1,032 research outputs found
Adolescents, Adults and Rewards: Comparing Motivational Neurocircuitry Recruitment Using fMRI
Background: Adolescent risk-taking, including behaviors resulting in injury or death, has been attributed in part to maturational differences in mesolimbic incentive-motivational neurocircuitry, including ostensible oversensitivity of the nucleus accumbens (NAcc) to rewards. Methodology/Principal Findings: To test whether adolescents showed increased NAcc activation by cues for rewards, or by delivery of rewards, we scanned 24 adolescents (age 12–17) and 24 adults age (22–42) with functional magnetic resonance imaging while they performed a monetary incentive delay (MID) task. The MID task was configured to temporally disentangle potential reward or potential loss anticipation-related brain signal from reward or loss notification-related signal. Subjects saw cues signaling opportunities to win or avoid losing .50, or $5 for responding quickly to a subsequent target. Subjects then viewed feedback of their trial success after a variable interval from cue presentation of between 6 to17 s. Adolescents showed reduced NAcc recruitment by reward-predictive cues compared to adult controls in a linear contrast with non-incentive cues, and in a volume-of-interest analysis of signal change in the NAcc. In contrast, adolescents showed little difference in striatal and frontocortical responsiveness to reward deliveries compared to adults. Conclusions/Significance: In light of divergent developmental difference findings between neuroimaging incentive paradigms (as well as at different stages within the same task), these data suggest that maturational differences i
Multifunctional Devices and Logic Gates With Undoped Silicon Nanowires
We report on the electronic transport properties of multiple-gate devices
fabricated from undoped silicon nanowires. Understanding and control of the
relevant transport mechanisms was achieved by means of local electrostatic
gating and temperature dependent measurements. The roles of the source/drain
contacts and of the silicon channel could be independently evaluated and tuned.
Wrap gates surrounding the silicide-silicon contact interfaces were proved to
be effective in inducing a full suppression of the contact Schottky barriers,
thereby enabling carrier injection down to liquid-helium temperature. By
independently tuning the effective Schottky barrier heights, a variety of
reconfigurable device functionalities could be obtained. In particular, the
same nanowire device could be configured to work as a Schottky barrier
transistor, a Schottky diode or a p-n diode with tunable polarities. This
versatility was eventually exploited to realize a NAND logic gate with gain
well above one.Comment: 6 pages, 5 figure
Motor Preparatory Activity in Posterior Parietal Cortex is Modulated by Subjective Absolute Value
For optimal response selection, the consequences associated with behavioral success or failure must be appraised. To determine how monetary consequences influence the neural representations of motor preparation, human brain activity was scanned with fMRI while subjects performed a complex spatial visuomotor task. At the beginning of each trial, reward context cues indicated the potential gain and loss imposed for correct or incorrect trial completion. FMRI-activity in canonical reward structures reflected the expected value related to the context. In contrast, motor preparatory activity in posterior parietal and premotor cortex peaked in high “absolute value” (high gain or loss) conditions: being highest for large gains in subjects who believed they performed well while being highest for large losses in those who believed they performed poorly. These results suggest that the neural activity preceding goal-directed actions incorporates the absolute value of that action, predicated upon subjective, rather than objective, estimates of one's performance
The HIBEAM program: search for neutron oscillations at the ESS
With the construction of the European Spallation Source, a remarkable
opportunity has emerged to conduct high sensitivity searches for neutron
oscillations, including a first search for thirty years for free neutrons
converting to antineutrons. Furthermore, searches can be made for transitions
of neutrons and antineutrons to sterile neutron states. The HIBEAM program
provides an increase in sensitivity of an order of magnitude compared to
previous work.
The HIBEAM program corresponds to baryon number violation by one and two
units. The observation of a process satisfying a Sakharov condition addresses
the open question of the origin of the matter-antimatter asymmetry in the
Universe. Sterile neutron states would belong to a `dark' sector of particles
which may explain dark matter. As electrically neutral, meta-stable objects
that can be copiously produced and studied, neutrons represent an attractive
portal to a `dark' sector.
This paper describes the capability, design, infrastructure, and potential of
the HIBEAM program. This includes a dedicated beamline, neutron optical system,
magnetic shielding and control, and detectors for neutrons and antineutrons.Comment: 41 pages, 12 figure
Giant fluctuations and gate control of the g-factor in InAs Nanowire Quantum Dots
We study the g-factor of discrete electron states in InAs nanowire based
quantum dots. The g values are determined from the magnetic field splitting of
the zero bias anomaly due to the spin 1/2-Kondo effect. Unlike to previous
studies based on 2DEG quantum dots, the g-factors of neighboring electron
states show a surprisingly large fluctuation: g can scatter between 2 and 18.
Furthermore electric gate tunability of the g-factor is demonstrated.Comment: 12 pages, 3 figure
Are pediatric Open Access journals promoting good publication practice? An analysis of author instructions
<p>Abstract</p> <p>Background</p> <p>Several studies analyzed whether conventional journals in general medicine or specialties such as pediatrics endorse recommendations aiming to improve publication practice. Despite evidence showing benefits of these recommendations, the proportion of endorsing journals has been moderate to low and varied considerably for different recommendations. About half of pediatric journals indexed in the Journal Citation Report referred to the Uniform Requirements for Manuscripts of the International Committee of Medical Journal Editors (ICMJE) but only about a quarter recommended registration of trials. We aimed to investigate to what extent pediatric open-access (OA) journals endorse these recommendations. We hypothesized that a high proportion of these journals have adopted recommendations on good publication practice since OA electronic publishing has been associated with a number of editorial innovations aiming at improved access and transparency.</p> <p>Methods</p> <p>We identified 41 journals publishing original research in the subject category "Health Sciences, Medicine (General), Pediatrics" of the Directory of Open Access Journals <url>http://www.doaj.org</url>. From the journals' online author instructions we extracted information regarding endorsement of four domains of editorial policy: the Uniform Requirements for Manuscripts, trial registration, disclosure of conflicts of interest and five major reporting guidelines such as the CONSORT (Consolidated Standards of Reporting Trials) statement. Two investigators collected data independently.</p> <p>Results</p> <p>The Uniform Requirements were mentioned by 27 (66%) pediatric OA journals. Thirteen (32%) required or recommended trial registration prior to publication of a trial report. Conflict of interest policies were stated by 25 journals (61%). Advice about reporting guidelines was less frequent: CONSORT was referred to by 12 journals (29%) followed by other reporting guidelines (MOOSE, PRISMA or STARD) (8 journals, 20%) and STROBE (3 journals, 7%). The EQUATOR network, a platform of several guideline initiatives, was acknowledged by 4 journals (10%).</p> <p>Journals published by OA publishing houses gave more guidance than journals published by professional societies or other publishers.</p> <p>Conclusions</p> <p>Pediatric OA journals mentioned certain recommendations such as the Uniform Requirements or trial registration more frequently than conventional journals; however, endorsement is still only moderate. Further research should confirm these exploratory findings in other medical fields and should clarify what the motivations and barriers are in implementing such policies.</p
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Supervised versus unsupervised categorization: Two sides of the same coin?
Supervised and unsupervised categorization have been studied in separate research traditions. A handful of studies have attempted to explore a possible convergence between the two. The present research builds on these studies, by comparing the unsupervised categorization results of Pothos et al. (submitted; 2008) with the results from two procedures of supervised categorization. In two experiments, we tested 375 participants with nine different stimulus sets, and examined the relation between ease of learning of a classification, memory for a classification, and spontaneous preference for a classification. After taking into account the role of the number of category labels (clusters) in supervised learning, we found the three variables to be closely associated with each other. Our results provide encouragement for researchers seeking unified theoretical explanations for supervised and unsupervised categorization, but raise a range of challenging theoretical questions
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