Relaxation Of Brownian Particles In A Gravitational Field

We describe an upper level undergraduate experiment on the time-dependent behavior of a suspension of Brownian particles under gravitational attraction. We employed the Fokker-Planck equation in the strong friction limit and measured the time-evolution of the probability distribution for 1.0 mu m diameter latex Brownian particles in water at room temperature and pressure. The experiment provides evidence of the atomic nature of water.Physic

A slow mode wave as a possible source of Pi 2 and associated particle precipitation: a case study

International audienceAn intensification of auroral luminosity referred to as an auroral break-up often accompanies the onset of geomagnetic pulsation (Pi 2) at the dip-equator. One such auroral break-up occurred at 2239 UT on 16 June, 1986, being accompanied by weak substorm activity (AE~50 nT) which was recorded in all-sky image of Syowa Station, Antarctica (66.2°S, 71.8°E in geomagnetic coordinates). The associated Pi 2 magnetic pulsation was detected by a fluxgate magnetometer in the afternoon sector at the dip-equator (Huancayo, Peru; 1.44°N, 355.9° in geomagnetic coordinates; 12.1°S, 75.2°W in geographic coordinates; L=1.00). In spite of the large separation of the two stations in longitude and latitude, the auroral break-up and subsequent luminosity modulation were seen to be correlated with the wave form of the ground Pi 2 pulsation. This occurred in such a way that the luminosity maximum was seen to occur at the phase of maximum amplitudes of Pi 2 wave form. We argue that the observed correlation could be interpreted as indicating a Pi 2-modulation of a field-aligned acceleration of the low energy electrons that may occur near the equator of the midnight magnetosphere

PELATIHAN PEMANFAATAN TEKNOLOGI DALAM PEMBELAJARAN MATEMATIKA BAGI GURU MATEMATIKA SE-KECAMATAN SULAMU KABUPATEN KUPANG

Tujuan dari kegiatan pengabdian kepada masyarakat ini adalah memberikan pemahaman kepada guru matematika bagaimana pemanfaatan teknologi yang benar dalam pembelajaran matematika serta keterampilan menggunakan software pembelajaran dinamis seperti GeoGebra dalam pembelajaran matematika. Jumlah guru yang terlibat dalam kegiatan ini sebanyak 30 guru. Metode kegiatan ini adalah ceramah, diskusi, tanyajawab, dan latihan mandiri. Kegiatan pengabdian kepada masyarakat ini akan dilaksanakan dalam beberapa tahapan, yaitu 1) penyampaian materi oleh narasumber mengenai pembelajaran abad 21, pemanfaatan teknologi dalam pembelajaran matematika, serta penggunaan GeoGebra sebagai media pembelajaran visual; 2) latihan mandiri penggunaan GeoGebra, 3) pengisian angket pemahaman tentang pemanfaatan teknologi dalam pembelajaran, serta 4) rencana tindak lanjut. Selama kegiatan, para guru antusias mengikuti materi, berdiskusi, dan mencoba menggunakan GeoGebra. Pemanfaatan teknologi khususnya penggunaan GeoGebra dalam pembelajaran matematika merupakan sesuatu yang baru bagi guru sehingga sangat membantu mereka mengembangkan pembelajaran yang inovatif sesuai tuntutan pembelajaran saat ini. Berdasarkan angket pemahaman pemanfaatan teknologi dalam pembelajaran, hasil pelatihan dipahami dengan baik oleh para guru dalam kategori sangat baik

N=1/2 Supersymmetric gauge theory in noncommutative space

A formulation of (non-anticommutative) N=1/2 supersymmetric U(N) gauge theory in noncommutative space is studied. We show that at one loop UV/IR mixing occurs. A generalization of Seiberg-Witten map to noncommutative and non-anticommutative superspace is employed to obtain an action in terms of commuting fields at first order in the noncommutativity parameter tetha. This leads to abelian and non-abelian gauge theories whose supersymmetry transformations are local and non-local, respectively.Comment: One reference added, published versio

HIV prevalence and behavioral studies in female sex workers in Togo: a decline in the prevalence between 2005 and 2011

Introduction: We determined the sero-prevalence of HIV among female sex workers (FSWs) in Togo identified their sexual risk behaviors.Methods: We conducted a cross-sectional study from 17 to 27 December, 2011 on 1106 FSWs in Togo. Venous sample were collected to estimate HIV prevalence as per national algorithms. Behavior data were collected by interviewer-administered questionnaires. Results: Of the 1106 FSWs (mean age = 27.6 years) surveyed, 17% and 63% had their first sexual intercourse before the age of 15 and 18 years respectively. Overall, 43.4% of the FSWs had more than seven clients per week. Most FSWs (95%) said they had sex using a condom in their lifetime while 8.8% had used a condom during their last sexual intercourse. About 79% of FSWs used a condom during their sexual encounters the previous week and 11.6% had used a condom during each of their sexual encounters the previous day. Most FSWs (62.2%) reported to have been tested for HIV. Of these, 145 (13.1%) were HIV positive. HIV sero-prevalence decreased from 19.4% in the south to 7.5% in the north of the country. Behaviors associated with FSW being HIV positive included: FSW having more than 7 clients per week (p<0.001), not using condoms at every intercourse act (p=0.003) or during the last sexual encounter (p=0.006) and trading sex in brothels (p<0.001). Conclusion: We estimate HIV sero-prevalence among FSWs in 2011 to be 13.1% in Togo, significantly lower than a prevalence of 29.5% estimated previously in 2005. Inconsistent use of condoms was identified as associated with high risk factor for acquiring HIV.Key words: Sex workers, HIV, sexual behavior, Tog

Etude des propriétés magnéto-optiques des couches minces à base de ferrite de cobalt obtenues par voie sol-gel

Ce travail est consacré à l'étude des propriétés magnéto-optiques (rotation Faraday) de couches minces à base de ferrite de cobalt obtenues par voie sol-gel. La contribution de la méthode sol-gel utilisée est très importante et cela permet d’obtenir des couches minces ayant une bonne qualité optique. Cette démarche nécessite juste l’utilisation de liquides magnétiques ou ferro fluides, de précurseurs de silice (pas cher) et d’un substrat de verre. Le but est d’obtenir des couches minces et étudier leurs propriétés magnéto-optiques. Les courbes obtenues à la longueur d’onde de 820 nm présentent des cycles d’hystérésis avec des rotations rémanentes de 40, 60 et 81°/cm. Ces résultats présentent une excellente rotation Faraday de 212, 318 et 340°/cm à la longueur d’onde de 820 nm. Ceci montre la forte potentialité de la matrice sol-gel dopée.Mots-clés: nanoparticules magnétiques, ferrite de cobalt, sol-gel, couches minces, rotation Faraday. Study of themagneto-optical properties of thin films cobalt ferrite obtainedby the sol-gel This work is devoted to the study of magneto-optical (Faraday rotation) of thin cobalt ferrite layers obtained by sol-gel. The contribution of the sol-gel method is very important and it allows obtaining thin film shaving a good optical quality. This requires only the use of magnetic fluids or ferro fluids, silica precursors (cheap) and a glass substrate. The goal is to obtain thin layers and study their magneto-optical properties. The curves obtained for the wave length of 820 nm have hysteresis loops with retentive rotations of 40, 60 and 81°/ cm. These results show excellentFaradayrotation 212, 318 and 340°/cm ata wave length of 820 nm. This shows the high potential of the doped sol-gel matrix.Keywords: agnetic nanoparticles, cobalt ferrite, sol-gel, thin films, Faraday rotation

Subversion of actin dynamics by EspM effectors of attaching and effacing bacterial pathogens

Rho GTPases are common targets of bacterial toxins and type III secretion system effectors. IpgB1 and IpgB2 of Shigella and Map of enteropathogenic (EPEC) and enterohemorrhagic (EHEC) Escherichia coli were recently grouped together on the basis that they share a conserved WxxxE motif. In this study, we characterized six WxxxE effectors from attaching and effacing pathogens: TrcA and EspM1 of EPEC strain B171, EspM1 and EspM2 of EHEC strain Sakai and EspM2 and EspM3 of Citrobacter rodentium. We show that EspM2 triggers formation of global parallel stress fibres, TrcA and EspM1 induce formation of localized parallel stress fibres and EspM3 triggers formation of localized radial stress fibres. Using EspM2 and EspM3 as model effectors, we report that while substituting the conserved Trp with Ala abolished activity, conservative Trp to Tyr or Glu to Asp substitutions did not affect stress-fibre formation. We show, using dominant negative constructs and chemical inhibitors, that the activity of EspM2 and EspM3 is RhoA and ROCK-dependent. Using Rhotekin pull-downs, we have shown that EspM2 and EspM3 activate RhoA; translocation of EspM2 and EspM3 triggered phosphorylation of cofilin. These results suggest that the EspM effectors modulate actin dynamics by activating the RhoA signalling pathway

COMPARISON OF ACTIVITY CONCENTRATIONS OF NATURAL RADIONUCLIDES IN SOILS COLLECTED AT DIFFERENT DEPTHS OF SELECTED HAND-DUG WELLS IN ABEOKUTA

This study was aimed at measuring and comparing the activity concentration of soil samples collected from some selected hand – dug wells with their corresponding depths of collection in Abeokuta metropolis. Total of twenty (20) soil samples were collected from hand-dug wells in five sites (Obada, Adigbe, Kuto, Olorunsogo, and Obantoko) within Abeokuta with four (4) soil samples from each hand-dug well at the surface, (0.0m) through to 2.25m depth. Gamma ray spectroscopy with High Purity Germanium (HPGe) detector was used for the measurements. The average activity concentrations obtained for the three natural radionuclides 226Ra, 232Th and 40K in Bq/Kg are 34.31 ± 2.01, 128.73 ± 4.41 and 152.31 ± 2.59 respectively at depth 0.00 m (surface), 23.00 ± 1.61, 68.39 ± 3.24 and 191.08 ± 3.11 respectively at depth 0.75 m, 31.52 ± 2.21, 145.37± 4.95 and 375.56 ± 5.50 respectively at 1.50 m and lastly 28.57±1.70, 95.61 ± 3.71 and 181.10 ± 3.94 respectively at 2.25 m depth. The world average activity concentrations for 226Ra, 232Th and 40K are given to be 35 Bqkg-1, 30 Bqkg-1 and 400 Bqkg-1 respectively (UNSCEAR 2000). 232Th showed  higher average values than the world’s average while averages of 226Ra and 40K were lower but most of the activity concentration values obtained in some of the locations are higher than the world’s average values, especially 226Raand 232Th in the soil samples.