bluuebunny/crossref_metadata_2025 huggingface dataset:
Ceramide Mediates Vascular Dysfunction in Diet-Induced Obesity by PP2A-Mediated Dephosphorylation of the eNOS-Akt Complex
Authors: Zhang Quan-Jiang , Holland William L. , Wilson Lloyd , Tanner Jason M. , Kearns Devin , Cahoon Judd M. , Pettey Dix , Losee Jason , Duncan Bradlee , Gale Derrick , Kowalski Christopher A. , Deeter Nicholas , Nichols Alexandrea , Deesing Michole , Arrant Colton , Ruan Ting , Boehme Christoph , McCamey Dane R. , Rou Janvida , Ambal Kapil , Narra Krishna K. , Summers Scott A. , Abel E. Dale , Symons J. David
Published: May 2012

Vascular dysfunction that accompanies obesity and insulin resistance may be mediated by lipid metabolites. We sought to determine if vascular ceramide leads to arterial dysfunction and to elucidate the underlying mechanisms. Pharmacological inhibition of de novo ceramide synthesis, using the Ser palmitoyl transferase inhibitor myriocin, and heterozygous deletion of dihydroceramide desaturase prevented vascular dysfunction and hypertension in mice after high-fat feeding. These findings were recapitulated in isolated arteries in vitro, confirming that ceramide impairs endothelium-dependent vasorelaxation in a tissue-autonomous manner. Studies in endothelial cells reveal that de novo ceramide biosynthesis induced protein phosphatase 2A (PP2A) association directly with the endothelial nitric oxide synthase (eNOS)/Akt/Hsp90 complex that was concurrent with decreased basal and agonist-stimulated eNOS phosphorylation. PP2A attenuates eNOS phosphorylation by preventing phosphorylation of the pool of Akt that colocalizes with eNOS and by dephosphorylating eNOS. Ceramide decreased the association between PP2A and the predominantly cytosolic inhibitor 2 of PP2A. We conclude that ceramide mediates obesity-related vascular dysfunction by a mechanism that involves PP2A-mediated disruption of the eNOS/Akt/Hsp90 signaling complex. These results provide important insight into a pathway that represents a novel target for reversing obesity-related vascular dysfunction.
Grading New York
Authors: Winters Marcus A. , Cowen Joshua M.
Published: May 2012

This article uses a regression discontinuity approach to study the influence of New York City’s school grading policy on student math and English language arts (ELA) achievement. We find evidence that students in schools receiving a failing grade realized positive effects in English in the 1st year of sanction, but we find no statistically significant effect during the 1st year of sanction on student math achievement. There is no evidence that receiving letter grades other than F had positive effects. Finally, we show that students in schools that received an F-grade in the 1st year continued to realize a positive average ELA effect in the 2nd year and that a positive math effect was evident as well.
Antibody-Based Immunotoxins for the Treatment of Cancer
Authors: Becker Nurit , Benhar Itai
Published: May 2012

Antibody-based immunotoxins comprise an important group in targeted cancer therapeutics. These chimeric proteins are a form of biological guided missiles that combine a targeting moiety with a potent effector molecule. The targeting moiety is mostly a monoclonal antibody (MAb) or a recombinant antibody-based fragment that confers target specificity to the immunotoxin. The effector domain is a potent protein toxin of bacterial or plant origin, which, following binding to the target cells, undergoes internalization and causes cell death. Over time and following research progression, immunotoxins become better fitted to their purpose, losing immunogenic fragments and non-specific targeting moieties. Many immunotoxins have gone through clinical evaluation. Some of these have been shown to be active and work is progressing with them in the form of further clinical trials. Others, mostly developed in the previous century, failed to generate a response in patients, or even caused undesired side effects. This article reviews the antibody and protein-toxin based immunotoxins that were clinically evaluated up to the present day.
Relationships Between Base-Catalyzed Hydrolysis Rates or Glutathione Reactivity for Acrylates and Methacrylates and Their NMR Spectra or Heat of Formation
Authors: Fujisawa Seiichiro , Kadoma Yoshinori
Published: May 2012

The NMR chemical shift, i.e., the π-electron density of the double bond, of acrylates and methacrylates is related to the reactivity of their monomers. We investigated quantitative structure-property relationships (QSPRs) between the base-catalyzed hydrolysis rate constants (k1) or the rate constant with glutathione (GSH) (log kGSH) for acrylates and methacrylates and the 13C NMR chemical shifts of their α,β-unsaturated carbonyl groups (δCα and δCβ) or heat of formation (Hf) calculated by the semi-empirical MO method. Reported data for the independent variables were employed. A significant linear relationship between k1 and δCβ, but not δCα, was obtained for methacrylates (r2 = 0.93), but not for acrylates. Also, a significant relationship between k1 and Hf was obtained for both acrylates and methacrylates (r2 = 0.89). By contrast, log kGSH for acrylates and methacrylates was linearly related to their δCβ (r2 = 0.99), but not to Hf. These findings indicate that the 13C NMR chemical shifts and calculated Hf values for acrylates and methacrylates could be valuable for estimating the hydrolysis rate constants and GSH reactivity of these compounds. Also, these data for monomers may be an important tool for examining mechanisms of reactivity.
Biochemical Traits, Survival and Biological Properties of the Probiotic Lactobacillus plantarum Grown in the Presence of Prebiotic Inulin and Pectin as Energy Source
Authors: Nazzaro Filomena , Fratianni Florinda , Orlando Pierangelo , Coppola Raffaele
Published: May 2012

The viability of the probiotic strain Lactobacillus plantarum subsp. plantarum, after its passage through simulated gastric and pancreatic juices, was evaluated as function of its pre-growth in a medium containing the known prebiotics pectin or inulin, and was compared to glucose used as control. The presence of pectin or inulin did not markedly affect the growth (10.07 log10 colony forming units/mL and 10.28 log10 colony forming units/mL for pectin and inulin respectively versus 10.42 log10 colony forming units/mL obtained for glucose). Pectin and inulin, in contrast to glucose, induced cell stress resistance against gastrointestinal juices (D log101.5 and 2.4 colony forming units/mL respectively, versus D log10 4.0 for glucose). The data were corroborated by the analysis of the protein pattern following stress treatments which, in the case of microbial cells grown with glucose, revealed a more marked protein degradation after the double passage through simulated gastric and intestinal juices. Inulin stimulated the production of the relevant healthy bio-molecule butyrate, which amount was 30% higher respect of growth in the presence of glucose. Inulin and pectin improved cell DPPH scavenging activity, and an impressive hydrophobicity (35.28% and 34.81%, respectively) was observed with respect to the microbial growth in presence of glucose (3.39%).
Pharmacists and Harm Reduction: A Review of Current Practices and Attitudes
Authors: Watson Tyler , Hughes Christine
Published: May 2012

Background:

Injection drug use and other high-risk behaviours are the cause of signifcant morbidity and mortality and thus have been the focus of many health promotion strategies. Community pharmacists are considered underutilized health providers and are often thought to be more accessible than other health professionals. The purpose of this review is to provide an overview of community pharma cists' practices as well as pharmacists' attitudes and identified barriers toward providing harm reduction services. We will highlight the major harm reduction services being offered through community pharmacies, as well as identify barriers to implementing these services.

Methods:

A review of the literature from 1995 to 2011 was conducted using the electronic databases MEDLINE, PubMed and Scopus, encompassing pharmacists' involvement in harm reduction services. Keywords included pharmacist, harm reduction, disease prevention, health promotion, attitudes, competence and barriers. References of included articles were examined to identify further relevant literature.

Results:

Pharmacists are primarily involved in providing clean needles to injection drug users, as well as opioid substitution. Pharmacists generally have a positive attitude toward providing health promotion and harm reduction programs and express some interest in increasing their role in this area. Common barriers to expanding harm reduction strategies in community pharmacists' practice include lack of time and training, insufficient remuneration, fear of attracting unruly clientele and inadequate communication between health providers.

Conclusion:

As one of the most accessible health care providers, community pharmacists are in an ideal position to provide meaningful services to injection drug users. However, in order to do so, pharmacists require additional support in the form of better health team and system integration, as well as remuneration models.
Head Office Commitment to Quality-Related Event Reporting in Community Pharmacy
Authors: Scobie Andrea C. , Boyle Todd A. , MacKinnon Neil J. , Mahaffey Thomas
Published: May 2012

Background:

This research explores how perceptions of head office commitment to quality-related event (QRE) reporting differ between pharmacy staff type and between pharmacies with high and low QRE reporting and learning performance. QREs include known, alleged or suspected medication errors that reach the patient as well as medication errors that are intercepted prior to dispensing.

Methods:

A survey questionnaire was mailed in the spring of 2010 to 427 pharmacy managers, pharmacists and pharmacy technicians in Nova Scotia. Nonparametric statistics were used to determine differences based on pharmacy staff type and pharmacy performance. Content analysis was used to analyze the responses to open-ended survey questions.

Results:

A total of 210 surveys were returned, for a response rate of 49.2%. However, the current study used only the subgroup of pharmacy staff who self-reported working at a chain pharmacy, for a total of 124 usable questionnaires. The results showed that community pharmacies viewed head office commitment to QRE reporting as an area to improve. In general, high-performing pharmacies ranked head office commitment higher than low-performing pharmacies.

Discussion:

One possible reason why high-performing pharmacies ranked the variables higher may be that increased levels of head office support for QRE processes have led these pharmacies to adopt and commit to QRE processes and thus increase their performance.

Conclusion:

Demonstrated commitment to QRE reporting, ongoing encouragement and targeted messages to staff could be important steps for head office to increase QRE reporting and learning in community pharmacies.
Credentialing: Understanding the Terms
Authors: Dickerson Pamela S.
Published: May 2012

Credentialing is an umbrella term that encompasses several categories, many of which have an impact when considering professional development for registered nurses. This column identifies select categories within the credentialing domain.
Analysis of Initial Injury Radiographs of Occult Femoral Neck Fractures in Elderly Patients: A Pilot Study
Authors: Chiang Chao-Ching , Wu Hung-Ta , Lin Chien-Fu Jeff , Tzeng Yun-Hsuan , Huang Ching-Kuei , Chen Wei-Ming , Liu Chien-Lin
Published: May 2012

Diagnosis of occult hip fractures by initial radiographs remains challenging in the emergency department. Previously, the gold standard for accurate diagnosis of occult hip fractures was magnetic resonance imaging. This study used initial radiographs obtained in the emergency department to evaluate specific signs and measurements as diagnostic references for occult femoral neck fractures in elderly patients.

Initial negative radiographs were reviewed for 2 groups of patients: a group with occult femoral neck fractures (n=16) and a group without fractures (n=32). Reviews of initial radiographs and all imaging studies were performed by a senior orthopedist (C-C.C.) and a radiologist (H-T.W.). Diagnostic signs included lateral, medial, anterior, and posterior signs; measurements included elevation of the fat pad and external rotation of the femur. The prevalence of occult femoral neck fracture was 3.3%. Initial radiographs of occult femoral neck fractures were not routinely negative; 14 (87.5%) of 16 patients with fractures had at least 1 radiographic sign. Using the positive lateral or posterior sign as the diagnostic reference, the sensitivity was 0.875 and the specificity was 0.906. When elevation of the fat pad was ⩾1.5 mm, the sensitivity was 0.867 and the specificity was 0.857 for the diagnosis of occult femoral neck fracture.

The lateral and posterior signs and elevation of the fat pad ⩾1.5 mm on initial radiographs are recommended as diagnostic references for occult femoral neck fracture. These references are clearly defined and may offer important information for all clinicians and radiologists in the emergency department.
Fly Fishing–related Lesser Tuberosity Avulsion in an Adolescent
Authors: Teixeira Rafael P. , Johnson Alan R. , Higgins Brendan T. , Carrino John A. , McFarland Edward G.
Published: May 2012

Stress lesions of the shoulder in athletic and active adolescents are most commonly associated with overhead sports. One of the most uncommon stress lesions of the shoulder in adolescents is an avulsion of the lesser tuberosity of the proximal humerus. To our knowledge, only 2 other cases of lesser tuberosity avulsions from repetitive motion have been reported, both of which were secondary to baseball pitching.

This article describes a case of an isolated partial avulsion of the lesser tuberosity of the humerus in an adolescent as a result of repetitive stress from fly fishing. The patient had no symptoms in his shoulder until after casting for approximately 10 hours a day for 3 days. He presented with anterior shoulder pain that worsened with abduction and external rotation. On examination, he had tenderness over the lesser tuberosity and pain with subscapularis muscle testing, such as the lift-off test. He had a negative apprehension sign but no signs of a superior labrum tear. Conventional radiography with an axillary view confirmed the diagnosis. He recovered with rest and gradual return to activities. Two years after injury, the patient had no limitations functionally, and his shoulder examination was normal.

This case highlights the importance of being aware that (1) this lesion can occur in activities other than baseball, (2) characteristic physical findings exist with this lesion, (3) obtaining an axillary radiograph can confirm diagnosis, and (4) these avulsions can be treated successfully with nonoperative interventions.
Factors Associated With Strabismus in Spina Bifida Myelomeningocele
Authors: Anderson Heather A. , Stuebing Karla K. , Buncic Ray , Mazow Malcolm , Fletcher Jack M.
Published: May 2012

Purpose:

Higher prevalence of strabismus in individuals with spina bifida myelomeningocele (SBM) has previously been attributed to hydrocephalus; however, SBM is associated with many other complications. This study investigates the relation between strabismus and other factors in SBM.

Methods:

Children aged 3 to 18 years with SBM (n = 112) received an eye examination including assessment of ocular alignment by cover or Hirschberg test. Gestational age, respiratory distress at birth, birth weight, maternal age at birth, number of shunt revisions, and spinal lesion level were also obtained. The relation between these factors and strabismus was analyzed.

Results:

Forty-two participants had strabismus. Maternal age (
P
= .4) and respiratory distress (
P
= .6) were not significantly related to strabismus. Lower birth weight was suggestive of a relation with strabismus (logistic regression,
P
= .05) and younger gestational age was related to strabismus (logistic regression,
P
= .01). Participants who had at least one shunt revision were more likely to have strabismus (Fisher’s exact test,
P
= .038). Spinal lesion level was significantly related to strabismus with increased likelihood of strabismus for spinal lesions closer to the brain (Wald chi-square, 1,100 = 4.29,
P
= .038).

Conclusion:

These findings indicate that several factors are associated with strabismus in SBM. Some of these factors (lower birth weight and younger gestational age) are associated with strabismus in the general population, whereas the association of strabismus and level of spinal lesion may be unique to SBM and may be related to the more severe brain dysmorphology associated with upper level spinal lesions.
Comparison of Preoperative and Postoperative Anterior Segment Measurements With Pentacam
®
in Strabismus Surgery
Authors: Jung Jae Ho , Choi Hee Young
Published: May 2012

Purpose:

This study was intended to evaluate the effect of horizontal muscle surgery on anterior segment measurements in patients with strabismus.

Methods:

Forty-two eyes of 28 patients with exotropia undergoing recession or recession combined with resection procedure were included. Consecutive cases were imaged using a Pentacam (Oculus, Inc., Berlin, Germany) immediately prior to surgery and 1 and 3 months after surgery. The refractive power of the anterior surface of the cornea on the horizontal and vertical axis, the thinnest corneal thickness, anterior chamber depth, anterior chamber volume, and cornea volume were analyzed. The clinical characteristics of patients, visual acuity, astigmatism, and size of the deviations before and after surgery were reviewed.

Results:

Muscle recession and recession plus resection surgery were performed in 28 and 14 eyes, respectively. Overall, no significant changes were noted when comparing preoperative and postoperative data. Patients were divided into two groups, recession or recession plus resection, and only anterior chamber depth was found to be significantly reduced in the recession group 1 month postoperatively. Three months postoperatively, the reduced anterior chamber depth in the recession group returned to the preoperative value.

Conclusion:

In this series, the recession procedure in patients with strabismus induced an anterior chamber depth change during the early postoperative period. However, the anterior chamber depth returned to its preoperative state by 3 months after surgery. These findings indicate that extraocular muscle surgery could induce reversible changes to the anterior segment of the eye.
Foldable Iris-fixated Phakic Intraocular Lens vs Femtosecond Laser–assisted LASIK for Myopia Between −6.00 and −9.00 Diopters
Authors: Albarrán-Diego César , Muñoz Gonzalo , Ferrer-Blasco Teresa , García-Lázaro Santiago , Belda-Salmerón Lurdes
Published: May 2012

PURPOSE:

To compare visual, refractive, and clinical outcomes of foldable iris-fixated phakic intraocular lens (PIOL) implantation versus femtosecond laser–assisted LASIK for myopia between −6.00 and −9.00 diopters (D).

METHODS:

Forty-six myopic patients were randomized to undergo bilateral Artiflex (Ophtec BV) PIOL implantation or bilateral femtosecond laser–assisted conventional LASIK with the VISX S2 (Abbott Medical Optics). Refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuity, contrast sensitivity, corneal endothelial cell count, rate of retreatment, and complications were compared.

RESULTS:

Twelve months after surgery, no statistically significant differences were noted in spherical equivalent refraction (
P
=.19) or UDVA (
P
=.28), whereas CDVA was better in the PIOL group (
P
<.001). Spherical equivalent refraction was within ±0.50 D in 42 (91.3%) LASIK eyes and 41 (89.1%) PIOL eyes (
P
>.99). The percentage of eyes gaining lines of CDVA was significantly higher in the PIOL group (50.0% vs 8.7%;
P
<.001). Contrast sensitivity was better for PIOL eyes at 1.5 cycles per degree (cpd) (
P
=.03) and 6 cpd (
P
=.008). The LASIK eyes showed a mean endothelial cell count increase of 3.7%±2.8%, whereas PIOL eyes showed a mean decrease of 9.1%±2.0% (
P
<.001). The rate of retreatment was similar (
P
=.37), and no serious complications occurred in either group.

CONCLUSIONS:

The Artiflex PIOL provided better CDVA and contrast sensitivity at high spatial frequencies than femtosecond laser–assisted conventional LASIK, suggesting that PIOL implantation is a reasonable option for myopia between −6.00 and −9.00 D.
SD-OCT in Pigmented Paravenous Retinochoroidal Atrophy
Authors: Ghosh Basudeb , Goel Neha , Batta Supriya , Raina Usha Kaul
Published: May 2012

Pigmented paravenous retinochoroidal atrophy (PPRCA) is a rare disease characterized by bilateral retinochoroidal atrophy and pigmentation along the retinal veins. The authors describe spectral-domain optical coherence tomography (SD-OCT) in a case of PPRCA. The right macula showed a lamellar macular hole. In addition, scans were taken through the affected areas along the retinal veins that revealed the location of the pigment and other features. These findings have not been reported previously.
Differential Regulation of the Let-7 Family of MicroRNAs in CD4+ T Cells Alters IL-10 Expression
Authors: Swaminathan Sanjay , Suzuki Kazuo , Seddiki Nabila , Kaplan Warren , Cowley Mark J. , Hood Chantelle L. , Clancy Jennifer L. , Murray Daniel D. , Méndez Catalina , Gelgor Linda , Anderson Ben , Roth Norman , Cooper David A. , Kelleher Anthony D.
Published: May 2012

MicroRNAs (miRNAs) are ∼22-nt small RNAs that are important regulators of mRNA turnover and translation. Recent studies have shown the importance of the miRNA pathway in HIV-1 infection, particularly in maintaining latency. Our initial in vitro studies demonstrated that HIV-1–infected HUT78 cells expressed significantly higher IL-10 levels compared with uninfected cultures. IL-10 plays an important role in the dysregulated cytotoxic T cell response to HIV-1, and in silico algorithms suggested that let-7 miRNAs target IL10 mRNA. In a time course experiment, we demonstrated that let-7 miRNAs fall rapidly following HIV-1 infection in HUT78 cells with concomitant rises in IL-10. To show a direct link between let-7 and IL-10, forced overexpression of let-7 miRNAs resulted in significantly reduced IL-10 levels, whereas inhibition of the function of these miRNAs increased IL-10. To demonstrate the relevance of these results, we focused our attention on CD4+ T cells from uninfected healthy controls, chronic HIV-1–infected patients, and long-term nonprogressors. We characterized miRNA changes in CD4+ T cells from these three groups and demonstrated that let-7 miRNAs were highly expressed in CD4+ T cells from healthy controls and let-7 miRNAs were significantly decreased in chronic HIV-1 infected compared with both healthy controls and long-term nonprogressors. We describe a novel mechanism whereby IL-10 levels can be potentially modulated by changes to let-7 miRNAs. In HIV-1 infection, the decrease in let-7 miRNAs may result in an increase in IL-10 from CD4+ T cells and provide the virus with an important survival advantage by manipulating the host immune response.
Protein Kinase C-θ Promotes Th17 Differentiation via Upregulation of Stat3
Authors: Kwon Myung-Ja , Ma Jian , Ding Yan , Wang Ruiqing , Sun Zuoming
Published: May 2012

Although protein kinase C-θ (PKC-θ)-deficient mice are resistant to the induction of Th17-dependent experimental autoimmune encephalomyelitis, the function of PKC-θ in Th17 differentiation remains unknown. In this article, we show that purified, naive CD4 PKC-θ−/− T cells were defective in Th17 differentiation, whereas Th1 and Th2 differentiation appeared normal. Activation of PKC-θ with PMA promoted Th17 differentiation in wild type (WT) but not PKC-θ−/− T cells. Furthermore, PKC-θ−/− T cells had notably lower levels of Stat3, a transcription factor required for Th17 differentiation, and PMA markedly stimulated the expression of Stat3 in WT but not PKC-θ−/− T cells. In contrast, activation of Stat4 and Stat6, which are critical for Th1 and Th2 differentiation, was normal in PKC-θ−/− T cells. Forced expression of Stat3 significantly increased Th17 differentiation in PKC-θ−/− T cells, suggesting that reduced Stat3 levels were responsible for impaired Th17 differentiation, and that Stat3 lies downstream of PKC-θ. Constitutively active PKC-θ, or WT PKC-θ activated by either PMA or TCR cross-linking, stimulated expression of a luciferase reporter gene driven by the Stat3 promoter. PKC-θ–mediated activation of the Stat3 promoter was inhibited by dominant-negative AP-1 and IκB kinase-β, but stimulated by WT AP-1 and IκB kinase-β, suggesting that PKC-θ stimulates Stat3 transcription via the AP-1 and NF-κB pathways. Lastly, conditions favoring Th17 differentiation induced the highest activation level of PKC-θ. Altogether, the data indicate that PKC-θ integrates the signals from TCR signaling and Th17 priming cytokines to upregulate Stat3 via NF-κB and AP-1, resulting in the stimulation of Th17 differentiation.
Aminopeptidase Substrate Preference Affects HIV Epitope Presentation and Predicts Immune Escape Patterns in HIV-Infected Individuals
Authors: Zhang Shao Chong , Martin Eric , Shimada Mariko , Godfrey Sasha Blue , Fricke Jennifer , Locastro Shirley , Lai Nicole Y. , Liebesny Paul , Carlson Jonathan M. , Brumme Chanson J. , Ogbechie Oluwatobi Awele , Chen Huabiao , Walker Bruce D. , Brumme Zabrina L. , Kavanagh Daniel G. , Le Gall Sylvie
Published: May 2012

Viruses evade immune detection partly through immune-associated mutations. Analyses of HIV sequences derived from infected individuals have identified numerous examples of HLA-associated mutations within or adjacent to T cell epitopes, but the potential impact of most mutations on epitope production and presentation remains unclear. The multistep breakdown of proteins into epitopes includes trimming of N-extended peptides into epitopes by aminopeptidases before loading onto MHC class I molecules. Definition of sequence signatures that modulate epitope production would lead to a better understanding of factors driving viral evolution and immune escape at the population level. In this study, we identified cytosolic aminopeptidases cleavage preferences in primary cells and its impact on HIV Ag degradation into epitopes in primary human cell extracts by mass spectrometry and on epitope presentation to CTL. We observed a hierarchy of preferred amino acid cleavage by cytosolic aminopeptidases. We demonstrated that flanking mutations producing more or less cleavable motifs can increase or decrease epitope production and presentation by up to 14-fold. We found that the efficiency of epitope production correlates with cleavability of flanking residues. These in vitro findings were supported by in vivo population-level analyses of clinically derived viral sequences from 1134 antiretroviral-naive HIV-infected individuals: HLA-associated mutations immune pressures drove the selection of residues that are less cleavable by aminopeptidases predominantly at N-flanking sites, leading to reduced epitope production and immune recognition. These results underscore an important and widespread role of Ag processing mutations in HIV immune escape and identify molecular mechanisms underlying impaired epitope presentation.
Production of individual marine organic aggregates using Paramagnetic Microspheres: A new tool for examining microbial associations with aggregates
Authors: Mari Xavier , Rochelle‐Newall Emma , Torréton Jean‐Pascal , Pringault Olivier , Bettarel Yvan , Motegi Chiaki , Weinbauer Markus G.
Published: May 2012

We describe a new method to produce marine aggregates from natural organic material based on the sticking properties of transparent exopolymeric particles. Seawater samples were prescreened and ultrafiltered to concentrate the 30 kDa to 10 µm size fraction. First, we produced small magnetizable aggregates by combining glass microfibers and paramagnetic 1‐µm beads with the organic matter present in the concentrated solution. The second step involved clustering the small aggregates into a single macro‐aggregate, using a small ringshaped magnet as an aggregation nucleus. Viral and bacterial densities, determined after dissolution of the newly formed aggregates with methanol, averaged 13.8 × 106 ± 3.6 × 106 vir. agg.−1 and 4.1 × 106 ± 1.1 × 106 bact. agg.−1. Bacterial respiration and production measurements of single aggregates averaged 8.47 ± 1.72 nmol O2 agg.−1 h−1 and 1.54 ± 0.45 ng C agg.−1 h−1, respectively. Particulate organic carbon and nitrogen content of the newly formed macro‐aggregates averaged 31.92 ± 2.67 µg C agg.−1 and 3.44 ± 0.43 µg N agg.−1, respectively. This approach allows the concentration and isolation of the organic matter precursors that compose natural aggregates and provides a simple protocol for recombining those precursors into single newly formed macro‐aggregates, which can then be easily manipulated for further investigation. This method is a new tool for investigations into the interactions between microorganisms and marine aggregates and their implications at the ecosystem level, but also into the interactions between aggregates and dissolved organic or inorganic substances.
GEOTRACES intercalibration of 230Th, 232Th, 231Pa, and prospects for 10Be
Authors: Anderson Robert F. , Fleisher Martin Q. , Robinson Laura F. , Edwards R. Lawrence , Hoff John A. , Moran S. Bradley , van der Loeff Michiel Rutgers , Thomas Alexander L. , Roy‐Barman Matthieu , Francois Roger
Published: May 2012

Nineteen labs representing nine nations participated in the GEOTRACES intercalibration initiative that determined concentrations of 232Th, 230Th, 231Pa, or 10Be in seawater, suspended particles or sediments. Results generally demonstrated good agreement among labs that analyzed marine sediments. Two sets of seawater samples, aliquots of particulate material filtered in situ, and/or aliquots of biogenic sediments were distributed to participating labs. Internal consistency among participating labs improved substantially between the first and second set of seawater samples. Contamination was a serious problem for 232Th. Standard Niskin bottles introduced no detectable contamination, whereas sample containers, reagents, and labware were implicated as sources of contamination. No detectable differences in concentrations of dissolved 232Th, 230Th, or 231Pa were observed among samples of seawater filtered through Nuclepore, Supor, or QMA (quartz) filters with pore diameters ranging between 0.4 and 1.0 µm. Isotope yield monitors equilibrate with dissolved Th in seawater on a time scale of much less than 1 day. Samples of filtered seawater acidified to a pH between 1.7 and 1.8 experienced no detectable loss of dissolved Th or Pa during storage for up to 3 years. The Bermuda Atlantic Time Series station will serve as a GEOTRACES baseline station for future intercalibration of 232Th and 230Th concentrations in seawater. Efforts to improve blanks and standard calibration are ongoing, as is the development of methods to determine concentrations of particulate nuclides, tests of different filtration methods, and an increasing awareness of the need to define protocols for reporting uncertainties.
Pre‐column liquid chromatographic determination of dipicolinic acid from bacterial endospores
Authors: Lomstein Bente Aa. , Jørgensen Bo Barker
Published: May 2012

A high performance liquid chromatographic (HPLC) method for fluorescence detection of dipicolinic acid (DPA), a unique component of bacterial endospores, was developed for rapid and highly sensitive quantification of endospores. DPA was pre‐column complexed to the lanthanide metal terbium (Tb3+). Surplus free Tb3+ and the Tb3+‐DPA complex were separated by reverse‐phase gradient chromatography and the fluorescence emission was read at 545 nm after exitation at 270 nm. The limits of quantification (LOQ) and detection (LOD) were 0.26 and 0.08 nM, respectively. The method was used to detect DPA extracted from Bacillus subtilis endospores, DPA extracted from B. subtilis endospores added to more complex substrates such as marine sediment and canned tuna and DPA extracted from indigenous endospores in a coastal marine sediment. Endospores represented 4% of the microbial community (bacterial cells + endospores) in active surface sediment from the Aarhus Bay.
GEOTRACES intercalibration of neodymium isotopes and rare earth element concentrations in seawater and suspended particles. Part 2: Systematic tests and baseline profiles
Authors: Pahnke Katharina , van de Flierdt Tina , Jones Kevin M. , Lambelet Myriam , Hemming Sidney R. , Goldstein Steven L.
Published: May 2012

The large‐scale collection of seawater samples and analysis of trace elements and isotopes by the GEOTRACES program call for careful comparison and examination of different methods for sample collection, treatment, and processing. Here we report results for different filter types, sampling bottles, and preconcentration methods for Nd from seawater. Neodymium isotope ratios and concentrations of unfiltered and filtered seawater using five different filter types agree within 43‐56 ppm (2σ standard deviation, SD) and 10% (relative 2σ standard deviation), respectively. The filter choice therefore has no effect on the measured parameters at the studied locations in the western North Atlantic. This could well be different, however, in areas of high particle concentrations. We therefore strongly recommend filtration of seawater for Nd isotope and rare earth element concentration measurements. Dissolved 143Nd/144Nd ratios of seawater collected with Niskin bottles with internal nylon‐coated stainless steel springs and trace metal‐clean GO‐FLO bottles were the same within 43 ppm (2σ SD). The Niskin bottles used here are therefore suitable for the collection of seawater samples for the analysis of 143Nd/144Nd ratios. Iron coprecipitation and complexation with HDEHP/H2MEHP using C18 cartridges for the preconcentration of Nd from seawater yielded the same 143Nd/144Nd ratios within 37 ppm (2σ SD). Both methods are therefore appropriate. Water column profiles of 143Nd/144Nd ratios and Nd concentrations are reported for the North Atlantic (BATS) and North Pacific (SAFe), and profiles of all rare earth elements are reported for BATS. These baseline profiles are recommended for continued quality control and intercalibration by future GEOTRACES cruises.
Intercalibration of Cd and Pb concentration measurements in the northwest Pacific Ocean
Authors: Zurbrick C. M. , Morton P. L. , Gallon C. , Shiller A. M. , Landing W.M. , Flegal A.R.
Published: May 2012

Dissolved and total Cd and Pb concentration measurements in seawater were intercalibrated using 33 samples collected on the fourth cruise of the Intergovernmental Oceanographic Commission's (IOC‐4) Global Investigation of Pollution in the Marine Environment (GIPME) in the northwest Pacific Ocean, as well as in three seawater reference materials (SAFe S1, SAFe D2, and NASS‐5). Laboratories from Florida State University (FSU), University of California at Santa Cruz (UCSC), and University of Southern Mississippi (USM) participated in the Pb intercalibration, and two of them (FSU and UCSC) participated in the Cd intercalibration. While each of the laboratories employed different extraction techniques before analysis by inductively coupled plasma—mass spectrometry (ICP‐MS), the measurements of Cd and Pb concentrations for the IOC‐4 samples agreed to within 4% and 15%, respectively, and those of the reference materials agreed to within 13% and 8%, respectively. This successful intercalibration demonstrates that there now are multiple techniques available for accurately measuring Cd and Pb concentrations in seawater.
Determination of 232Th and 230Th in seawater using a chemical separation procedure and thermal ionization mass spectrometry
Authors: Andersson Per S. , Schöberg Hans
Published: May 2012

A method for the determination of 232Th and 230Th in seawater has been developed by substantial modifications of available techniques mainly used for other matrixes. We use a well calibrated 229Th spike and iron oxyhydroxides as a carrier phase for the precipitation of Th from about 3.5 L filtered seawater. The chemical separation and purification of Th from the Fe carrier comprise three ion chromatography steps including AG 1‐x8 (200–400 mesh, Cl− form), TRU Resin, and UTEVA Resin. The separated Th fraction is loaded with a mixture of graphite/phosphoric acid onto zone‐refined single rhenium filaments. These are analyzed in peak‐jumping mode on a thermal ionization mass spectrometer. Due to the low Th concentration in seawater, the 232Th blank constitute a significant problem for the chemical separation of Th from the seawater matrix and also for the filament loading. By applying a detailed cleaning scheme including a HF‐HCl mixture, the total procedural blank could be substantially reduced to approximately 0.4 pg. This is generally < 1% of a typical 232Th concentration in surface seawater, which ranges from about 0.01 to 1 picomol/kg. The analysis of standards, artificial seawater, and a series of seawater samples obtained from the GEOTRACES intercalibration cruises in 2008 and 2009 demonstrate that this method can yield a precision for 232Th concentration in seawater of about 1% to 2% (2σ) and 230Th concentration of about 2% to 5% (2σ).
Analysis of stratospheric NO2 trends above Jungfraujoch using ground-based UV-visible, FTIR, and satellite nadir observations
Authors: Hendrick F. , Mahieu E. , Bodeker G. E. , Boersma K. F. , Chipperfield M. P. , De Mazière M. , De Smedt I. , Demoulin P. , Fayt C. , Hermans C. , Kreher K. , Lejeune B. , Pinardi G. , Servais C. , Stübi R. , van der A R. , Vernier J.-P. , Van Roozendael M.
Published: May 2012

Abstract. The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5° N, 8.0° E) is assessed using ground-based FTIR and zenith-scattered visible sunlight SAOZ measurements over the period 1990 to 2009 as well as a composite satellite nadir data set constructed from ERS-2/GOME, ENVISAT/SCIAMACHY, and METOP-A/GOME-2 observations over the 1996–2009 period. To calculate the trends, a linear least squares regression model including explanatory variables for a linear trend, the mean annual cycle, the quasi-biennial oscillation (QBO), solar activity, and stratospheric aerosol loading is used. For the 1990–2009 period, statistically indistinguishable trends of −3.7 ± 1.1%/decade and −3.6 ± 0.9%/decade are derived for the SAOZ and FTIR NO2 column time series, respectively. SAOZ, FTIR, and satellite nadir data sets show a similar decrease over the 1996–2009 period, with trends of −2.4 ± 1.1%/decade, −4.3 ± 1.4%/decade, and −3.6 ± 2.2%/decade, respectively. The fact that these declines are opposite in sign to the globally observed +2.5%/decade trend in N2O, suggests that factors other than N2O are driving the evolution of stratospheric NO2 at northern mid-latitudes. Possible causes of the decrease in stratospheric NO2 columns have been investigated. The most likely cause is a change in the NO2/NO partitioning in favor of NO, due to a possible stratospheric cooling and a decrease in stratospheric chlorine content, the latter being further confirmed by the negative trend in the ClONO2 column derived from FTIR observations at Jungfraujoch. Decreasing ClO concentrations slows the NO + ClO → NO2 + Cl reaction and a stratospheric cooling slows the NO + O3 → NO2 + O2 reaction, leaving more NOx in the form of NO. The slightly positive trends in ozone estimated from ground- and satellite-based data sets are also consistent with the decrease of NO2 through the NO2 + O3 → NO3 + O2 reaction. Finally, we cannot rule out the possibility that a strengthening of the Dobson-Brewer circulation, which reduces the time available for N2O photolysis in the stratosphere, could also contribute to the observed decline in stratospheric NO2 above Jungfraujoch.
Implications of all season Arctic sea-ice anomalies on the stratosphere
Authors: Cai D. , Dameris M. , Garny H. , Runde T.
Published: May 2012

Abstract. In this study the impact of a substantially reduced Arctic sea-ice cover on the lower and middle stratosphere is investigated. For this purpose two simulations with fixed boundary conditions (the so-called time-slice mode) were performed with a Chemistry-Climate Model. A reference time-slice with boundary conditions representing the year 2000 is compared to a second sensitivity simulation in which the boundary conditions are identical apart from the polar sea-ice cover, which is set to represent the years 2089–2099. Three features of Arctic air temperature response have been identified which are worth to be discussed in detail. Firstly, tropospheric mean polar temperatures increase up to 7 K during winter. This warming is primarily driven by changes in outgoing long-wave radiation. Secondly, temperatures decrease significantly in the summer stratosphere caused by a decline in outgoing short-wave radiation, accompanied by a characteristic increase of ozone mixing ratios. Thirdly, there are short periods of statistical significant temperature anomalies in the winter stratosphere probably driven by modified planetary wave activity. Both the internal as well as the inter-annual variability of Arctic sea-ice content is related to Arctic climatic fields like surface air temperature, sea level pressure or precipitation, which are analogue with the variability of the Arctic Oscillation (AO)-index. In this study significant changes in the AO-index are detected in the course of winter. Neutral phases of AO appear more often. As expected, the dominating dynamical response of the stratosphere during winter turned out to be consistent to alterations in the tropospheric AO, although it is not statistically significant most of the time.
On the skill of various ensemble spread estimators for probabilistic short range wind forecasting
Authors: Kann A.
Published: May 2012

Abstract. A variety of applications ranging from civil protection associated with severe weather to economical interests are heavily dependent on meteorological information. For example, a precise planning of the energy supply with a high share of renewables requires detailed meteorological information on high temporal and spatial resolution. With respect to wind power, detailed analyses and forecasts of wind speed are of crucial interest for the energy management. Although the applicability and the current skill of state-of-the-art probabilistic short range forecasts has increased during the last years, ensemble systems still show systematic deficiencies which limit its practical use. This paper presents methods to improve the ensemble skill of 10-m wind speed forecasts by combining deterministic information from a nowcasting system on very high horizontal resolution with uncertainty estimates from a limited area ensemble system. It is shown for a one month validation period that a statistical post-processing procedure (a modified non-homogeneous Gaussian regression) adds further skill to the probabilistic forecasts, especially beyond the nowcasting range after +6 h.
A mechanism for dust-induced destabilization of glacial climates
Authors: Farrell B. F. , Abbot D. S.
Published: May 2012

Abstract. Abrupt transitions between cold/dry stadial and warm/wet interstadial states occurred during glacial periods in the absence of any known external forcing. The climate record preserved in polar glaciers, mountain glaciers, and widespread cave deposits reveals that these events were global in extent with temporal distribution implying an underlying memoryless process with millennial time scale. Here a theory is advanced implicating feedback between atmospheric dust and the hydrological cycle in producing these abrupt transitions. Calculations are performed using a radiative-convective model that includes the interaction of aerosols with radiation to reveal the mechanism of this dust/precipitation interaction feedback process and a Langevin equation is used to illustrate qualitatively glacial climate destabilization by this mechanism. This theory explains the observed abrupt, bimodal, and memoryless nature of these transitions as well as their intrinsic connection with the hydrological cycle.
A new 100-m Digital Elevation Model of the Antarctic Peninsula derived from ASTER Global DEM: methods and accuracy assessment
Authors: Cook A. J. , Murray T. , Luckman A. , Vaughan D. G. , Barrand N. E.
Published: May 2012

Abstract. A high resolution surface topography Digital Elevation Model (DEM) is required to underpin studies of the complex glacier system on the Antarctic Peninsula. A complete DEM with better than 200 m pixel size and high positional and vertical accuracy would enable mapping of all significant glacial basins and provide a dataset for glacier morphology analyses. No currently available DEM meets this specification. We present a new 100-m DEM of the Antarctic Peninsula (63–70° S), based on ASTER Global Digital Elevation Model (GDEM) data. The raw GDEM products are of high-quality on the rugged terrain and coastal-regions of the Antarctic Peninsula and have good geospatial accuracy, but they also contain large errors on ice-covered terrain and we seek to minimise these artefacts. Conventional data correction techniques do not work so we have developed a method that significantly improves the dataset, smoothing the erroneous regions and hence creating a DEM with a pixel size of 100 m that will be suitable for many glaciological applications. We evaluate the new DEM using ICESat-derived elevations, and perform horizontal and vertical accuracy assessments based on GPS positions, SPOT-5 DEMs and the Landsat Image Mosaic of Antarctica (LIMA) imagery. The new DEM has a mean elevation difference of +3 m (±26 m RMSE) from ICESat, and a horizontal error of less than 2 pixels, although elevation accuracies are lower on mountain peaks and steep-sided slopes. The correction method significantly reduces errors on low relief slopes and therefore the DEM can be regarded as suitable for topographical studies such as measuring the geometry and ice flow properties of glaciers on the Antarctic Peninsula. The DEM is available for download from the NSIDC website: http://nsidc.org/data/dems/datasets.html (http://dx.doi.org/10.5060/D47P8W9D).
Technical Note: Downscaling RCM precipitation to the station scale using quantile mapping – a comparison of methods
Authors: Gudmundsson L. , Bremnes J. B. , Haugen J. E. , Engen Skaugen T.
Published: May 2012

Abstract. The impact of climate change on water resources is usually assessed at the local scale. However, regional climate models (RCM) are known to exhibit systematic biases in precipitation. Hence, RCM simulations need to be post-processed in order to produce reliable estimators of local scale climate. A popular post-processing approach is quantile mapping (QM), which is designed to adjust the distribution of modeled data, such that it matches observed climatologies. However, the diversity of suggested QM methods renders the selection of optimal techniques difficult and hence there is a need for clarification. In this paper, QM methods are reviewed and classified into: (1) distribution derived transformations, (2) parametric transformations and (3) nonparametric transformations; each differing with respect to their underlying assumptions. A real world application, using observations of 82 precipitation stations in Norway, showed that nonparametric transformations have the highest skill in systematically reducing biases in RCM precipitation.