124 research outputs found
Inferring hydroxyl layer peak heights from ground-based measurements of OH(6-2) band integrated emission rate at Longyearbyen (78 N, 16 E)
Measurements of hydroxyl nightglow emissions
over Longyearbyen (78 N, 16 E) recorded simultaneously
by the SABER instrument onboard the TIMED satellite and
a ground-based Ebert-Fastie spectrometer have been used to
derive an empirical formula for the height of the OH layer
as a function of the integrated emission rate (IER). Altitude
profiles of the OH volume emission rate (VER) derived from
SABER observations over a period of more than six years
provided a relation between the height of the OH layer peak
and the integrated emission rate following the procedure described
by Liu and Shepherd (2006). An extended period of
overlap of SABER and ground-based spectrometer measurements
of OH(6-2) IER during the 2003â2004 winter season
allowed us to express ground-based IER values in terms of
their satellite equivalents. The combination of these two formulae
provided a method for inferring an altitude of the OH
emission layer over Longyearbyen from ground-based measurements
alone. Such a method is required when SABER
is in a southward looking yaw cycle. In the SABER data
for the period 2002â2008, the peak altitude of the OH layer
ranged from a minimum near 76 km to a maximum near
90 km. The uncertainty in the inferred altitude of the peak
emission, which includes a contribution for atmospheric extinction,
was estimated to be±2.7 km and is comparable with
the ±2.6 km value quoted for the nominal altitude (87 km)
of the OH layer. Longer periods of overlap of satellite and
ground-based measurements together with simultaneous onsite
measurements of atmospheric extinction could reduce
the uncertainty to approximately 2 km
Inferring hydroxyl layer peak heights from ground-based measurements of OH(6-2) band integrated emission rate at Longyearbyen (78 N, 16 E)
Measurements of hydroxyl nightglow emissions
over Longyearbyen (78 N, 16 E) recorded simultaneously
by the SABER instrument onboard the TIMED satellite and
a ground-based Ebert-Fastie spectrometer have been used to
derive an empirical formula for the height of the OH layer
as a function of the integrated emission rate (IER). Altitude
profiles of the OH volume emission rate (VER) derived from
SABER observations over a period of more than six years
provided a relation between the height of the OH layer peak
and the integrated emission rate following the procedure described
by Liu and Shepherd (2006). An extended period of
overlap of SABER and ground-based spectrometer measurements
of OH(6-2) IER during the 2003â2004 winter season
allowed us to express ground-based IER values in terms of
their satellite equivalents. The combination of these two formulae
provided a method for inferring an altitude of the OH
emission layer over Longyearbyen from ground-based measurements
alone. Such a method is required when SABER
is in a southward looking yaw cycle. In the SABER data
for the period 2002â2008, the peak altitude of the OH layer
ranged from a minimum near 76 km to a maximum near
90 km. The uncertainty in the inferred altitude of the peak
emission, which includes a contribution for atmospheric extinction,
was estimated to be±2.7 km and is comparable with
the ±2.6 km value quoted for the nominal altitude (87 km)
of the OH layer. Longer periods of overlap of satellite and
ground-based measurements together with simultaneous onsite
measurements of atmospheric extinction could reduce
the uncertainty to approximately 2 km
A biochemical and ultrastructural evaluation of the type 2 Gaucher mouse
Gaucher mice, created by targeted disruption of the glucocerebrosidase gene, are totally deficient in glucocerebrosidase and have a rapidly deteriorating clinical course analogous to the most severely affected type 2 human patients. An ultrastructural study of tissues from these mice revealed glucocerebroside accumulation in bone marrow, liver, spleen, and brain. This glycolipid had a characteristic elongated tubular structure and was contained in lysosomes, as demonstrated by colocalization with both ingested carbon particles and cathepsin D. In the central nervous system (CNS), glucocerebroside was diffusely stored in microglia cells and in brainstem and spinal cord neurons, but not in neurons of the cerebellum or cerebral cortex. This rostralcaudal pattern of neuronal lipid storage in these Gaucher mice replicates the pattern seen in type 2 human Gaucher patients and clearly demonstrates that glycosphingolipid catabolism and/or accumulation varies within different brain regions. Surprisingly, the cellular pathology of tissue from these Gaucher mice was relatively mild, and suggests that the early and rapid demise of both Gaucher mice and severely affected type 2 human neonates may be the result of both a neurotoxic metabolite, such as glucosylsphingosine, and other factors, such as skin water barrier dysfunction secondary to the absence of glucocerebrosidase activity
Geochemical and physical sources of radon variation in a subterranean estuary â implications for groundwater radon activities in submarine groundwater discharge studies
Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 110 (2008): 120-127, doi:10.1016/j.marchem.2008.02.011.Submarine groundwater discharge (SGD), in form of springs and diffuse seepage,
has long been recognized as a source of chemical constituents to the coastal ocean.
Because groundwater is two to four orders of magnitude richer in radon than surface
water, it has been used as both a qualitative and a quantitative tracer of groundwater
discharge. Besides this large activity gradient, the other perceived advantage of radon
stems from its classification as noble gas; that is, its chemical behavior is expected not to
be influenced by salinity, redox, and diagenetic conditions present in aquatic
environments.
During our three-year monthly sampling of the subterranean estuary (STE) in
Waquoit Bay, MA, we found highly variable radon activities (50-1600 dpm L-1) across
the fresh-saline interface of the aquifer. We monitored pore water chemistry and radon
activity at 8 fixed depths spanning from 2 to 5.6 m across the STE, and found seasonal
fluctuations in activity at depths where elevated radon was observed. We postulate that
most of pore water 222Rn is produced from particle-surface bound 226Ra, and that the
accumulation of this radium is likely regulated by the presence of manganese
(hydr)oxides. Layers of manganese (hydr)oxides form at the salinity transition zone
(STZ), where water with high salinity, high manganese, and low redox potential mixes
with fresh water. Responding to the seasonality of aquifer recharge, the location of the
STZ and the layers with radium enriched manganese (hydr)oxide follows the seasonal
land- or bay-ward movement of the freshwater lens. This results in seasonal changes in
the depth where elevated radon activities are observed.
The conclusion of our study is that the freshwater part of the STE has a radon
signature that is completely different from the STZ or recirculated sea water. Therefore,
the radon activity in SGD will depend on the ratio of fresh and recirculated seawater in
the discharging groundwater.This work is a
result of research sponsored by NSF (OCE- 0425061 to M.A.C.) and the WHOI
Postdoctoral Scholar program (to H.D.)
Salerno's model of DNA reanalysed: could solitons have biological significance?
We investigate the sequence-dependent behaviour of localised excitations in a
toy, nonlinear model of DNA base-pair opening originally proposed by Salerno.
Specifically we ask whether ``breather'' solitons could play a role in the
facilitated location of promoters by RNA polymerase. In an effective potential
formalism, we find excellent correlation between potential minima and {\em
Escherichia coli} promoter recognition sites in the T7 bacteriophage genome.
Evidence for a similar relationship between phage promoters and downstream
coding regions is found and alternative reasons for links between AT richness
and transcriptionally-significant sites are discussed. Consideration of the
soliton energy of translocation provides a novel dynamical picture of sliding:
steep potential gradients correspond to deterministic motion, while ``flat''
regions, corresponding to homogeneous AT or GC content, are governed by random,
thermal motion. Finally we demonstrate an interesting equivalence between
planar, breather solitons and the helical motion of a sliding protein
``particle'' about a bent DNA axis.Comment: Latex file 20 pages, 5 figures. Manuscript of paper to appear in J.
Biol. Phys., accepted 02/09/0
Characterization of a Legionella pneumophila gene encoding a lipoprotein antigen
A prominent 19kDa surface antigen of Legionella pneumophila , cloned in Escherichia coli , was found to be intimately associated with peptidoglycan. The DNA region encoding this antigen was mapped on an 11.9kb plasmid by means of deletion analysis and transposon mutagenesis. PhoA + gene fusions, generated by Tn phoA insertions into this region, confirmed the presence of a gene encoding a secreted protein. PhoA + transposon insertions were also associated with loss of the 19 kDa antigen in immunoassay s using a monoclonal antibody (mAb1E9) and the replacement of the 19kDa antigen with larger fusion proteins in immunoblots using Legionella immune serum. A 1540bp PstI fragment carrying the gene was sequenced, and the open reading frame encoding the antigen was identified. The gene encodes a polypeptide 176 amino acid residues long and 18913Da in size. The presence of a signal sequence of 22 amino acids with a consensus sequence for cleavage by signal peptidase II indicates that the antigen is a lipoprotein, and striking similarity with peptidoglycan-associated lipoproteins (PALs) from E. coli (51% amino acid homology) and Haemophilus influenzae (55% homology) is noted. We conclude that the 19kDa antigen of L. pneumophila is the structural equivalent of the PAL found in other Gram-negative species and suggest that its post-translational acylation may explain its potency as an immunogen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75712/1/j.1365-2958.1991.tb00824.x.pd
Mentoring student nurses and the educational use of self: A hermeneutic phenomenological study
Background
In the United Kingdom, pre-registration nurse education relies on workplace mentors to support and assess practice learning. Despite research to clarify expectations and develop support structures, mentors nevertheless report being overwhelmed by the responsibility of mentoring alongside their clinical work. Understanding of their lived experience appears limited.
Objectives
The aim of the study was to achieve a deeper understanding of the lived experience of mentoring, searching for insights into how mentors can be better prepared and supported.
Design
The mentor lifeworld was explored utilizing a hermeneutic phenomenological methodology drawing on Heidegger.
Settings and Participants
Twelve mentors, who worked in a range of clinical settings in England were recruited via purposive and snowball sampling.
Method
Participants described their experiences of mentoring through in-depth interviews and event diaries which included ârich picturesâ. Analysis involved the application of four lifeworld existentials proposed by van Manen â temporality, spatiality, corporeality and relationality.
Findings
The essence of being a mentor was âthe educational use of selfâ. Temporality featured in the past self and moving with daily/work rhythms. Spatiality evoked issues of proximity and accountability and the inner and outer spaces of patients' bodies. Mentor corporeality revealed using the body for teaching, and mentors revealed their relationality in providing a âgood educational experienceâ and sustaining their âeducational selvesâ.
Conclusions
âThe educational use of selfâ offers insight into the lived experience of mentors, and exposes the potentially hidden elements of mentoring experience, which can inform mentor preparation and support
PHIP - a novel candidate breast cancer susceptibility locus on 6q14.1
Most non-BRCA1/2 breast cancer families have no identified genetic cause. We used linkage and haplotype analyses in familial and sporadic breast cancer cases to identify a susceptibility locus on chromosome 6q. Two independent genome-wide linkage analysis studies suggested a 3 Mb locus on chromosome 6q and two unrelated Swedish families with a LOD > 2 together seemed to share a haplotype in 6q14.1. We hypothesized that this region harbored a rare high-risk founder allele contributing to breast cancer in these two families. Sequencing of DNA and RNA from the two families did not detect any pathogenic mutations. Finally, 29 SNPs in the region were analyzed in 44,214 cases and 43,532 controls from BCAC, and the original haplotypes in the two families were suggested as low-risk alleles for European and Swedish women specifically. There was also some support for one additional independent moderate-risk allele in Swedish familial samples. The results were consistent with our previous findings in familial breast cancer and supported a breast cancer susceptibility locus at 6q14.1 around the PHIP gene.Peer reviewe
Associations of common breast cancer susceptibility alleles with risk of breast cancer subtypes in BRCA1 and BRCA2 mutation carriers
Introduction: More than 70 common alleles are known to be involved in breast cancer (BC) susceptibility, and several exhibit significant heterogeneity in their associations with different BC subtypes. Although there are differences in the association patterns between BRCA1 and BRCA2 mutation carriers and the general population for several loci, no study has comprehensively evaluated the associations of all known BC susceptibility alleles with risk of BC subtypes in BRCA1 and BRCA2 carriers. Methods: We used data from 15,252 BRCA1 and 8,211 BRCA2 carriers to analyze the associations between approximately 200,000 genetic variants on the iCOGS array and risk of BC subtypes defined by estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and triple-negative- (TN) status; morphologic subtypes; histological grade; and nodal involvement. Results: The estimated BC hazard ratios (HRs) for the 74 known BC alleles in BRCA1 carriers exhibited moderate correlations with the corresponding odds ratios from the general population. However, their associations with ER-positive BC in BRCA1 carriers were more consistent with the ER-positive as
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