A Developmental Study of Changes in Strategy Selection

The present study focused on the relationship between children\u27s knowledge of appropriate task strategies and actual strategy use on two recall memory tasks and two tasks less demanding of memory--coding and alphabetizing. On the recall memory tasks, attention was specifically directed to the modifications of children\u27s strategies as a function of changing task demands. The subjects consisted of 80 seven-, nine-, 11-, and 15-year olds. The children were shown two sets of pictures on cards, representing three categories, which were later to be recalled. The children were free to manipulate the pictures during all the study periods. Task demand changes included either the study time allowed (30 seconds or 2 minutes) or the number of items to be remembered (12 or 24 pictures). The coding task required that the children copy symbols that corresponded to numbers in the coding key. For the alphabetizing task, children were to put words on cards in alphabetical order within a given amount of time. The data analyses showed that children\u27s knowledge of task relevant strategies closely paralleled their task behavior. Overall, picture recall increased with age and with the type of strategy used

Patterns of hydroxyproline excretion in ovariectomized and estrogen treated rats

If nuclear binding sites for estrogens exist in bone cells, then the origin of estrogen-deficiency-induced osteopenia may be at the level of bone matrix protein synthesis. Since collagen is the most abundant protein in the bone matrix, and since hydroxyproline is an imino acid nearly exclusive to collagen, a monitoring of the metabolism of hydroxyproline in ovariectomized and estrogen treated rats may provide insight into the patterns of estrogen-deficiency-induced osteopenia. The purpose of our study was to test the hypothesis that ovariectomy will increase urinary hydroxyproline excretion in the rat and that this increase will be reversed by estrogen treatment therapy

Immunoregulation of Liver Regeneration by the Aryl Hydrocarbon Receptor: Role of Lymphocytes and Interferon-Gamma

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental contaminant that elicits toxicity by activating the aryl hydrocarbon receptor. The toxic effects associated with TCDD exposure include immunotoxicity and dysregulated cell cycle control, although the mechanisms are poorly understood. A previous report indicates that exposure to TCDD suppresses hepatocyte proliferation in a mouse model of liver regeneration induced by 70% partial hepatectomy (PH). Based on reports that liver regeneration is negatively regulated by interferon (IFN)-γ produced by activated natural killer (NK) cells, along with the well-established immunotoxic effects of TCDD in other model systems, we hypothesized that TCDD treatment attenuates liver regeneration by enhancing NK cell activation and IFN-γ production in the regenerating liver. We also considered the effects of TCDD on natural killer (NK) T and T cells, which are capable of producing IFN-γ as well. Mice were treated with TCDD (20 μg/kg) one day prior to surgical PH. Hepatocyte proliferation in the remnant liver was measured based on the incorporation of a thymidine analog, bromodeoxyuridine. Lymphocytes were collected from the spleen and remnant liver and analyzed by flow cytometry. IFN-γ was measured by intracellular staining followed by flow cytometry. Consistent with other reports, we found that TCDD treatment suppressed hepatocyte proliferation in the regenerating liver by 50-80%. However, contrary to our hypothesis, exposure to TCDD had no effect on the number of lymphocytes in the spleen or liver after PH, nor did it increase IFN-γ+ production by lymphocytes in the regenerating liver. Moreover, exposure to TCDD did not increase the number of NK and NKT cells expressing CD69, an early activation marker. To determine the relevance of NK cells to the TCDD-mediated suppression of liver regeneration, mice were treated with an α-asialo-GM-1 antibody to deplete NK cells prior to TCDD administration and PH. Depletion of NK cells did not restore hepatocyte proliferation in TCDD-treated mice, indicating that NK cells are not required for the attenuation of liver regeneration by TCDD. Hence, exposure to TCDD suppresses in vivo hepatocyte proliferation by a mechanism that does not involve NK cells or enhanced production of IFN-γ

Experimental study of 199Hg spin anti-relaxation coatings

We report on a comparison of spin relaxation rates in a $^{199}$Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating.Comment: 9 pages, 6 figures, submitted to JINS

An Improved Search for the Neutron Electric Dipole Moment

A permanent electric dipole moment of fundamental spin-1/2 particles violates both parity (P) and time re- versal (T) symmetry, and hence, also charge-parity (CP) symmetry since there is no sign of CPT-violation. The search for a neutron electric dipole moment (nEDM) probes CP violation within and beyond the Stan- dard Model. The experiment, set up at the Paul Scherrer Institute (PSI), an improved, upgraded version of the apparatus which provided the current best experimental limit, dn < 2.9E-26 ecm (90% C.L.), by the RAL/Sussex/ILL collaboration: Baker et al., Phys. Rev. Lett. 97, 131801 (2006). In the next two years we aim to improve the sensitivity of the apparatus to sigma(dn) = 2.6E-27 ecm corresponding to an upper limit of dn < 5E-27 ecm (95% C.L.), in case for a null result. In parallel the collaboration works on the design of a new apparatus to further increase the sensitivity to sigma(dn) = 2.6E-28 ecm.Comment: APS Division for particles and fields, Conference Proceedings, Two figure

Testing isotropy of the universe using the Ramsey resonance technique on ultracold neutron spins

Physics at the Planck scale could be revealed by looking for tiny violations of fundamental symmetries in low energy experiments. In 2008, a sensitive test of the isotropy of the Universe using has been performed with stored ultracold neutrons (UCN), this is the first clock-comparison experiment performed with free neutrons. During several days we monitored the Larmor frequency of neutron spins in a weak magnetic field using the Ramsey resonance technique. An non-zero cosmic axial field, violating rotational symmetry, would induce a daily variation of the precession frequency. Our null result constitutes one of the most stringent tests of Lorentz invariance to date.Comment: proceedings of the PNCMI2010 conferenc

Experimental study of 199Hg spin anti-relaxation coatings

We report on a comparison of spin relaxation rates in a 199Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating

Measurement of the permanent electric dipole moment of the neutron

We present the result of an experiment to measure the electric dipole moment EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons (UCN). Our measurement stands in the long history of EDM experiments probing physics violating time reversal invariance. The salient features of this experiment were the use of a Hg-199 co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes. The statistical analysis was performed on blinded datasets by two separate groups while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{\rm n} = (0.0\pm1.1_{\rm stat}\pm0.2_{\rmsys})\times10^{-26}e\,{\rm cm}

A measurement of the neutron to 199Hg magnetic moment ratio

The neutron gyromagnetic ratio has been measured relative to that of the 199Hg atom with an uncertainty of 0.8 ppm. We employed an apparatus where ultracold neutrons and mercury atoms are stored in the same volume and report the result γn/γHg=3.8424574(30)γn/γHg=3.8424574(30)