Black hole lasers in Bose-Einstein condensates

We consider elongated condensates that cross twice the speed of sound. In the absence of periodic boundary conditions, the phonon spectrum possesses a discrete and finite set of complex frequency modes that induce a laser effect. This effect constitutes a dynamical instability and is due to the fact that the supersonic region acts as a resonant cavity. We numerically compute the complex frequencies and density-density correlation function. We obtain patterns with very specific signatures. In terms of the gravitational analogy, the flows we consider correspond to a pair of black hole and white hole horizons, and the laser effect can be conceived as a self-amplified Hawking radiation. This is verified by comparing the outgoing flux at early time with the standard black hole radiation.Comment: iopams, 37 pages, 14 figures, 1 table; for associated gif animations, see http://people.sissa.it/~finazzi/bec_bhlasers/movies/ or http://iopscience.iop.org/1367-2630/12/9/095015/media. Published on New. J. Phys. (http://iopscience.iop.org/1367-2630/12/9/095015/). V2: few new comments, modified figure

Impact of Crude Oil on Soil Nitrogen Dynamics and Up-take by Legumes Grown in Wetland Ultisol of the Niger Delta

Abstract The effects of crude oil on soil nitrogen dynamics and cycling in plant-soil ecosystems and its effect on the growth of legumes (Calopogonium mucunoides, Centrosema pubescens and Pueraria phaseolodes) grown in wetland ultisols were investigated. The test plants species were grown on wetland soil simulated with 0.35, 10.8, 20.5, and 50 g•kg −1 levels of crude oil contamination. The results showed time and species dependent variation in mineral N content of the treated soils. The variation is indicative of significant interaction between the hydrocarbon content and plant species. Variations in microbial N and microbial C were similar and correlation between the microbial N and the total C (Organic matter (C) + hydrocarbon content (C)) in soil was highly significant (r = 0.96, n = 12, P ≤ 0.01). The presence of hydrocarbon contaminant widens the C:N ratio in soil and leads to more available N being immobilized by soil microorganisms, which reduces available N for plant uptake. This result implies that crude oil contamination significantly reduces N uptake by plants but increases N accumulation in soil microbial biomass. The findings show that N dynamics, transformation and cycling in soil are influenced by hydrocarbons and that the interactions between hydrocarbon content and plant species in contaminated soil are remarkable. The use of plant Centrosema pubescens with poultry manure or NPK fertilizer for bioremediation is more effective than that of Calopogonium mucunoides and Pueraria phaseoloides. However, the selective attributes of the various treatment approaches adopted here may be exploited for enhanced remediation of contaminated wetlands in the Niger Delta region of Nigeria

Dynamics of fluctuations in an optical analog of the Laval nozzle

Using the analogy between the description of coherent light propagation in a medium with Kerr nonlinearity by means of nonlinear Schr\"odinger equation and that of a dissipationless liquid we propose an optical analogue of the Laval nozzle. The optical Laval nozzle will allow one to form a transonic flow in which one can observe and study a very unusual dynamics of classical and quantum fluctuations including analogue of the Hawking radiation of real black holes. Theoretical analysis of this dynamics is supported by numerical calculations and estimates for a possible experimental setup are presented.Comment: 7 pages, 4 figure

Crude Oil-Degradation and Plasmid Profile of Nitrifying Bacteria Isolated from Oil-Impacted Mangrove Sediment in the Niger Delta of Nigeria

The crude oil degradability and plasmid profile of autotrophic nitrifying bacteria, Nitrosomonas and Nitrobacter species, isolated from mangrove sediment in the Niger Delta of Nigeria were studied. The effects of temperature, pH and optical density on the utilization of different carbon sources by the bacteria were also investigated. Results showed that nitrifying bacteria could utilize kerosene, diesel oil, jet fuel and engine oil as carbon sources. None utilized hexane and xylene but moderate growth was observed in benzene, phenol and toluene. However, their ability to utilized crude oil varied both in rates of utilization and in growth profiles. Mixed culture of the isolates degrades 52 % of crude oil introduced into the medium followed by Nitrosomonas sp. with 40 % degradation. The least was Nitrobacter sp. with 20 % degradation. The ability of the autotrophs to degrade crude oil was found to be plasmid-mediated through curing experiment and electrophoresis. The size of the plasmid involved was estimated to be 23 kb. The high crude oil utilization of the mixed culture implies that nitrifying bacteria isolated from contaminated ecosystem are excellent crude oil degraders and can be harnessed for bioremediation purposes

Development and validation of a microbial counting method for mebendazole oral suspension

Mebendazole is an important medicine used to treat helminth infections. These infections affect more than two billion people worldwide. The LAFEPE® (Recife-PE, Brazil) produces the drug mebendazole oral suspension that contains the preservatives methylparaben and propylparaben in its formulation. Drugs that have antimicrobial properties due to preservatives must undergo neutralization of these compounds to allow microbial count testing according to recommendations by the official compendia. In order to obtain a validated method for microbial counting and to ensure its safety and reliability within the pharmaceutical industry, validation of preservative neutralization and of the method for microbial counting was performed according to the USP 30 and PDA Technical Report No. 33. The method used ATCC Gram positive and Gram negative microorganisms, yeasts, most and culture media Tryptic Soy Agar and Sabouraud dextrose agar. The neutralizers were polysorbate 80 and lecithin. Recovery levels of over 70% of the microorganisms used in the test indicated the neutralization of antimicrobial activity and proved the absence of toxicity of neutralizers. The microbial counting method validated proved accurate, precise, robust and linear and can be safely used in routine operations.O mebendazol é um importante medicamento utilizado no tratamento de infecções por helmintos. Essas infecções afetam mais de dois bilhões de pessoas em todo o mundo. O LAFEPE (Recife-PE, Brasil) produz o medicamento mebendazol suspensão oral, que possui em sua formulação os conservantes metilparabeno e propilparabeno. Em medicamentos que possuem propriedades antimicrobianas em decorrência dos conservantes faz-se necessária a neutralização da ação desses compostos para a realização do teste de contagem microbiana segundo preconizado pelos compêndios oficiais. A fim de obter um método de contagem microbiana validado e que garanta sua segurança e reprodutibilidade dentro da indústria farmacêutica foi realizada a validação da neutralização dos antimicrobianos e validação do método de contagem microbiana de acordo com a USP 30 e PDA-Technical Report N° 33. O método desenvolvido utilizou microrganismos ATCC Gram positivos, Gram negativos, leveduras e fungos e meios de cultura Tryptic Soy Agar e Sabouraud-dextrose Agar. Os neutralizantes foram polissorbato 80 e lecitina de soja . Níveis de recuperação superiores a 70% dos microrganismos utilizados no ensaio indicaram neutralização da atividade antimicrobiana e comprovou a ausência de toxicidade dos neutralizantes. O método de contagem microbiana validado revelou-se exato, preciso, robusto e linear podendo ser utilizado com segurança na rotina operacional

Marine Tar Residues: a Review

Abstract Marine tar residues originate from natural and anthropogenic oil releases into the ocean environment and are formed after liquid petroleum is transformed by weathering, sedimentation, and other processes. Tar balls, tar mats, and tar patties are common examples of marine tar residues and can range in size from millimeters in diameter (tar balls) to several meters in length and width (tar mats). These residues can remain in the ocean envi-ronment indefinitely, decomposing or becoming buried in the sea floor. However, in many cases, they are transported ashore via currents and waves where they pose a concern to coastal recreation activities, the seafood industry and may have negative effects on wildlife. This review summarizes the current state of knowledge on marine tar residue formation, transport, degradation, and distribution. Methods of detection and removal of marine tar residues and their possible ecological effects are discussed, in addition to topics of marine tar research that warrant further investigation. Emphasis is placed on ben-thic tar residues, with a focus on the remnants of the Deepwater Horizon oil spill in particular, which are still affecting the northern Gulf of Mexico shores years after the leaking submarine well was capped

Fate of Nitrogen-Fixing Bacteria in Crude Oil Contaminated Wetland Ultisol

The effect of crude oil on the growth of legumes (Calopogonium muconoides and Centrosema pubescens) and fate of nitrogen-fixing bacteria in wetland ultisol was investigated using standard cultural techniques. The results revealed observable effects of oil on soil physico-chemistry, plant growth and nodulation as well as on densities of heterotrophic, hydrocarbonoclastic and nitrogen fixing bacteria. The effects however varied with different levels (0.5%, 1%, 5%, 10%, 15% and 20%) of pollution. Ammonium and nitrate levels were high in the unpolluted soil but decreased with increase in pollution levels. Nitrite was not detected in contaminated soil probably due to the reduction in numbers of nitrogen fixers, from 5.26 ± 0.23 × l06cfu/g in unpolluted soil to 9.0 ± 0.12 × 105 and 2.2 ± 0.08 × l05 cfu/g in soils with 5% and 20% levels of pollution respectively. The contaminated soil also exhibited gross reduction in the nodulation of legumes. A range of 13–57 nodules was observed in legumes from polluted soil against 476 nodules recorded for plants cultured on unpolluted soil. The heterogeneity of the microbial loads between oil-polluted and unpolluted soil were statistically significant (p < 0.05, ANOVA). Positive significant relationships were observed between the levels of hydrocarbons and the densities of heterotrophic bacteria (r = 0.91) and that of hydrocarbon utilizing bacteria (r = 0.86). On the other hand, relationships between the densities of nitrogen fixing bacteria and total hydrocarbons content was negative (r = −0.30) while positive relationships were recorded between the densities of different microbial groups and treatment periods except at 15% and 20% pollution levels. The LSD tests revealed highly significant differences (p < 0.001) in the physiological groups of soil microorganisms at all levels of pollution. The results imply that crude oil seriously affects rhizosphere microbial growth in legumes. Among the bacterial species isolated, Clostridium pasteurianum, Bacillus polymyxa and Pseudomonas aeruginosa exhibited greater ability to degrade hydrocarbons than Azotobacter sp, Klebsiella pneumoniae and Derxia gummusa while Nitrosomonas and Nitrobacter had the least degradability. A continuous monitoring of the environment is advocated to prevent extinction of nitrogen-fixing bacteria and total loss of soil fertility attributable to petroleum hydrocarbon contamination in the Niger Delta ultisol

Influence of electrical conductivity on microorganisms and rate of crude oil mineralization in Niger Delta ultisol

The effect of salinity on the population density of hydrocarbonoclastic microorganisms and oil degradation in a tropical ultisol was determined. Soils were simulated with 50gkg-1 of Qua Iboe Light (QIL) crude oil. Salt treatments included NaCI amendments to adjust the soil solution electrical conductivities (EC) to 40, 120 and 200 dSm-1. Treated soils were incubated at 28OC. Oil degradation was estimated from the gravimetric determinations of remaining oil. The results showed that amending the ultisol with crude oil stimulated the growth of oil degrading microorganisms, while salt concentration inducing an EC of 200 dSm-1 in oil amended ultisol resulted in a decrease in the amount oil mineralized. A significant positive correlation was found between the number of hydrocarbonoclastic microorganisms and levels of oil mineralization at EC 40 dSm-1 (r = 0.980, P = 0.05) and EC 120 dSm-1 (r = 0.976. P = 0.05) except at EC 200 dSm-1 (r = 0.855, P = 0.05). This is an indication that desalting of soils contaminated with oil and salts is required for a speedy bioremediation of an ultisol. Key words: Electrical conductivity, crude oil, hydrocarbonoclastic microorganismineralization. (Global Journal of Pure and Applied Sciences: 2003 9(4): 475-480

Prevalence of enteropathogens and their association with diarrhea among children of food vendors in Uyo, Nigeria

A survey of enteropathogens (bacteria-parasite co-infections) was carried out among 370 children of food vendors in Uyo, Nigeria. Faecal samples (311 formed and 59 diarrhoeic stools) were screened for intestinal helminths using standard parasitological procedures. The prevalence of the parasites encountered was: Hookworm (49.5%); Ascaris lumbricoides (42.8%) Trichuris trichiura (24.9%); Strongyloides stercoralis (2.7%); Entamoeba histolytica (10.0%) and Giardia lamblia (7.8%). Bacteriological analyses of the diarrhoeic stolls revealed the following bacterial isolates: Campylobacter species, Shigella species, Escherichia coli, Salmonella typhi, Yersinia enterocolitica, Clostridium species, Aeromonas hydrophila and Vibrio species. A strong association between the bacterial isolates and protozoan parasites (Entamoeba histolytica and Giardian lamblia) in diarrhoeic stools was evident. There was no significant (X2 = 0.44; P > 0.05) difference between infection and sex. All infections declined gradually with age but it was not statistically significant (X2 = 6.17; P > 0.001). A significant relationship existed between infection and type of school attended by the children (X2 = 19.65; P < 0.05), source of water supply (X2 = 13.59; P < 0.05) and type of toilet facility used (X2 = 68.83; P < 0.01). Since children are veritable sources of food contamination, the enforcement of hygienic practices therefore becomes imperative. Keywords: parasites, bacteria, children, food vendors, diarrhea, Nigeria Mary Slessor Journal of Medicine Vol. 5(1), 2005: 11-2