Ultrastable Free-Space Laser Links for a Global Network of Optical Atomic Clocks.

A global network of optical atomic clocks will enable unprecedented measurement precision in fields including tests of fundamental physics, dark matter searches, geodesy, and navigation. Free-space laser links through the turbulent atmosphere are needed to fully exploit this global network, by enabling comparisons to airborne and spaceborne clocks. We demonstrate frequency transfer over a 2.4 km atmospheric link with turbulence comparable to that of a ground-to-space link, achieving a fractional frequency stability of 6.1×10^{-21} in 300 s of integration time. We also show that clock comparison between ground and low Earth orbit will be limited by the stability of the clocks themselves after only a few seconds of integration. This significantly advances the technologies needed to realize a global timescale network of optical atomic clocks.

Optimal Imaging of Remote Bodies Using Quantum Detectors.

We implement a general imaging method by measuring the complex degree of coherence using linear optics and photon number resolving detectors. In the absence of collective or entanglement-assisted measurements, our method is optimal over a large range of practically relevant values of the complex degree of coherence. We measure the size and position of a small distant source of pseudothermal light, and show that our method outperforms the traditional imaging method by an order of magnitude in precision. Finally, we show that a lack of photon-number resolution in the detectors has only a modest detrimental effect on measurement precision and simulate imaging using the new and traditional methods with an array of detectors, showing that the new method improves both image clarity and contrast.

Quantum Hypercube States.

We introduce quantum hypercube states, a class of continuous-variable quantum states that are generated as orthographic projections of hypercubes onto the quadrature phase space of a bosonic mode. In addition to their interesting geometry, hypercube states display phase-space features much smaller than Planck's constant, and a large volume of Wigner negativity. We theoretically show that these features make hypercube states sensitive to displacements at extremely small scales in a way that is surprisingly robust to initial thermal occupation and to small separation of the superposed state components. In a high-temperature proof-of-principle optomechanics experiment we observe, and match to theory, the signature outer-edge vertex structure of hypercube states.

Concentration gradient patterns of traffic and non-traffic-generated fine and coarse aerosol particles.

The research project described in this article was undertaken to establish baseline information for a Health Impact Assessment (HIA) project of Interstate 75 road construction in Cincinnati, Ohio. The objective of the authors' study was to evaluate the concentrations of elemental and organic carbon (EC and OC), as well as characterize particle number concentrations using devices that measure the fine fraction in the range of 0.02-1 microm and the coarse fraction up to 20 pm. The measurements were conducted at two sites located in the proximity of an interstate highway (at 124 and 277 m) as well as at a remote control site (at >2000 m from any interstate highway). Samples were collected for 24 hours over 12 days in each season (i.e., summer, fall, and winter). Wind data were obtained from the area weather station. Data were analyzed using mixed linear models. Significant increases in concentrations of EC, OC, and fine particles as well as in EC/OC ratios were observed with decreased distance to the highway; this difference was more pronounced in the fall. These results suggest that residents and workers in areas near high-traffic highways may be exposed to elevated levels of airborne fine particles. The results can be used as a baseline for future HIAs of road construction in the area.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine is a potent mutagen in the mouse small intestine.

Mutations in long lived stem cells are critical events in carcinogenesis. The Dlb-1 assay detects intestinal stem cell mutation at the Dlb-1 locus in Dlb-1a/b heterozygous mice by visualizing mutated clones of epithelial cells in situ which do not bind the lectin Dolichos biflorus agglutinin. We have used this assay to show that the food-derived heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a potent intestinal mutagen when administered either i.p. or p.o. This contrasts with the inactivity of the structurally related mutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in the assay which we have described previously. Immunocytochemical localization of the P-450 enzyme CYP1A2, which is responsible for the primary activation of these mutagens, shows that in untreated mice it is present in liver hepatocytes and in occasional villus epithelial cells but is absent from the target intestinal stem cell population. In addition, liver microsomes, unlike intestinal microsomes, were able to convert PhIP to the proximate mutagen N-hydroxy-PhIP. CYP1A2 immunoreactivity in beta-napthoflavone-induced animals was elevated in liver hepatocytes and increased to a lesser extent in duodenal villus epithelial cells. Treatment with beta-napthoflavone produced an unexpected 46% decrease in the number of Dlb-1 mutations in response to PhIP. Following treatment with PhIP, there was no difference in the number of Dlb-1 locus mutations between the proximal and distal ends of the small intestine in uninduced animals, indicating that the bile duct is unlikely to be responsible for transport of mutation inducing metabolites of PhIP to the small intestine. Our results demonstrate that metabolic activation of an indirect acting genotoxic agent can occur at a site other than the target tissue, and absence of the enzymes required for activation of a mutagen does not necessarily protect that tissue from its genotoxic effects.

p53, mutation frequency and apoptosis in the murine small intestine.

Normal function of the p53 gene is integral to the cellular response to genotoxic stress. One prediction arising from this is that p53 deficiency results in an increased mutation frequency. However, limited evidence has been produced in support of this idea. In order to further investigate the in vivo role of p53 in surveillance against mutation, and particularly to address the significance of p53-dependent apoptosis, we scored mutation frequency at the Dlb-1 locus within cells of the intestinal epithelium of animals which were wild type, heterozygous or null for p53 and heterozygous (a/b) at the Dlb-1 locus. Using this assay we have shown that loss of a p53-dependent apoptotic pathway is associated with the detectable acquisition of mutations, but only at high levels of DNA damage. These results question the significance of the immediate 'wave' of p53-dependent apoptosis seen in this tissue, particularly as there was a delayed p53-independent apoptotic pathway. We conclude that loss of p53 function only becomes relevant to the in vivo acquisition of mutations and thus tumorigenesis in certain circumstances.

Elevated pain threshold in anorexia nervosa subjects.

BACKGROUND: Conflicting data have been published regarding pain threshold in subjects with anorexia nervosa (AN), with some studies indicating elevated pain threshold and others indicating normal thresholds. Previous research has indicated the presence of elevated pain threshold in eating disorder subjects with binge-eating behavior. METHODS: In this study pressure pain detection thresholds (PDT) (assessed by a pressure analgesiometer) in binge-eating/purging and restricting subtypes of AN subjects were compared to control subjects. RESULTS: PDT was elevated in AN compared to control subjects at baseline. There was no difference in PDT between the subgroups of AN subjects. CONCLUSIONS: The etiology of elevated PDT in AN subjects is most likely different from the etiology of elevated PDT in bulimia nervosa subjects.

Construction of cloning/sequencing vectors with an alternative polylinker.

This paper describes the construction of a new plasmid and M13 phage cloning vector in which the 54-bp polylinkers of pUC19 and of M13mp8 are replaced with a 45-bp chemically synthesized polylinker with different restriction sites. The new polylinker is inserted in frame at the N-terminal end of the beta galactosidase lac Z fragment. The plasmid was named pLH1, the phage M13LH1.

Vision influences tactile perception without proprioceptive orienting.

The perception of tactile stimuli is facilitated when subjects look towards the stimulated body site: this facilitation even takes place when visual information is unavailable, as when orienting in the dark. It is not known whether the facilitation is due entirely to such proprioceptive orienting of eye and head, or whether visual information of the body site can also facilitate touch. An experiment is reported which dissociates vision and proprioception, and demonstrates for the first time that vision of a body part, independent of proprioceptive orienting, can indeed effect somatosensation.

How convincing is the evidence for cognitive slowing in Parkinson's disease?

The issue of whether or not Parkinson's disease (PD) patients process information more slowly than normal is unresolved. Across a range of paradigms the evidence for slowing is scant, and many show no slowing. Even the results of a single experimental paradigm can be conflicting; some studies have obtained evidence for slowed memory scanning in subgroups of PD patients whereas others have not. The present study sought the cause of these discrepant results. Old-old (n = 11) and young-old (n = 7) PD subjects and controls (n = 16, n = 9) completed both fixed and varied set versions of the memory scanning task. No evidence for slowing in PD was found. These results indicated that PD did not interact with age or task version in its effects on information processing rates in the memory scanning task. It was concluded that PD patients do not have any cognitive slowing that is detectable with the memory scanning task.

The contribution of apraxic speech to working memory deficits in Parkinson's disease.

This article links two formerly separate areas of research associated with Parkinson's disease (PD): speech and memory. It is proposed that speech deficits occur in PD not merely at the level of muscular control, as is commonly termed dysarthria, but also at the level of speech planning and programming, more aptly described as a form of apraxia. It is further argued that PD patient groups exhibit small deficits in verbal span, and the link between apraxic speech and verbal span is elucidated via Baddeley's (1986) model of working memory. An experiment is described in which aspects of speech of 36 PD and 43 healthy control subjects were rated and classified, and measures of span and articulation rate for words of different syllable lengths were taken. Twenty-three PD subjects had dysarthric speech, while 14 of them had apraxic speech, which was associated with lower memory span scores for longer words. It is concluded that apraxic speech can be a source of reduced memory span in PD. In addition to implications for rehabilitation and therapeutic work with PD sufferers, these findings advance our theoretical understanding of the Parkinsonian syndrome.

Inhibition of return in a selective reaching task: an investigation of reference frames.

Most previous studies of inhibition of return (IOR) have examined reaction time (RT) and accuracy. These effects have been observed via saccades to targets or with key-press responses. In this study the authors examined, for the first time, IOR in components of a selective reaching task in which participants directly reached for and depressed target keys. When the interval between cue and target was 600 ms, robust IOR effects were observed in RT to begin the reach, but no effects were observed in the movement components (movement time to complete the reach and the path of the reach). However, when the cue-target interval was short (200 ms), hand paths deviated toward the cue. The results suggest that although RT measures of IOR appear to reveal perceptual rather than action-based processes, action-based representations may be briefly activated by irrelevant cues, which can be observed via analysis of three-dimensional reach path.

Effect of carbohydrates on growth of Ureaplasma urealyticum and Mycoplasma hominis.

We examined the effect of 31 carbohydrates on the growth of Ureaplasma urealyticum and Mycoplasma hominis. Arbutin and its breakdown product, hydroquinone, inhibited growth of both species; the other substrates did not alter the extent of growth. Volatile and nonvolatile end products of carbohydrate metabolism were not detected by gas chromatography.

Hand deviations away from visual cues: indirect evidence for inhibition.

Previous research has demonstrated that when a stimulus is to be ignored, the path of motion towards a target (saccade or manual reach) deviates away from the to-be-ignored stimulus. Path deviations in saccade and reaching tasks have, however, been observed in very different situations. In the saccade tasks subjects initially attended to a cue, then disengaged attention while saccading to a target. By contrast, in the selective reaching tasks attention was continuously withdrawn from the to-be-ignored stimulus, as this was irrelevant throughout the experiment. In the two experiments reported here, cues similar to those studied in saccade tasks are examined with selective reaching procedures. Experiment 1 shows that when a coloured light-emitting diode cue, upon which subjects engage and then subsequently disengage attention, is close to the responding hand, the hand deviates away from the cue. Experiment 2 confirms this cue avoidance by showing that, compared with central fixation alone, the hand veers away from a central cue. These results confirm that the path deviations observed in saccades can also be obtained in manual reaching movements. Such findings support the notion that eye and hand movements are both affected by inhibitory mechanisms of attention.

Mental health ideologies of psychiatric nurses.

Students in graduate programs of psychiatric nursing across the United States were surveyed in terms of their individual commitment to three major mental health ideologies--community mental health ideology, psychotherapetic ideology, and somatotherapeutic ideology. In contrast to earlier research, which had indicated that psychiatric nurses are ideologically neutral, it was found in the present study that as a group these 386 young psychiatric nurses were more committed to community mental health ideology than to the other two psychiatric orientations measured.

Use of glycosyltransferases to restore pertussis toxin receptor activity to asialoagalactofetuin.

Fetuin derivatives with enzymatically altered oligosaccharide units were tested for their ability to inhibit pertussis toxin-mediated agglutination of goose erythrocytes and the binding of 125I-labeled fetuin to pertussis toxin-coated polystyrene tubes. Fetuin oligosaccharides were sequentially degraded by treatment with: neuraminidase (asialofetuin) followed by beta-galactosidase (asialoagalactofetuin) and, lastly, with beta-N-acetylhexosaminidase (asialoagalacto-a[N-acetylglucosamino]fetuin). Asialofetuin retained only 19 and 53% of the inhibitory activity of native fetuin in the hemagglutination and 125I-fetuin binding assays, respectively. Asialoagalactofetuin showed no further reduction of inhibition in the hemagglutination system and, instead, resulted in partial recovery of inhibition in the 125I-fetuin-pertussis toxin binding assay. Asialoagalacto-a[N-acetylhexosamino]fetuin showed a further decrease in ability to inhibit pertussis toxin binding in both assays. The inhibitory activity of asialoagalactofetuin could be restored to that of native fetuin by adding back D-galactose with UDP-Gal:D-glucosyl-1,4-beta-galactosyltransferase, followed by the addition of terminal sialic acid residues with CMP-N-acetylneuraminic acid:beta-D-galactosyl-1,4-N-acetyl-beta-D-glucosamine-alpha-2,6-N- acetylneuraminyltransferase. The data suggested that a requirement for pertussis toxin binding to fetuin may be the presence of acetamido-containing sugar groups in the nonreducing terminal position of fetuin's oligosaccharides.

Action-based mechanisms of attention.

Actions, which have effects in the external world, must be spatiotopically represented in the brain. The brain is capable of representing space in many different forms (e.g. retinotopic-, environment-, head- or shoulder-centred), but we maintain that actions are represented in action-centred space, meaning that, at the cellular level, the direction of movement is defined by the activity of cells. In reaching, for example, object location is defined as the direction and distance between the origin of the hand and the target. Most importantly, we argue that more than one task-relevant action can be evoked at any moment in time. Therefore, highly efficient selection processes that accurately link vision and action have had to evolve. Research is reviewed which supports the notion of action-based inhibitory mechanisms that select the target from competing distractors.

Reaching affects saccade trajectories.

The pre-motor theory suggests that, when attention is oriented to a location, the motor systems that are involved in achieving current behavioural goals are activated. For example, when a task requires accurate reaching, attention to a location activates the motor circuits controlling saccades and manual reaches. These actions involve separate neural systems for the control of eye and hand, but we believe that the selection processes acting on neural population codes within these systems are similar and can affect each other. The attentional effect can be revealed in the subsequent movement. The present study shows that the path the eye takes as it saccades to a target is affected by whether a reach to the target is also produced. This effect is interpreted as the influence of a hand-centred frame used in reaching on the spatial frame of reference required for the saccade.