Evaluation of portable water in five provinces of Zambia using a water pollution index

Five provinces with different environmental characteristics were evaluated for water pollution with the aim of identifying the major sources and area(s) most affected. The results indicate that the water in Lusaka Province is significantly high in nitrate and sodium concentration compared to other provinces considered in this study. The results further reveal that ground water is most affected by nitrate and sodium. On the contrary, dissolved organic carbon (DOC) was found to be significantly higher in surface water but no particular province registered a higher amount compared to others. The results further reveal that the pollution is primarily a function of human activities, social amenities and industrial activities in the study areas.Key words: Nitrate, sulphate, groundwater, Lusaka, ion exchange/cation-exchange chromatography

Exactly solvable strings in Minkowski spacetime

We study the integrability of the equations of motion for the Nambu-Goto strings with a cohomogeneity-one symmetry in Minkowski spacetime. A cohomogeneity-one string has a world surface which is tangent to a Killing vector field. By virtue of the Killing vector, the equations of motion can be reduced to the geodesic equation in the orbit space. Cohomogeneity-one strings are classified into seven classes (Types I to VII). We investigate the integrability of the geodesic equations for all the classes and find that the geodesic equations are integrable. For Types I to VI, the integrability comes from the existence of Killing vectors on the orbit space which are the projections of Killing vectors on Minkowski spacetime. For Type VII, the integrability is related to a projected Killing vector and a nontrivial Killing tensor on the orbit space. We also find that the geodesic equations of all types are exactly solvable, and show the solutions.Comment: 11 pages, a reference added, some points clarifie

All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators

We review our recent work on tunable, ultrahigh quality factor whispering-gallery-mode bottle microresonators and highlight their applications in nonlinear optics and in quantum optics experiments. Our resonators combine ultra-high quality factors of up to Q = 3.6 \times 10^8, a small mode volume, and near-lossless fiber coupling, with a simple and customizable mode structure enabling full tunability. We study, theoretically and experimentally, nonlinear all-optical switching via the Kerr effect when the resonator is operated in an add-drop configuration. This allows us to optically route a single-wavelength cw optical signal between two fiber ports with high efficiency. Finally, we report on progress towards strong coupling of single rubidium atoms to an ultra-high Q mode of an actively stabilized bottle microresonator.Comment: 20 pages, 24 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: minor corrections to some figures and captions, clarification of some points in the text, added references, added new paragraph with results on atom-resonator interactio

Accelerated expansion from structure formation

We discuss the physics of backreaction-driven accelerated expansion. Using the exact equations for the behaviour of averages in dust universes, we explain how large-scale smoothness does not imply that the effect of inhomogeneity and anisotropy on the expansion rate is small. We demonstrate with an analytical toy model how gravitational collapse can lead to acceleration. We find that the conjecture of the accelerated expansion being due to structure formation is in agreement with the general observational picture of structures in the universe, and more quantitative work is needed to make a detailed comparison.Comment: 44 pages, 1 figure. Expanded treatment of topics from the Gravity Research Foundation contest essay astro-ph/0605632. v2: Added references, clarified wordings. v3: Published version. Minor changes and corrections, added a referenc

Učinkovitost u zadacima fine motorike i prostornih odnosa tijekom menstrualnog ciklusa

Various studies have shown fl uctuations in task performance during the menstrual cycle. The aim of this study was to see the effects of the menstrual cycle on performing fi ne motor and spatial tasks of different level of complexity in twenty students aged 18 to 21 years, with regular menstrual cycle (28 to 30 days). The students performed O’Connor Finger Dexterity Test and mental rotation test during the menstrual, late follicular, and midluteal phase. Before the tests were performed, we administered Spielberger’s State-Trait Anxiety Inventory for each phase. After the tasks were completed, the subjects ranked their diffi culty on Borg’s scale. The results showed the best performance in both tests in the midluteal phase (with sex hormones at their peak). The anxiety level and task diffi culty ranking were the highest in the menstrual phase, when the hormone levels were the lowest.Različita su istraživanja pokazala promjene učinkovitosti tijekom menstrualnog ciklusa. U zadacima u kojima su uspješnije žene, najveća učinkovitost događa se tijekom kasne folikularne ili srednje lutealne faze. U zadacima u kojima su pak uspješniji muškarci najveća je učinkovitost nađena u menstrualnoj fazi. Na osnovi uporabe zadataka fi ne motorike i prostornih zadataka različitih razina kompleksnosti, cilj ovog istraživanja bio je ispitati utjecaj menstrualnog ciklusa na kognitivne funkcije. U istraživanju je sudjelovalo dvadeset ispitanica, dobi od 18 do 21 godinu, s redovitim menstrualnim ciklusima (28 do 30 dana). Ispitanice su izvodile O’Connorov deksterimetar i zadatke mentalne rotacije tijekom menstrualne, kasne folikularne i srednje lutealne faze. Prije izvođenja zadataka, u svakoj fazi ciklusa primijenjen je Spielbergerov upitnik stanja anksioznosti. Nakon izvođenja zadataka, ispitanice su procjenjivale njihovu težinu na Borgovoj skali. Rezultati su pokazali najbolju učinkovitost u oba zadatka u fazi visokih razina spolnih hormona (srednja lutealna faza). Stanje anksioznosti i procijenjene težine zadataka bili su najviši u menstrualnoj fazi, kada su razine spolnih hormona najniže

The effect of inhomogeneous expansion on the supernova observations

We consider an inhomogeneous but spherically symmetric Lemaitre-Tolman-Bondi model to demonstrate that spatial variations of the expansion rate can have a significant effect on the cosmological supernova observations. A model with no dark energy but a local Hubble parameter about 15% larger than its global value fits the supernova data better than the homogeneous model with the cosmological constant. The goodness of the fit is not sensitive to inhomogeneities in the present-day matter density, and our best fit model has Omega_M ~ 0.3, in agreement with galaxy surveys. We also compute the averaged expansion rate, defined by the Buchert equations, of the best fit model and show explicitly that there is no average acceleration.Comment: minor corrections to match the version published in JCA

Identification and Functional Analysis of Epigenetically Silenced MicroRNAs in Colorectal Cancer Cells

Abnormal microRNA (miRNA) expression has been linked to the development and progression of several human cancers, and such dysregulation can result from aberrant DNA methylation. While a small number of miRNAs is known to be regulated by DNA methylation, we postulated that such epigenetic regulation is more prevalent. By combining MBD-isolated Genome Sequencing (MiGS) to evaluate genome-wide DNA methylation patterns and microarray analysis to determine miRNA expression levels, we systematically searched for candidate miRNAs regulated by DNA methylation in colorectal cancer cell lines. We found 64 miRNAs to be robustly methylated in HCT116 cells; eighteen of them were located in imprinting regions or already reported to be regulated by DNA methylation. For the remaining 46 miRNAs, expression levels of 18 were consistent with their DNA methylation status. Finally, 8 miRNAs were up-regulated by 5-aza-2′-deoxycytidine treatment and identified to be novel miRNAs regulated by DNA methylation. Moreover, we demonstrated the functional relevance of these epigenetically silenced miRNAs by ectopically expressing select candidates, which resulted in inhibition of growth and migration of cancer cells. In addition to reporting these findings, our study also provides a reliable, systematic strategy to identify DNA methylation-regulated miRNAs by combining DNA methylation profiles and expression data