Nonlinear Dynamics of a Bose-Einstein Condensate in a Magnetic Waveguide

We have studied the internal and external dynamics of a Bose-Einstein condensate in an anharmonic magnetic waveguide. An oscillating condensate experiences a strong coupling between the center of mass motion and the internal collective modes. Due to the anharmonicity of the magnetic potential, not only the center of mass motion shows harmonic frequency generation, but also the internal dynamics exhibit nonlinear frequency mixing. We describe the data with a theoretical model to high accuracy. For strong excitations we test the experimental data for indications of a chaotic behavior.Comment: 4 pages, 4 figure

Calibration of a single atom detector for atomic micro chips

We experimentally investigate a scheme for detecting single atoms magnetically trapped on an atom chip. The detector is based on the photoionization of atoms and the subsequent detection of the generated ions. We describe the characterization of the ion detector with emphasis on its calibration via the correlation of ions with simultaneously generated electrons. A detection efficiency of 47.8% (+-2.6%) is measured, which is useful for single atom detection, and close to the limit allowing atom counting with sub-Poissonian uncertainty

An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(epsilon-caprolactone)

Additive manufacturing or 3D printing as an umbrella term for various materials processing methods has distinct advantages over many other processing methods, including the ability to generate highly complex shapes and designs. However, the performance of any produced part not only depends on the material used and its shape, but is also critically dependent on its surface properties. Important features, such as wetting or fouling, critically depend mainly on the immediate surface energy. To gain control over the surface chemistry post-processing modifications are generally necessary, since it' s not a feature of additive manufacturing. Here, we report on the use of initiator and catalyst-free photografting and photopolymerization for the hydrophilic modification of microfiber scaffolds obtained from hydrophobic medical-grade poly(epsilon-caprolactone) via melt-electrowriting. Contact angle measurements and Raman spectroscopy confirms the formation of a more hydrophilic coating of poly(2-hydroxyethyl methacrylate). Apart from surface modification, we also observe bulk polymerization, which is expected for this method, and currently limits the controllability of this procedure.Peer reviewe

Indium joints for cryogenic gravitational wave detectors

A viable technique for the preparation of highly thermal conductive joints between sapphire components in gravitational wave detectors is presented. The mechanical loss of such a joint was determined to be as low as 2 × 10−3 at 20 K and 2 × 10−2 at 300 K. The thermal noise performance of a typical joint is compared to the requirements of the Japanese gravitational wave detector, KAGRA. It is shown that using such an indium joint in the suspension system allows it to operate with low thermal noise. Additionally, results on the maximum amount of heat which can be extracted via indium joints are presented. It is found that sapphire parts, joined by means of indium, are able to remove the residual heat load in the mirrors of KAGRA

Measurement of the optical absorption of bulk silicon at cryogenic temperature and the implication for the Einstein Telescope

International audienceWe report in this article on the measurement of the optical absorption of moderately doped crystalline silicon samples at 1550 nm, which is a candidate material for the main optics of the low temperature interferometer of the Einstein Telescope (ET). We observe a nearly constant absorption from room temperature down to cryogenic temperatures for two silicon samples presenting an optical absorption of 0.029 cm −1 and 780 ppm cm −1 , both crystals doped with boron. This is in contradiction to what was assumed previously—a negligible optical absorption at low temperature due to the carrier freezeout. As the main consequence, if the silicon intrinsic absorption can not be lowered , the cross section of the mirror suspension of the ET must be increased to be able to carry away the excess heat generated by the partially absorbed laser beam during the operation of the interferometer

Mutants of the Drosophila ncd microtubule motor protein cause centrosomal and spindle pole defects in mitosis

Nonclaret disjunctional (ncd) is a kinesin-related microtubule motor protein required for meiotic and early mitotic chromosome distribution in Drosophila. ncd translocates on microtubules with the opposite polarity to kinesin, toward microtubule minus ends, and is associated with spindles in chromosome/spindle preparations. Here we report a new mutant of ncd caused by partial deletion of the predicted coiled-coil central stalk. The mutant protein exhibits a velocity of translocation and ability to generate torque in motility assays comparable to near full-length ncd, but only partially rescues a null mutant for chromosome mis-segregation. Antibody staining experiments show that the partial loss-of-function and null mutants cause centrosomal and spindle pole defects, including centrosome splitting and loss of centrosomes from spindle poles, and localize ncd to centrosomes as well as spindles of wild-type embryos. Association of ncd with spindles and centrosomes is microtubule- and cell cycle-dependent: inhibition of microtubule assembly with colchicine abolishes ncd staining and centrosomal staining is observed in prometaphase, metaphase and anaphase, but diminishes in late anaphase/telophase. The cell cycle dependence of centrosomal staining and the defects of mutants provide clear evidence for activity of the ncd motor protein near or at the spindle poles in mitosis. The ncd motor may interact with centrosomal microtubules and spindle fibers to attach centrosomes to spindle poles, and mediate poleward translocation (flux) of kinetochore fibers, a process that may underlie poleward movement of chromosomes in mitosis. Together with previous work, our findings indicate that ncd is important in maintaining spindle poles in mitosis as well as in meiosis

Association between social support and place of delivery: a cross-sectional study in Kericho, Western Kenya

Background: An estimated 358,000 maternal deaths still occur worldwide each year. The place of delivery is of great significance to the reduction of maternal mortality. Moreover, socio-economic factors, cultural traits, and local customs are associated with health-seeking behavior. This study aimed to explore determinants of association between social support and place of delivery. Methods: This cross-sectional study was conducted from September to November 2011 at Sosiot Health Center, Kericho West District, Kenya. Participants were 303 mothers who brought their babies to the health center for immunization within their first year of life. Women underwent a structured interview using a questionnaire on demographic characteristics and their experiences of delivery including place of delivery and social support. Results: The proportion of deliveries at health facilities was significantly higher in unmarried than married women (93% and 78%, respectively; P = 0.008). Unmarried women whose mothers supported them in housework and whose sisters helped them fetch water were more likely to deliver at health facilities (P = 0.002 and 0.042, respectively) than those without this support. However, married women whose husbands supported them in farming and whose neighbors helped them fetch water were less likely to deliver at health facilities (P = 0.003 and 0.021, respectively) than those without this support. Married women who were advised to deliver at a health facility by their mother-in-law or health staff were more likely to deliver at health facilities (P = 0.015 and 0.022, respectively) than those who did not receive this advice. Multivariate analysis revealed that married women were more likely to deliver at health facilities if they were highly educated (odds ratio [OR] = 2.5); had financial capability (OR = 4.3); had medical insurance (OR = 4.2); were primiparous (OR = 3.5); did not have the support of sisters-in-law for fetching water (OR = 2.2); or were advised to deliver at a health facility by family or neighbors (OR = 2.5).Conclusions: Promotion of delivery at health facilities requires approaches that consider women\u27s social situation, since factors influencing place of delivery differ for married and unmarried women