Cooling a nanomechanical resonator with quantum back-action

Quantum mechanics demands that the act of measurement must affect the measured object. When a linear amplifier is used to continuously monitor the position of an object, the Heisenberg uncertainty relationship requires that the object be driven by force impulses, called back-action. Here we measure the back-action of a superconducting single-electron transistor (SSET) on a radiofrequency nanomechanical resonator. The conductance of the SSET, which is capacitively coupled to the resonator, provides a sensitive probe of the latter's position;back-action effects manifest themselves as an effective thermal bath, the properties of which depend sensitively on SSET bias conditions. Surprisingly, when the SSET is biased near a transport resonance, we observe cooling of the nanomechanical mode from 550mK to 300mK-- an effect that is analogous to laser cooling in atomic physics. Our measurements have implications for nanomechanical readout of quantum information devices and the limits of ultrasensitive force microscopy (such as single-nuclear-spin magnetic resonance force microscopy). Furthermore, we anticipate the use of these backaction effects to prepare ultracold and quantum states of mechanical structures, which would not be accessible with existing technology.Comment: 28 pages, 7 figures; accepted for publication in Natur

Social Relationships and Mortality Risk: A Meta-analytic Review

In a meta-analysis, Julianne Holt-Lunstad and colleagues find that individuals' social relationships have as much influence on mortality risk as other well-established risk factors for mortality, such as smoking

Rapporteur summaries of plenary, symposia, and oral sessions from the XXIIIrd World Congress of Psychiatric Genetics Meeting in Toronto, Canada, 16-20 October 2015

The XXIIIrd World Congress of Psychiatric Genetics meeting, sponsored by the International Society of Psychiatric Genetics, was held in Toronto, ON, Canada, on 16-20 October 2015. Approximately 700 participants attended to discuss the latest state-of-the-art findings in this rapidly advancing and evolving field. The following report was written by trainee travel awardees. Each was assigned one session as a rapporteur. This manuscript represents the highlights and topics that were covered in the plenary sessions, symposia, and oral sessions during the conference, and contains major notable and new findings. © 2016 Wolters Kluwer Health, Inc

Summaries from the XIX World Congress of Psychiatric Genetics, Washington, DC, September 10-14, 2011.

The XVIII World Congress of Psychiatric Genetics (WCPG), sponsored by The International Society of Psychiatric Genetics (ISPG) took place in Washington, DC on September 10\u201314, 2011. Approximately 540 participants gathered to discuss the latest findings in this rapidly advancing field. The topics covered can be subdivided into the following categories: the latest results from Genome-Wide Association Studies (GWAS) examining the effects of common allele variation, the new focus on sequencing studies, other genomic mechanisms that include epigenetic gene modification and rare copy number variations, biologic and other endophenotypes, the genetics of post-traumatic stress disorder, substance abuse, gene functioning, pharmacogenomics, and other miscellaneous topics of genetic interest. Some notable reported findings introduced at this congress included: several new or replicated associations for common alleles in GWAS for schizophrenia (a SNP located near the hyaluronan binding protein 2 gene (HABP2) on chromosome 10, an SNP in the Transmembrane protein 45B gene (TMEM45B) on chromosome 11, some popular schizophrenia candidate genes, TCF4, NOTCH4, ZNF804A, and the MHC region replicated, and several novel genes reported, POM121L2, AS3MT, CNNM2, NT5C2; for major depression, the neuronal transporter gene SLC6A15; for bipolar disorder, TRANK1 gene, as well as LMAN2L, PTGFR and the SYNE1 gene encoding Nesprin. Some initial exome sequencing results were reported, but very preliminary, although promising. Endophenotypes that specifically were discussed included amygdala volume and prefrontal cortex activation, suicidal behavior, and impulsivity. There was a large emphasis on nicotine dependence in the substance abuse sessions and an association between smoking quantity and genetic loci on the chromosome 15q25 region was clearly demonstrated. The GABRA2 association to alcohol dependence was confirmed. There were several presentations of candidate gene polymorphisms associated with antidepressant and mood stabilizer response from large pharmacological treatment trials, but no one finding was confirmed and to be definitive yet to be able to be used commercially in the clinic. The complete report summarizing the findings reported at this meeting was written by junior travel awardees, as well as other individuals in training who were volunteers from meeting attendees. Each was assigned sessions as rapporteurs. The entire manuscript represents topics covered in oral presentations during the conference and can be found on line as a journal supplement. It is clear from this 2011 congress that multi-international collaborative efforts to solve the genetic tendency for all major psychiatric disorders are necessary and underway. It is impressive to find that the field has come together in such a collegial fashion in order to make progress toward alleviating the suffering of people with mental illnesses. It is now important to be able to decipher which if any of the accumulating findings are ready for communication to clinicians and implementation clinically. Ethical considerations to their use in treatment of patients will be a continuing ongoing discussion

Frontal midline theta reflects individual task Performance in a working memory task

Frontal midline (fm-)theta activity has been related to working memory (WM) processes, as it typically increases with WM load. The robustness of this effect, however, varies across studies and subjects, putting limits to its interpretation. We hypothesized that variation in the fm-theta effect may reflect individual differences in task difficulty with increasing WM load as indicated by behavioural responses. We further tested whether effects in the alpha range are robust markers of WM load. We recorded 64-channel EEG from 24 healthy adults while they memorized either 2 or 4 unfamiliar symbols (low vs. high WM load) in a modified Sternberg task. The last 2 s of the retention phase were analyzed for WM load-related changes in the theta (5-7 Hz) and alpha range (lower: 8-10 Hz, upper: 10.5-12.5 Hz). Higher WM load led to less accurate and slower responses. The increase of fm-theta with WM load was most pronounced at fm electrodes, localized to anterior cingulate regions, and correlated with the participants' decrease in accuracy due to higher WM load. Alpha peak frequency increased in the high compared to the low WM load condition, corresponding to a decrease in lower alpha range across all channels. The results demonstrate that previously reported variation in fm-theta workload effects can partly be explained by variation in task difficulty indexed by individual task accuracy. Moreover, the results also demonstrate that alpha WM load effects are prominent when separating upper and lower alpha