Maladaptive bias for extrahippocampal navigation strategies in aging humans.

Efficient spatial navigation requires not only accurate spatial knowledge but also the selection of appropriate strategies. Using a novel paradigm that allowed us to distinguish between beacon, associative cue, and place strategies, we investigated the effects of cognitive aging on the selection and adoption of navigation strategies in humans. Participants were required to rejoin a previously learned route encountered from an unfamiliar direction. Successful performance required the use of an allocentric place strategy, which was increasingly observed in young participants over six experimental sessions. In contrast, older participants, who were able to recall the route when approaching intersections from the same direction as during encoding, failed to use the correct place strategy when approaching intersections from novel directions. Instead, they continuously used a beacon strategy and showed no evidence of changing their behavior across the six sessions. Given that this bias was already apparent in the first experimental session, the inability to adopt the correct place strategy is not related to an inability to switch from a firmly established response strategy to an allocentric place strategy. Rather, and in line with previous research, age-related deficits in allocentric processing result in shifts in preferred navigation strategies and an overall bias for response strategies. The specific preference for a beacon strategy is discussed in the context of a possible dissociation between beacon-based and associative-cue-based response learning in the striatum, with the latter being more sensitive to age-related changes

Identifying studies for systematic reviews - An example from medical imaging

Objectives: To determine if published figures on the proportion of articles included in systematic reviews and identified in electronic databases are applicable to an example from medical imaging. Methods: A systematic review was performed. Additionally, sensitivity and precision of a MEDLINE search were compared with values from three published searches, each customized for a specific field. Results: All articles included in the systematic review were in electronic databases. The MEDLINE search had low precision compared with searches in other fields. Conclusions: in a specific area of medical imaging, electronic databases, including MEDLINE, are reliable sources of articles

QCD-supression by Black Hole Production at the LHC

Possible consequences of the production of small black holes at the LHC for different scenarios with large extra dimensions are investigated. The effects from black hole production on some standard jet observables are examined, concentrating on the reduction of the QCD cross section. It is found that black hole production of partons interacting on a short enough distance indeed seem to generate a drastic drop in the QCD cross section. However from an experimental point of view this will in most cases be camouflaged by energetic radiation from the black holes

Studies On The Reduction Of β-enamino Ketones

Reduction of β-enamino ketones 1 with NaBH(OAc)3 in glacial acetic acid gave β-amino ketones 3 in 65% to 67% yield. These data and others observed in the reduction of β-enamino ketones 1 to preferentially syn γ-amino alcohols 2 with NaBH4/HOAc suggest that in this last reaction we have firstly the reduction of the β-enamino ketones 1 to produce the β-amino ketones 3, and then this compound is reduced to the γ-amino alcohols 2. We can say from this results that the diastereosselectivity of the reduction of β-enamino ketones 1 to mainly syn γ-amino álcohols 2, can be analysed as a competition between a chair-like transition state and a boat-like transition state, obtained from the β-amino ketones 3. © 2006 Sociedade Brasileira de Química.17714401442Harris, M.I.N.C., Braga, A.C.H., (2004) J. Braz. Chem. Soc., 15, p. 971Harris, M.I.N.C., (1993), Ph.D. Thesis, Universidade Estadual de Campinas, BrazilBraga, A. C. H.Harris, M. I. N. C.Br PI 9.502.467-0, 1995. (CA 128:243740)Gribble, G.W., Nutaitis, C.F., (1985) Org. Prep. Proced. Int., 17, p. 317Gribble, G.W., (1998) Chem. Soc. Rev., 27, p. 395For a better understanding of this reactivity, theoretical studies are in progressnoteMarchini, P., Liso, G., Reho, A., (1975) J. Org. Chem., 40, p. 3453Evans, D.A., Chapman, K.T., Carreira, E.M., (1988) J. Am. Chem. Soc., 110, p. 3560Palmieri, G., Cimarelli, C., (2006) Arkivoc, p. 10

Pengkajian nilai-nilai luhur budaya spiritual bangsa Daerah Istimewa Yogyakarta II

Nilai-nilai luhur budaya spiritual mempunyai dimensi luas dan ada kaitannya dengan sistem kepercayaan yang dibentuk oleh suatu keyakinan dan kaidah nilai-nilai budaya yang dipengaruhi oleh kondisi dan situasi setempat. Seperti misalnya lingkungan geografis. Situasi dan kondisi semacam ini menjadikan masyarakat Indonesia dapat dan mampu mengembangkan dan mempertahankan nilai-nilai kebudayaan sendiri. Dalam pengkajian ini sasarannya wilayah Daerah Istimewa Yogyakarta, terbagi menjadi 4 (empat) Daerah Tingkat 11/Kabupaten, yaitu Kabupaten Bantul, Kabupaten Gunung Kidul, Kabupaten Kulon Progo, dan Kabupaten Sleman serta I (satu) Kotamadya Yogyakarta

Nonuniversality in the pair contact process with diffusion

We study the static and dynamic behavior of the one dimensional pair contact process with diffusion. Several critical exponents are found to vary with the diffusion rate, while the order-parameter moment ratio m=\bar{rho^2} /\bar{rho}^2 grows logarithmically with the system size. The anomalous behavior of m is traced to a violation of scaling in the order parameter probability density, which in turn reflects the presence of two distinct sectors, one purely diffusive, the other reactive, within the active phase. Studies restricted to the reactive sector yield precise estimates for exponents beta and nu_perp, and confirm finite size scaling of the order parameter. In the course of our study we determine, for the first time, the universal value m_c = 1.334 associated with the parity-conserving universality class in one dimension.Comment: 9 pages, 5 figure

Neutron EDM from Electric and Chromoelectric Dipole Moments of Quarks

Using QCD sum rules, we calculate the electric dipole moment of the neutron d_n induced by all CP violating operators up to dimension five. We find that the chromoelectric dipole moments of quarks \tilde d_i, including that of the strange quark, provide significant contributions comparable in magnitude to those induced by the quark electric dipole moments d_i. When the theta term is removed via the Peccei-Quinn symmetry, the strange quark contribution is also suppressed and d_n =(1\pm 0.5)[1.1e(\tilde d_d + 0.5\tilde d_u)+1.4(d_d-0.25d_u)].Comment: 4 pages, revtex, v2: missing overall factor of two reinstate