Indistinguishable Particles in Quantum Mechanics: An Introduction

In this article, we discuss the identity and indistinguishability of quantum systems and the consequent need to introduce an extra postulate in Quantum Mechanics to correctly describe situations involving indistinguishable particles. This is, for electrons, the Pauli Exclusion Principle, or in general, the Symmetrization Postulate. Then, we introduce fermions and bosons and the distributions respectively describing their statistical behaviour in indistinguishable situations. Following that, we discuss the spin-statistics connection, as well as alternative statistics and experimental evidence for all these results, including the use of bunching and antibunching of particles emerging from a beam splitter as a signature for some bosonic or fermionic states.Comment: To appear in Contemp. Phy

Bax ratio in advanced epithelial ovarian cancer

Kruppel-like factor 4 (KLF4) is a key transcriptional regulator of cell differentiation and proliferation and an altered expression of KLF4 has been reported in a number of human malignancies. In the present study, we investigated KLF4 expression and its role in cell proliferation in advanced epithelial ovarian cancer (FOC). We compared KLF4, Bcl-2 and Bax transcript levels in ovaries isolated from advanced EOC and normal control ovaries. In addition, the KLF4 gene was transduced into ovarian cancer cells and transcript levels of Bcl-2 and Bax and cell proliferation were analyzed by real-time RT-PCR and MTT assays, respectively. Ovarian KLF4 expression and Bcl-2/Bax ratios were downregulated in most cases of advanced EOC. In addition, KLF4 overexpression in ovarian cancer cells increased the Bcl-2/Bax ratio. However, MTT analysis indicated that the overexpression of KLF4 had no effect on the proliferation of ovarian cancer cells. The inactivation of KLF4 is frequently observed in ovarian cancers and a reduced expression of KLF4 in the ovarian cancers may lead to a reduction in the Bcl-2/Bax ratio. The latter has a role in predicting cancer grade, although its exact role in ovarian carcinogenesis requires clarification.We thank Professor Hyun Kook (Medical Research Center for Gene Regulation, Chonnam National University Medical School, Gwangju, Korea) for the gift of the pCMV3-FLAG-KLF4 plasmid construct. This study was supported by a Korea Research Foundation Grant funded by the Korean Government (KRF 2009-0074679 and 2009-0065769)

Wait a second: brief delays in responding reduce focality effects in event-based prospective memory

Remembering to perform deferred actions when an event is encountered in the future is referred to as event-based prospective memory (PM). We examined whether the failure of individuals to allocate sufficient attentional resources to nonfocal PM tasks can be linked to the response demands inherent in PM paradigms that require the PM task to race for response selection with the speeded ongoing task. In three experiments, participants performed a lexical decision task while being required to make a separate PM response to a specific word (focal), an exemplar of a category (nonfocal), or a syllable (nonfocal). We manipulated the earliest time participants could make task responses by presenting a tone at varying onsets (0-1,600 ms) following stimulus presentation. Improvements in focal PM and nonfocal PM were observed at response delays as brief as 200 ms and 400 ms, respectively. Nonfocal PM accuracy was comparable to focal PM accuracy at delays of 600 ms and 1,600 ms for categorical targets and syllable targets, respectively. Delaying task responses freed the resource-demanding processing operations used on the ongoing task for use on the nonfocal PM task, increasing the probability that the nonfocal PM features of ongoing task stimuli were adequately assessed prior to the ongoing task response

Prospective memory and ageing paradox with event-based tasks : A study of young, young-old, and old-old participants

Research on ageing and prospective memory—remembering to do something in the future—has resulted in paradoxical findings, whereby older adults are often impaired in the laboratory but perform significantly better than younger adults in naturalistic settings. Nevertheless, there are very few studies that have examined prospective memory both in and outside the laboratory using the same sample of young and old participants. Moreover, most naturalistic studies have used time-based tasks, and it is unclear whether the prospective memory and ageing paradox extends to event-based tasks. In this study, 72 young (18–30 years), 79 young-old (61–70 years), and 72 old-old (71–80 years) participants completed several event-based tasks in and outside the laboratory. Results showed that the ageing paradox does exist for event-based tasks but manifests itself differently from that in time-based tasks. Thus, younger adults outperformed old-old participants in two laboratory event-based tasks, but there were no age effects for a naturalistic task completed at home (remembering to write the date and time in the upper left corner of a questionnaire). The young and old-old also did not differ in remembering to retrieve a wristwatch from a pocket at the end of the laboratory session. This indicates that the paradox may be due to differences in ongoing task demands in the lab and everyday life, rather than the location per se. The findings call for a concentrated effort towards a theory of cognitive ageing that identifies the variables that do, or do not, account for this paradoxPeer reviewedSubmitted Versio

Diffusion Tensor Imaging of Incentive Effects in Prospective Memory after Pediatric Traumatic Brain Injury

Few studies exist investigating the brain-behavior relations of event-based prospective memory (EB-PM) impairments following traumatic brain injury (TBI). To address this, children with moderate-to-severe TBI performed an EB-PM test with two motivational enhancement conditions and underwent concurrent diffusion tensor imaging (DTI) at 3 months post-injury. Children with orthopedic injuries (OI; n = 37) or moderate-to-severe TBI (n = 40) were contrasted. Significant group differences were found for fractional anisotropy (FA) and apparent diffusion coefficient for orbitofrontal white matter (WM), cingulum bundles, and uncinate fasciculi. The FA of these WM structures in children with TBI significantly correlated with EB-PM performance in the high, but not the low motivation condition. Regression analyses within the TBI group indicated that the FA of the left cingulum bundle (p = 0.003), left orbitofrontal WM (p < 0.02), and left (p < 0.02) and right (p < 0.008) uncinate fasciculi significantly predicted EB-PM performance in the high motivation condition. We infer that the cingulum bundles, orbitofrontal WM, and uncinate fasciculi are important WM structures mediating motivation-based EB-PM responses following moderate-to-severe TBI in children