23 research outputs found
Ultrasensitive force and displacement detection using trapped ions
The ability to detect extremely small forces is vital for a variety of
disciplines including precision spin-resonance imaging, microscopy, and tests
of fundamental physical phenomena. Current force-detection sensitivity limits
have surpassed 1 (atto ) through coupling of micro or
nanofabricated mechanical resonators to a variety of physical systems including
single-electron transistors, superconducting microwave cavities, and individual
spins. These experiments have allowed for probing studies of a variety of
phenomena, but sensitivity requirements are ever-increasing as new regimes of
physical interactions are considered. Here we show that trapped atomic ions are
exquisitely sensitive force detectors, with a measured sensitivity more than
three orders of magnitude better than existing reports. We demonstrate
detection of forces as small as 174 (yocto ), with a
sensitivity 390 using crystals of Be
ions in a Penning trap. Our technique is based on the excitation of normal
motional modes in an ion trap by externally applied electric fields, detection
via and phase-coherent Doppler velocimetry, which allows for the discrimination
of ion motion with amplitudes on the scale of nanometers. These experimental
results and extracted force-detection sensitivities in the single-ion limit
validate proposals suggesting that trapped atomic ions are capable of detecting
of forces with sensitivity approaching 1 . We anticipate that
this demonstration will be strongly motivational for the development of a new
class of deployable trapped-ion-based sensors, and will permit scientists to
access new regimes in materials science.Comment: Expanded introduction and analysis. Methods section added. Subject to
press embarg
From PALSA PLUS to PALM PLUS: adapting and developing a South African guideline and training intervention to better integrate HIV/AIDS care with primary care in rural health centers in Malawi
<p>Abstract</p> <p>Background</p> <p>Only about one-third of eligible HIV/AIDS patients receive anti-retroviral treatment (ART). Decentralizing treatment is crucial to wider and more equitable access, but key obstacles are a shortage of trained healthcare workers (HCW) and challenges integrating HIV/AIDS care with other primary care. This report describes the development of a guideline and training program (PALM PLUS) designed to integrate HIV/AIDS care with other primary care in Malawi. PALM PLUS was adapted from PALSA PLUS, developed in South Africa, and targets middle-cadre HCWs (clinical officers, nurses, and medical assistants). We adapted it to align with Malawi's national treatment protocols, more varied healthcare workforce, and weaker health system infrastructure.</p> <p>Methods/Design</p> <p>The international research team included the developers of the PALSA PLUS program, key Malawi-based team members and personnel from national and district level Ministry of Health (MoH), professional associations, and an international non-governmental organization. The PALSA PLUS guideline was extensively revised based on Malawi national disease-specific guidelines. Advice and input was sought from local clinical experts, including middle-cadre personnel, as well as Malawi MoH personnel and representatives of Malawian professional associations.</p> <p>Results</p> <p>An integrated guideline adapted to Malawian protocols for adults with respiratory conditions, HIV/AIDS, tuberculosis, and other primary care conditions was developed. The training program was adapted to Malawi's health system and district-level supervision structure. PALM PLUS is currently being piloted in a cluster-randomized trial in health centers in Malawi (ISRCTN47805230).</p> <p>Discussion</p> <p>The PALM PLUS guideline and training intervention targets primary care middle-cadre HCWs with the objective of improving HCW satisfaction and retention, and the quality of patient care. Successful adaptations are feasible, even across health systems as different as those of South Africa and Malawi.</p
Long-term weather sensitivity of open sand grasslands of the KiskunsĂĄg Sand Ridge forest-steppe mosaic after wildfires
Characterization of behavioral, signaling and cytokine alterations in a rat neurodevelopmental model for schizophrenia, and their reversal by the 5-HTâ receptor antagonist SB-399885
Post-weaning social isolation of rats produces neuroanatomical, neurochemical and behavioral alterations resembling some core features of schizophrenia. This study examined the ability of the 5-HTâ receptor antagonist SB-399885 to reverse isolation-induced cognitive deficits, then investigated alterations in hippocampal cell proliferation and hippocampal and frontal cortical expression of selected intracellular signaling molecules and cytokines. Male Lister-hooded rats (weaned on post-natal day 21-24 and housed individually or in groups of 3-4) received six i.p. injections of vehicle (1% Tween 80, 1 mL/kg) or SB-399885 (5 or 10 mg/kg) over a two week period starting 40 days post-weaning, on the days that locomotor activity, novel object discrimination (NOD), pre-pulse inhibition of acoustic startle and acquisition, retention and extinction of a conditioned freezing response (CFR) were assessed. Tissue was collected 24 h after the final injection for immunohistochemistry, reverse-phase protein microarray and western blotting. Isolation rearing impaired NOD and cue-mediated CFR, decreased cell proliferation within the dentate gyrus, and elevated hippocampal TNFα levels and Cdc42 expression. SB-399885 reversed the NOD deficit and partially normalized CFR and cell proliferation. These effects were accompanied by altered expression of several members of the c-Jun N-terminal Kinase (JNK) and p38 MAPK signaling pathways (including TAK1, MKK4 and STAT3). Although JNK and p38 themselves were unaltered at this time point hippocampal TAK1 expression and phosphorylation correlated with visual recognition memory in the NOD task. Continued use of this neurodevelopmental model could further elucidate the neurobiology of schizophrenia and aid assessment of novel therapies for drug-resistant cognitive symptoms
Ecological effects of fire-breaks in the montane grasslands of the southern Drakensberg, South Africa
Fire-breaks, by legislation, are burnt annually before mid-winter in the
southern Drakensberg, affecting 5â10% of the landscape, and resulting in marked
selection for the early season flush by both livestock and wildlife. This study
investigated whether this severe defoliation regime has had an effect on
surface soil properties, botanical composition, plant diversity, phytomass
production, and the nutrient content of phytomass by comparing paired samples
of grassland and immediately adjacent fire-breaks. Fire-breaks differed
quantitatively in composition from adjacent grassland although both were
characterised as Themeda
triandraâTristachya leucothrix grassland. Only two grass species of lesser
abundance, Brachiaria serrata and Eragrostis racemosa, were clearly more
abundant on fire-breaks. Differences in plant diversity (species mâ2,
species 20mâ2) were slight. Surface soil of fire-breaks compared
with grasslands was slightly more acidic (0.2 units), lower in carbon (1%
difference), and lower in total nitrogen (0.03% difference), suggesting
deterioration of soil conditions on fire-breaks. Phytomass of fire-breaks and
of grasslands burnt in early spring in the season sampled (biennial or greater
burning frequency) were equivalent by February, indicating there has been no
decline in productivity over time. Concentration of nitrogen, phosphorus,
calcium, magnesium, potassium, sodium, zinc and copper in above-ground
phytomass did not differ between fire-breaks and grasslands, although
concentration of manganese tended to be greater in grassland. Expected seasonal
trends, especially for nitrogen and phosphorus, were apparent. Fire-breaks
therefore appear to be a sustainable management practice, in part because
mid-winter burning allows sufficient recovery of canopy cover to mitigate
against erosion by high intensity spring storms and the duration of grazing
impact is alleviated by spring burning elsewhere. Grazing impact on fire-breaks
may become more severe if grassland burning becomes more infrequent.
Keywords: composition, forage quality, Highland Sourveld, nutrients, ordination,
productionAfrican Journal of Range & Forage Science 2004, 21(1):
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