Stability of Magneto-optical Traps with Large Field Gradients: Limits on the Tight Confinement of Single Atoms

We report measurements of the stability of magneto-optical traps (MOTs) for neutral atoms in the limit of tight confinement of a single atom. For quadrupole magnetic field gradients at the trap center greater than ∼1 kG/cm, we find that stochastic diffusion of atoms out of the trapping volume becomes the dominant particle loss mechanism, ultimately limiting the MOT size to greater than ∼5 μm. We measured and modeled the diffusive loss rate as a function of laser power, detuning, and field gradient for trapped cesium atoms. In addition, for as few as two atoms, the collisional loss rates become very high for tightly confined traps, allowing the direct observation of isolated two-body atomic collisions in a MOT

Ipsilateral breast tumour relapse: local recurrence versus new primary and the effect of whole breast radiotherapy on the rate of new primaries

PurposeThe justification for partial breast radiotherapy after breast conservation surgery assumes that ipsilateral breast tumor relapses (IBTR) outside the index quadrant are mostly new primary (NP) tumors that develop despite radiotherapy. We tested the hypothesis that whole-breast radiotherapy (WBRT) is ineffective in preventing NP by comparing development rates in irradiated and contralateral breasts after tumor excision and WBRT.Methods and MaterialsWe retrospectively reviewed 1,410 women with breast cancer who were entered into a prospective randomized trial of radiotherapy fractionation and monitored annually for ipsilateral breast tumor relapses (IBTR) and contralateral breast cancer (CLBC). Cases of IBTR were classified into local recurrence (LR) or NP tumors based on location and histology and were subdivided as definite or likely depending on clinical data. Rates of ipsilateral NP and CLBC were compared over a 15-year period of follow-up.ResultsAt a median follow-up of 10.1 years, there were 150 documented cases of IBTR: 118 (79%) cases were definite or likely LR; 27 (18%) cases were definite or likely NP; and 5 (3%) cases could not be classified. There were 71 cases of CLBC. The crude proportion of definite-plus-likely NP was 1.9% (27/1,410) patients compared with 5% (71/1,410) CLBC patients. Cumulative incidence rates at 5, 10, and 15 years were 0.8%, 2.0%, and 3.5%, respectively, for definite-plus-likely NP and 2.4%, 5.8%, and 7.9%, respectively for CLBC, suggesting a difference in the rates of NP and CLBC.ConclusionsThis analysis suggests that WBRT reduces the rate of ipsilateral NP tumors. The late presentation of NP has implications for the reporting of trials that are testing partial breast radiotherapy

A Bio-Logical Theory of Animal Learning

This article provides the foundation for a new predictive theory of animal learning that is based upon a simple logical model. The knowledge of experimental subjects at a given time is described using logical equations. These logical equations are then used to predict a subject’s response when presented with a known or a previously unknown situation. This new theory suc- cessfully anticipates phenomena that existing theories predict, as well as phenomena that they cannot. It provides a theoretical account for phenomena that are beyond the domain of existing models, such as extinction and the detection of novelty, from which “external inhibition” can be explained. Examples of the methods applied to make predictions are given using previously published results. The present theory proposes a new way to envision the minimal functions of the nervous system, and provides possible new insights into the way that brains ultimately create and use knowledge about the world

Delivery status of the ELI-NP gamma beam system

International audienceThe ELI-NP GBS is a high intensity and monochromatic gamma source under construction in Magurele (Romania). The design and construction of the Gamma Beam System complex as well as the integration of the technical plants and the commissioning of the overall facility, was awarded to the Eurogammas Consortium in March 2014. The delivery of the facility has been planned in for 4 stages and the first one was fulfilled in October 31st 2015. The engineering aspects related to the delivery stage 1 are presented

Dynamical model of sequential spatial memory: winnerless competition of patterns

We introduce a new biologically-motivated model of sequential spatial memory which is based on the principle of winnerless competition (WLC). We implement this mechanism in a two-layer neural network structure and present the learning dynamics which leads to the formation of a WLC network. After learning, the system is capable of associative retrieval of pre-recorded sequences of spatial patterns.Comment: 4 pages, submitted to PR

Long-Term Potentiation: One Kind or Many?

Do neurobiologists aim to discover natural kinds? I address this question in this chapter via a critical analysis of classification practices operative across the 43-year history of research on long-term potentiation (LTP). I argue that this 43-year history supports the idea that the structure of scientific practice surrounding LTP research has remained an obstacle to the discovery of natural kinds

Positivity of the English language

Over the last million years, human language has emerged and evolved as a fundamental instrument of social communication and semiotic representation. People use language in part to convey emotional information, leading to the central and contingent questions: (1) What is the emotional spectrum of natural language? and (2) Are natural languages neutrally, positively, or negatively biased? Here, we report that the human-perceived positivity of over 10,000 of the most frequently used English words exhibits a clear positive bias. More deeply, we characterize and quantify distributions of word positivity for four large and distinct corpora, demonstrating that their form is broadly invariant with respect to frequency of word use.Comment: Manuscript: 9 pages, 3 tables, 5 figures; Supplementary Information: 12 pages, 3 tables, 8 figure

Annealing-Dependent Magnetic Depth Profile in Ga[1-x]Mn[x]As

We have studied the depth-dependent magnetic and structural properties of as-grown and optimally annealed Ga[1-x]Mn[x]As films using polarized neutron reflectometry. In addition to increasing total magnetization, the annealing process was observed to produce a significantly more homogeneous distribution of the magnetization. This difference in the films is attributed to the redistribution of Mn at interstitial sites during the annealing process. Also, we have seen evidence of significant magnetization depletion at the surface of both as-grown and annealed films.Comment: 5 pages, 3 figure