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At least 91 records · Page 5Linked to original sources
PubMed2004

The African diaspora: mitochondrial DNA and the Atlantic slave trade.

Between the 15th and 19th centuries ad, the Atlantic slave trade resulted in the forced movement of approximately 13 million people from Africa, mainly to the Americas. Only approximately 11 million survived the passage, and many more died in the early years of captivity. We have studied 481 mitochondrial DNAs (mtDNAs) of recent African ancestry in the Americas and in Eurasia, in an attempt to trace them back to particular regions of Africa. Our results show that mtDNAs in America and Eurasia can, in many cases, be traced to broad geographical regions within Africa, largely in accordance with historical evidence, and raise the possibility that a greater resolution may be possible in the future. However, they also indicate that, at least for the moment, considerable caution is warranted when assessing claims to be able to trace the ancestry of particular lineages to a particular locality within modern-day Africa.

Black People↗
PubMed2001

Master-slave synchronization in chaotic discrete-time oscillators.

In this paper, we study a simple discrete-time neural oscillator model that, in certain parameter regimes, exhibits periodic or chaotic dynamics. The present model with intrinsically chaotic dynamics is capable of spatiotemporal information processing: in response to constant external stimulation, the oscillator can switch into different chaotic states restricted to distinct parts of the phase space. Of particular interest is the processing of time-dependent input in a master-slave configuration of two coupled oscillators. Here, the response of an oscillator is studied by driving it with the signal of the other. Following the input, the response system adapts to the state of the drive. For a chaotic drive, we can observe generalized synchronization. The onset of adaptation to the drive state by the response is accompanied by on-off intermittency resulting in irregular bursting behavior.

Journal Article↗
PubMed2003

Unexpected correspondence between noise-induced and master-slave complete synchronizations.

A comparison between noise-induced synchronization and master-slave (Pecora-Carroll) synchronization is investigated in this paper. We find an interesting correspondence between the effective driving variables of these two kinds of synchronizations in three-dimensional chaotic systems, when the systems have nonlinear terms in more than one equation. A study of the Lorenz model, the Hindmarsh-Rose neuron model, and the Hastings-Powell foodweb model is given to support this claim. It is a somewhat surprising result since these two kinds of synchronizations arise through different mechanisms. We also examine an exceptional case, where the nonlinear term of the system appears in a single equation, as in the Pikovsky-Rabinovich circuit model, and explain why the correspondence fails.

Journal Article↗
PubMed2003

The novel MYB protein EARLY-PHYTOCHROME-RESPONSIVE1 is a component of a slave circadian oscillator in Arabidopsis.

Using fluorescent differential display, we identified, from approximately 8000 displayed bands, a DNA fragment showing rapid induction in response to red light irradiation. This EARLY-PHYTOCHROME-RESPONSIVE1 gene (EPR1) encodes a novel nucleus-localized MYB protein harboring a single MYB domain that is highly similar to the circadian oscillator proteins CCA1 and LHY. EPR1 is regulated by both phytochrome A and phytochrome B, and the red-light induction of EPR1 is not inhibited by cycloheximide, demonstrating that EPR1 represents a primary phytochrome-responsive gene. Our results show that EPR1 overexpression results in enhanced far-red light-induced cotyledon opening and delayed flowering. In wild-type Arabidopsis plants grown in continuous light, the EPR1 transcript exhibits circadian rhythmicity similar to that of CCA1 and LHY. Moreover, EPR1 suppresses its own expression, suggesting that this protein is part of a regulatory feedback loop. Constitutive expression of CCA1 and LHY results in the loss of EPR1 rhythmicity, whereas increased levels of EPR1 have no effect on the central oscillator. We propose that EPR1 is a component of a slave oscillator that contributes to the refinement of output pathways, ultimately mediating the correct oscillatory behavior of target genes.

Amino Acid Sequence↗
PubMed2000

Rotation and direction judgment from visual images head-slaved in two and three degrees-of-freedom.

The contribution to spatial awareness of adding a roll degree-of-freedom (DOF) to telepresence camera platform yaw and pitch was examined in an experiment where subjects judged direction and rotation of stationary target markers in a remote scene. Subjects viewed the scene via head-slaved camera images in a head-mounted display. Elimination of the roll DOF affected rotation judgment, but only at extreme yaw and pitch combinations, and did not affect azimuth and elevation judgement. Systematic azimuth overshoot occurred regardless of roll condition. Observed rotation misjudgments are explained by kinematic models for eye-head direction of gaze.

Adult↗
PubMed2006

Virtual reality and a haptic master-slave set-up in post-stroke upper-limb rehabilitation.

Since the number of stroke patients is ever growing, and since studies show that the patients can benefit from more exercise, the possible use of virtual reality and haptic devices in the rehabilitation of stroke patients is researched. Besides offering more independent and challenging exercise possibilities, the inherent registration capabilities of the haptic devices open up the possibility of monitoring patients' motions in an objective way. This research results in the implementation of a VR mock-up of an exercise in which patients use both hands and a stick to push away a ball that is tossed at them. In this mock-up, two FCS HapticMasters are used in a master-slave set-up to mimic the behaviour of the stick. The implementation of the scene shows that there are currently limitations, in the hardware as well as in the software, that cause the virtual exercise to behave differently to the real-life exercise. Consequences for the therapeutic value are subject to further research.

Computer Graphics↗
PubMed1997

[From race to health in Master and slave].

The article analyzes how Gilberto Freyre addresses health-related issues in his book Master and slave. the first point of focus is how the sanitation movement that emerged in the sertão region in the late 1910s influenced Freyre's essay. The article next endeavors to understand the relation between Freyre's emphasis on the problem of syphilis in Brazil and the issues of race and miscegenation, both of which are constants in his works. Lastly, the article endeavors to situate Freyre's ideas within the ideological framework of eugenics that was in fashion in Brazil at the time his works were written.

Brazil↗
PubMedDate not supplied

[A medico-legal problem of the past: invalidation of the sale of a slave in case of concealed disease. Zacchias' opinion].

In his famous "Questions" Paul Zacchias (1584-1659) deals with the medico-legal problem of invalidation of sale of slaves or beasts of burden for concealed redhibitory defects. He analyzes the Roman right always used in his time but does not show any critical mind while he is only compiling and commenting the texts taken from the famous "Edit des Ediles curules". A listing of the redhibitory defects is opposed to the slight vices which do not justify the cancellation of the sale. What is unknown is whether the judge called for a medical appraisal about the reality of the defects, their physical or mental origins, their long-standing development.

Animals↗
PubMed1978

[José Martins da Cruz Jobim: his priority in the detection of an hereditary hematologic disorder in African Negro slaves (author's transl)].

A brazilian physician, José Martins da Cruz Jobim, may be considered the author of one of the earliest medical reports with a story of the prevalence of the sikle cell trait among african negroes who came to Brazil as slaves, by observing their rather remarkable resistance against malarial infections than other sets of our population. Naturally, his report, published in 1835, must be considered by the actual scientific concepts.

Africa↗
PubMed1994

Surgeon James Ramsay, 1733-1789: the Navy and the slave trade.

The end of the American War of Independence in 1783 coincided with two very different, but closely related initiatives: the settlement of New South Wales and the fight against the slave trade. In both, James Ramsay, a naval surgeon, played a decisive role. James Ramsay was born on 25 July 1733 at Fraserburgh on the Aberdeenshire coast. After a grammar school education, he was apprenticed to a Dr Findlay, surgeon and physician in Fraserburgh. Through his proficiency in Latin, he obtained a small bursary which enabled him to enter King's College in the University of Aberdeen and brought Ramsay under the influence of Dr Thomas Reid, the professor of moral philosophy, who exercised a profound influence on Ramsay's thinking (Vol 17, pp 632-3).

History, 18th Century↗
PubMed2003

Masters change, slaves remain.

Sex determination offers an opportunity to address many classic questions of developmental biology. In addition, because sex determination evolves rapidly, it offers an opportunity to investigate the evolution of genetic hierarchies. Sex determination in Drosophila melanogaster is controlled by the master regulatory gene, Sex lethal (Sxl). DmSxl controls the alternative splicing of a downstream gene, transformer (tra), which acts with tra2 to control alternative splicing of doublesex (dsx). DmSxl also controls its own splicing, creating an autoregulatory feedback loop that ensures expression of Sxl in females, but not males. A recent paper has shown that in the dipteran Ceratitis capitata later (downstream) steps in the regulatory hierarchy are conserved, while earlier (upstream) steps are not. Cctra is regulated by alternative splicing and apparently controls the alternative splicing of Ccdsx. However, Cctra is not regulated by CcSxl. Instead it appears to autoregulate in a manner similar to the autoregulation seen with DmSxl.

Animals↗
PubMed1991

Slaving the cytochrome P-450 dependent monooxygenase system by periodically applied light pulses.

The light-induced enhancement of 7-ethoxycoumarin-O-deethylase activity was measured in a reconstituted system consisting of the enzyme P-450 II B1 (P-450PB-B) and the NADPH-cytochrome P-450 reductase. The phases of the catalytic cycle of 2 x 10(12) protein complexes were locked by periodic application of light pulses (0.1 s duration, 1.2-2.5 s repetition time, and 390-470 nm 0.27 Joule/nmol P-450). More than 80% of the active reconstituted enzyme complexes worked in phase if the repetition time (1.32 s) was slightly smaller than the catalytic cycle time of the free running enzyme (1.54 s). The percentage of synchronized enzyme complexes as a function of the repetition time is shown. It is shown that the lifetime of the product-enzyme complex is shortened by the light.

7-Alkoxycoumarin O-Dealkylase↗