resynthesized by hybridizing ten near inbred lines of B. rapa and nine of B. nigra. Three half diallel combinations involving resynthesized B. juncea (11Γ11) and the corresponding progenitor genotypes of B. rapa (10Γ10) and B. nigra (9Γ9) were evaluated. Genetic diversity was estimated based on DNA polymorphism generated by SSR primers. Heterosis and genetic diversity in parental diploid species appeared not to predict heterosis and genetic diversity at alloploid level. There was also no association between combining ability, genetic diversity and heterosis across ploidy. Though a large proportion (0.47) of combinations showed positive values, the average fixed heterosis was low for seed yield but high for biomass yield. The genetic diversity was a significant contributor to fixed heterosis for biomass yield, due possibly to adaptive advantage it may confer on de novo alloploids during evolution. Good general/specific combiners at diploid level did not necessarily produce good general/specific combiners at amphiploid level. It was also concluded that polyploidy impacts classical heterosis indirectly due to the negative association between fixed heterosis and classical heterosis
Ultrafast manipulation of the NiO antiferromagnetic order via sub gap optical excitation
Wide band gap insulators such as NiO offer the exciting prospect of coherently manipulating electronic correlations with strong optical fields. Contrary to metals where rapid dephasing of optical excitation via electronic processes occurs, the sub gap excitation in charge transfer insulators has been shown to couple to low energy bosonic excitations. However, it is currently unknown if the bosonic dressing field is composed of phonons or magnons. Here we use the prototypical charge transfer insulator NiO to demonstrate that 1.5 eV sub gap optical excitation leads to a renormalised NiO band gap in combination with a significant reduction of the antiferromagnetic order. We employ element specific X ray reflectivity at the FLASH free electron laser to demonstrate the reduction of the upper band edge at the O 1s 2p core valence resonance K edge whereas the antiferromagnetic order is probed via X ray magnetic linear dichroism XMLD at the Ni 2p 3d resonance L2 edge . Comparing the transient XMLD spectral line shape to ground state measurements allows us to extract a spin temperature rise of 65 5 K for time delays longer than 400 fs while at earlier times a non equilibrium spin state is formed. We identify transient mid gap states being formed during the first 200 fs accompanied by a band gap reduction lasting at least up to the maximum measured time delay of 2.4 ps. Electronic structure calculations indicate that magnon excitations significantly contribute to the reduction of the NiO band ga
Polymeric Micelles in Anticancer Therapy: Targeting, Imaging and Triggered Release
Micelles are colloidal particles with a size around 5β100Β nm which are currently under investigation as carriers for hydrophobic drugs in anticancer therapy. Currently, five micellar formulations for anticancer therapy are under clinical evaluation, of which Genexol-PM has been FDA approved for use in patients with breast cancer. Micelle-based drug delivery, however, can be improved in different ways. Targeting ligands can be attached to the micelles which specifically recognize and bind to receptors overexpressed in tumor cells, and chelation or incorporation of imaging moieties enables tracking micelles in vivo for biodistribution studies. Moreover, pH-, thermo-, ultrasound-, or light-sensitive block copolymers allow for controlled micelle dissociation and triggered drug release. The combination of these approaches will further improve specificity and efficacy of micelle-based drug delivery and brings the development of a βmagic bulletβ a major step forward
Mesostructured Block Copolymer Nanoparticles: Versatile Templates for Hybrid Inorganic/Organic Nanostructures
We present a versatile strategy to prepare a range of nanostructured poly(styrene)-block-poly(2-vinyl pyridine) copolymer particles with tunable interior morphology and controlled size by a simple solvent exchange procedure. A key feature of this strategy is the use of functional block copolymers incorporating reactive pyridyl moieties which allow the absorption of metal salts and other inorganic precursors to be directed. Upon reduction of the metal salts, well-defined hybrid metal nanoparticle arrays could be prepared, whereas the use of oxide precursors followed by calcination permits the synthesis of silica and titania particles. In both cases, ordered morphologies templated by the original block copolymer domains were obtained
Positron Emission Tomography Imaging of Endometrial Cancer Using Engineered Anti-EMP2 Antibody Fragments
E-learning During Lockdown Of Covid-19 Pandemic In India
Due to the crisis of the Covid-19 epidemic, E-learning has become an essential component of all educational institutions such as schools, colleges. The lockdown to prevent this terrible situation of Covid-19 has completely disrupted the offline learning process. E-learning offers a learning method that is primarily considered the best for students in such situations. The primary facts have been collected through a self-structured questionnaire by Google Forms to find out the attitude of undergraduate students of colleges in India towards E-learning. The objective of the presented research paper is to find out the process of E-learning among the students familiar with web based technology and this study also presents solutions to improve the self-study skills of the students. For this study, 350 respondents from all over India have been selected for demonstration using a stratified sampling method. The findings of the study suggest that the impact of E-learning on students reflects their interest in and performance in the use of E-learning resources. The findings of the study also revealed the fact that E-learning has become very popular and popular among the students especially during the period of lockdown due to the epidemic
Development of microsatellite markers and analysis of intraspecific genetic variability in chickpea (<i>Cicer arietinum</i> L.)
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