Numerical Simulation of the Performance Characteristics of the Hybrid Closed Circuit Cooling Tower

The performance characteristics of the Hybrid Closed Circuit Cooling Tower (HCCCT) have been investigated applying computational fluid dynamics (CFD). Widely reported CFD techniques are applied to simulate the air-water two phase flow inside the HCCCT. The pressure drop and the cooling capacity were investigated from several perspectives. Three different transverse pitches were tested and found that a pitch of 45 mm had lower pressure drop. The CFD simulation indicated that when air is supplied from the side wall of the HCCCT, the pressure drop can be over predicted and the cooling capacity can be under predicted mainly due to the non-uniform air flow distribution across the coil bank. The cooling capacity in wet mode have been calculated with respect to wet-bulb temperature (WBT) and cooling water to air mass flow rates for different spray water volume flow rates and the results were compared to the experimental measurement and found to conform well for the air supply from the bottom end. The differences of the cooling capacity and pressure drop in between the CFD simulation and experimental measurement in hybrid mode were less than 5 % and 7 % respectively for the uniform air flow distribution

Data describing the eco-physiological responses of Elaeagnus angustifolia grown under contrasting regime of water and fertilizer in coal-mined spoils

To improve our understanding of how coal mining areas can be re-vegetated and ecosystem function restored, we examined the potential effects of five water (W) regimes (40, 50, 60, 70 and 80% of field capacity), five nitrogen (N) (0, 24, 60, 96 and 120 mg kg‒1 soil) and five phosphorus (P) fertilizer doses (0, 36, 90, 144 and 180 mg kg‒1 soil), which control the growth and development of Elaeagnus angustifolia under adverse environmental conditions. To optimize the W-N-P application rate, three factors and five levels of central composite design along with an optimization technique named response surface methodology were utilized. Here we provide data on root-shoot biomass ratio, leaf dry matter content, stomatal conductance, chlorophyll (Chl) a, Chl b, membrane stability index and soluble protein content of E. angustifolia. The data described in this article are available in Mendeley Data, DOI: 10.17632/2vfbrdxyf2.2 [1]. These data could be used to evaluate the improvement in growth performance of E. angustifolia subjected to various regimes of W, N and P. This dataset showed that E. angustifolia grew optimally in coal-mine spoils when irrigated at 66% of field capacity and supplemented with 74.0 mg N and 36.0 mg P kg‒1 soil. This could considerably help the success of revegetation in coal-mined degraded arid areas where W is scarce. This article contains data complementary to the main research entitled "Fine-tuning of soil water and nutrient fertilizer levels for the ecological restoration of coal-mined spoils using Elaeagnus angustifolia" in the Journal of Environmental Management (Roy et al., 2020)

Temperature dependence of the resistivity in the double-exchange model

The resistivity around the ferromagnetic transition temperature in the double exchange model is studied by the Schwinger boson approach. The spatial spin correlation responsible for scattering of conduction electrons are taken into account by adopting the memory function formalism. Although the correlation shows a peak lower than the transition temperature, the resistivity in the ferromagnetic state monotonically increases with increasing temperature due to a variation of the electronic state of the conduction electron. In the paramagnetic state, the resistivity is dominated by the short range correlation of scattering and is almost independent of the temperature. It is attributed to a cancellation between the nearest-neighbor spin correlation, the fermion bandwidth, and the fermion kinetic energy. This result implies the importance of the temperature dependence of the electronic states of the conduction electron as well as the localized spin states in both ferromagnetic and paramagnetic phases.Comment: RevTex, 4 pages, 4 PostScript figures, To appear in Phys. Rev.

Considerations on the quantum double-exchange Hamiltonian

Schwinger bosons allow for an advantageous representation of quantum double-exchange. We review this subject, comment on previous results, and address the transition to the semiclassical limit. We derive an effective fermionic Hamiltonian for the spin-dependent hopping of holes interacting with a background of local spins, which is used in a related publication within a two-phase description of colossal magnetoresistant manganites.Comment: 7 pages, 3 figure

What Influences Adolescent Girls' Decision-Making Regarding Contraceptive Methods Use and Childbearing? A Qualitative Exploratory Study in Rangpur District, Bangladesh

BACKGROUND: Bangladesh has the highest rate of adolescent pregnancy in South Asia. Child marriage is one of the leading causes of pregnancies among adolescent girls. Although the country's contraceptive prevalence rate is quite satisfactory, only 52% of married adolescent girls use contraceptive methods. This qualitative study is aimed at exploring the factors that influence adolescent girls' decision-making process in relation to contraceptive methods use and childbearing. METHODS AND RESULTS: We collected qualitative data from study participants living in Rangpur district, Bangladesh. We conducted 35 in-depth interviews with married adolescent girls, 4 key informant interviews, and one focus group discussion with community health workers. Adolescent girls showed very low decision-making autonomy towards contraceptive methods use and childbearing. Decisions were mainly made by either their husbands or mothers-in-law. When husbands were unemployed and financially dependent on their parents, then the mothers-in-law played most important role for contraceptive use and childbearing decisions. Lack of reproductive health knowledge, lack of negotiation and communication ability with husbands and family members, and mistrust towards contraceptive methods also appeared as influential factors against using contraception resulting in early childbearing among married adolescent girls. CONCLUSIONS: Husbands and mothers-in-law of newly married adolescent girls need to be actively involved in health interventions so that they make more informed decisions regarding contraceptive use to delay pregnancies until 20 years of age. Misunderstanding and distrust regarding contraceptives can be diminished by engaging the wider societal actors in health intervention including neighbours, and other family members

Ground State of the Singly Ionized Oxygen Vacancy in Rutile TiO\u3csub\u3e2\u3c/sub\u3e

Results from electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) experiments are used to establish the model for the ground state of the singly ionized oxygen vacancy in the interior of bulk rutile TiO2 crystals. Hyperfine from 47Ti and 49Ti nuclei show that the unpaired electron in this S = 1/2 defect is localized on one titanium ion adjacent to the oxygen vacancy (i.e., the spin is not shared by two titanium ions). These defects are formed at low temperature (∼35 K) in as-grown oxidized crystals when sub-band-gap 442 nm laser light converts doubly ionized nonparamagnetic oxygen vacancies to the singly ionized paramagnetic charge state. The g matrix is obtained from EPR spectra and the 47Ti and 49Ti hyperfine and nuclear electric quadrupole matrices (A and Q) are obtained from ENDOR spectra. Principal values of the 47Ti and 49Ti hyperfine matrices are 64.54, 11.57, and 33.34 MHz. All the matrices have a principal axis along the [001] direction. In the basal plane, principal axes of the hyperfine and quadrupole matrices also coincide. The principal axes of the g matrix in the basal plane, however, deviate significantly from those of the A and Q matrices, thus indicating mixing of d orbitals due to the low symmetry at the Ti3+ ion site and participation of excited-state orbitals

Three-dimensional organotypic co-culture model of intestinal epithelial cells and macrophages to study Salmonella enterica colonization patterns

Three-dimensional models of human intestinal epithelium mimic the differentiated form and function of parental tissues often not exhibited by two-dimensional monolayers and respond to Salmonella in key ways that reflect in vivo infections. To further enhance the physiological relevance of three-dimensional models to more closely approximate in vivo intestinal microenvironments encountered by Salmonella, we developed and validated a novel three-dimensional co-culture infection model of colonic epithelial cells and macrophages using the NASA Rotating Wall Vessel bioreactor. First, U937 cells were activated upon collagen-coated scaffolds. HT-29 epithelial cells were then added and the three-dimensional model was cultured in the bioreactor until optimal differentiation was reached, as assessed by immunohistochemical profiling and bead uptake assays. The new co-culture model exhibited in vivo-like structural and phenotypic characteristics, including three-dimensional architecture, apical-basolateral polarity, well-formed tight/adherens junctions, mucin, multiple epithelial cell types, and functional macrophages. Phagocytic activity of macrophages was confirmed by uptake of inert, bacteria-sized beads. Contribution of macrophages to infection was assessed by colonization studies of Salmonella pathovars with different host adaptations and disease phenotypes (Typhimurium ST19 strain SL1344 and ST313 strain D23580; Typhi Ty2). In addition, Salmonella were cultured aerobically or microaerobically, recapitulating environments encountered prior to and during intestinal infection, respectively. All Salmonella strains exhibited decreased colonization in co-culture (HT-29-U937) relative to epithelial (HT-29) models, indicating antimicrobial function of macrophages. Interestingly, D23580 exhibited enhanced replication/survival in both models following invasion. Pathovar-specific differences in colonization and intracellular co-localization patterns were observed. These findings emphasize the power of incorporating a series of related three-dimensional models within a study to identify microenvironmental factors important for regulating infection

Low Temperature Magnetic Properties of the Double Exchange Model

We study the {\it ferromagnetic} (FM) Kondo lattice model in the strong coupling limit (double exchange (DE) model). The DE mechanism proposed by Zener to explain ferromagnetism has unexpected properties when there is more than one itinerant electron. We find that, in general, the many-body ground state of the DE model is {\it not} globally FM ordered (except for special filled-shell cases). Also, the low energy excitations of this model are distinct from spin wave excitations in usual Heisenberg ferromagnets, which will result in unusual dynamic magnetic properties.Comment: 5 pages, RevTeX, 5 Postscript figures include

A Theory of Magnets with Competing Double Exchange and Superexchange Interactions

We study the competition between ferromagnetic double exchange (DE) and nearest-neighbour antiferromagnetic exchange in CMR materials. Towards this end, a single site mean field theory is proposed which emphasizes the hopping-mediated nature of the DE contribution. We find that the competition between these two exchange interactions leads to ferro- or antiferromagnetic order with incomplete saturation of the (sub)lattice magnetization. This conclusion is in contrast to previous results in the literature which find a canted spin arrangement under similar circumstances. We attribute this difference to the highly anisotropic exchange interactions used elsewhere. The associated experimental implications are discussed.Comment: 4 pages, Latex-Revtex, 3 PostScript figures. Please see report cond-mat/980523

Stability of homogeneous magnetic phases in a generalized t-J model

We study the stability of homogeneous magnetic phases in a generalized t-J model including a same-sublattice hopping t' and nearest-neighbor repulsion V by means of the slave fermion-Schwinger boson representation of spin operators. At mean-field order we find, in agreement with other authors, that the inclusion of further-neighbor hopping and Coulomb repulsion makes the compressibility positive, thereby stabilizing at this level the spiral and Neel orders against phase separation. However, the consideration of Gaussian fluctuation of order parameters around these mean-field solutions produces unstable modes in the dynamical matrix for all relevant parameter values, leaving only reduced stability regions for the Neel phase. We have computed the one-loop corrections to the energy in these regions, and have also briefly considered the effects of the correlated hopping term that is obtained in the reduction from the Hubbard to the t-J model.Comment: 5 pages, 5 figures, Revte