bluuebunny/crossref_metadata_2025 huggingface dataset:
Results and risk factors for recurrence following single-level tubular lumbar microdiscectomy
Authors: Moliterno Jennifer A. , Knopman Jared , Parikh Karishma , Cohan Jessica N. , Huang Q. Daisy , Aaker Grant D. , Grivoyannis Anastasia D. , Patel Ashwin R. , Härtl Roger , Boockvar John A.
Published: June 2010

Object

The use of minimally invasive surgical techniques, including microscope-assisted tubular lumbar microdiscectomy (tLMD), has gained increasing popularity in treating lumbar disc herniations (LDHs). This particular procedure has been shown to be both cost-efficient and effective, resulting in outcomes comparable to those of open surgical procedures. Lumbar disc herniation recurrence necessitating reoperation, however, remains an issue following spinal surgery, with an overall reported incidence of approximately 3–13%. The authors' aim in the present study was to report their experience using tLMD for single-level LDH, hoping to provide further insight into the rate of surgical recurrence and to identify potential risk factors leading to this complication.

Methods

The authors retrospectively reviewed the cases of 217 patients who underwent tLMD for single-level LDH performed identically by 2 surgeons (J.B., R.H.) between 2004 and 2008. Evaluation for LDH recurrence included detailed medical chart review and telephone interview. Recurrent LDH was defined as the return of preoperative signs and symptoms after an interval of postoperative resolution, in conjunction with radiographic demonstration of ipsilateral disc herniation at the same level and pathological confirmation of disc material. A cohort of patients without recurrence was used for comparison to identify possible risk factors for recurrent LDH.

Results

Of the 147 patients for whom the authors were able to definitively assess symptomatic recurrence status, 14 patients (9.5%) experienced LDH recurrence following single-level tLMD. The most common level involved was L5–S1 (42.9%) and the mean length of time to recurrence was 12 weeks (range 1.5–52 weeks). Sixty-four percent of the patients were male. In a comparison with patients without recurrence, the authors found that relatively lower body mass index was significantly associated with recurrence (p = 0.005), such that LDH in nonobese patients was more likely to recur.

Conclusions

Recurrence rates following tLMD for LDH compare favorably with those in patients who have undergone open discectomy, lending further support for its effectiveness in treating single-level LDH. Nonobese patients with a relatively lower body mass index, in particular, appear to be at greater risk for recurrence.
Unfree Verse: John Wilkinson's The Speaking Twins
Authors: Jarvis Simon
Published: June 2010

This essay revisits the relationship between philosophy and poetry. It argues that a crucial term, ‘verse’, is often missing from discussion of that relationship. The broader term, ‘poetry’, is so difficult to define that it offers insufficient specific resistance to large philosophical schemas. The question is explored here through an analysis of the prosodic microstructures in John Wilkinson's The Speaking Twins. I conclude that Wilkinson's poem is an instance of ‘unfree verse’ (in a sense which I define in the essay) and that the poem's verse technique is also the site of its historical truth-content.
Delineating Grassland Bird Conservation Areas in the U.S. Prairie Pothole Region
Authors: Johnson Rex R. , Granfors Diane A. , Niemuth Neal D. , Estey Michael E. , Reynolds Ronald E.
Published: June 2010

Conservation of birds is increasingly focused on the importance of landscape characteristics to sustain populations. Implementing conservation on a landscape scale requires reliable spatial models that provide biological context for conservation actions. Before species-specific models relating grassland birds to their habitat at landscape scales existed, we created a conceptual model and applied it to spatial data to identify priority grassland habitats for the protection and restoration of populations of area sensitive grassland birds in the Prairie Pothole Region. Since that time, these Grassland Bird Conservation Areas have been widely used to guide conservation, and variations of these models have been adopted in other regions; however, the process used to delineate them (i.e., the conceptual models) is poorly understood by many users. We describe that process here and offer perspectives on the utility and limitations of conceptual models, especially on the value of making assumptions that commonly underlie management decisions explicitly, thereby making the assumptions testable, and hopefully increasing management transparency, credibility, and efficiency.
Umbilical Cord Blood T Cells Respond against the Melan-A/MART-1 Tumor Antigen and Exhibit Reduced Alloreactivity as Compared with Adult Blood-Derived T Cells
Authors: Merindol Natacha , Grenier Anne-Julie , Caty Martine , Charrier Emily , Duval Arnaud , Duval Michel , Champagne Martin A. , Soudeyns Hugo
Published: June 2010

Umbilical cord blood (UCB) is increasingly used as a source of hematopoietic progenitor cells to treat a variety of disorders. UCB transplant is associated with comparatively reduced incidence of graft-versus-host disease, robust graft versus leukemia effect, and relatively high incidence of opportunistic infections, three processes in which donor-derived T lymphocytes are known to be predominantly involved. To examine the differential functionality of UCB T cells, CD8+ T cells specific for the melanoma-associated HLA-A2–restricted Melan-A26–35 A27L peptide were isolated from HLA-A2+ and HLA-A2− UCB samples and HLA-A2+ and HLA-A2− adult peripheral blood using A2/Melan-A tetramers. In UCB samples, A2/Melan-A+ CD8+ T cells were detected at a frequency of 0.04%, were more frequent in HLA-A2+ UCB, and were polyclonal and mostly naive. Consistent with Ag-driven expansion, the frequency of A2/Melan-A+ CD8+ T cells was increased following stimulation with cognate peptide or polyclonal activation, they acquired cell-surface markers reflective of effector/memory differentiation, their TCR repertoire became oligoclonal, and they expressed cytolytic activity and produced IFN-γ. Although functional properties of A2/Melan-A+ CD8+ T cells derived from HLA-A2+ UCB resembled those of HLA-A2+ adult peripheral blood, they were more likely to reach terminal differentiation following polyclonal stimulation and produced less IFN-γ in response to cognate peptide. A2/Melan-A+ CD8+ T cells from HLA-A2− UCB were poorly cytolytic, produced little IFN-γ, and were predominantly monofunctional or nonfunctional. These properties of UCB-derived CD8+ T cells could contribute to the reduced incidence of graft-versus-host disease and heightened incidence of opportunistic infections observed following UCB transplant.
The Relative Timing of Exposure to Phagocytosable Particulates and to Osteoclastogenic Cytokines Is Critically Important in the Determination of Myeloid Cell Fate
Authors: James Douglas E. , Nestor Bryan J. , Sculco Thomas P. , Ivashkiv Lionel B. , Ross F. Patrick , Goldring Steven R. , Purdue P. Edward
Published: June 2010

During granulomatous inflammatory reactions, myeloid cells can differentiate into activated phagocytic macrophages, wound-healing macrophages, foreign body giant cells, and bone-resorbing osteoclasts. Although it is appreciated that a variety of stimuli, including cytokines, cell–matrix interactions, and challenge with foreign materials can influence myeloid cell fate, little is known of how these signals integrate during this process. In this study, we have investigated the cross talk between receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis and particle phagocytosis-induced activation of human monocytes. Understanding interconnected signals is of particular importance to disorders, such as periprosthetic osteolysis, in which granulomatous inflammation is initiated by particle phagocytosis in proximity to bone and leads to inflammatory bone loss. Using cell-based osteoclastogenesis and phagocytosis assays together with expression analysis of key regulators of osteoclastogenesis, we show in this study that phagocytosis of disease-relevant particles inhibits RANKL-mediated osteoclastogenesis of human monocytes. Mechanistically, phagocytosis mediates this effect by downregulation of RANK and c-Fms, the receptors for the essential osteoclastogenic cytokines RANKL and M-CSF. RANKL pretreatment of monocytes generates preosteoclasts that are resistant to RANK downregulation and committed to osteoclast formation, even though they retain phagocytic activity. Thus, the relative timing of exposure to phagocytosable particulates and to osteoclastogenic cytokines is critically important in the determination of myeloid cell fate.
Enhancement of Antiviral Immunity by Small Molecule Antagonist of Suppressor of Cytokine Signaling
Authors: Ahmed Chulbul M. I. , Dabelic Rea , Martin James P. , Jager Lindsey D. , Haider S. Mohammad , Johnson Howard M.
Published: June 2010

Suppressors of cytokine signaling (SOCSs) are negative regulators of both innate and adaptive immunity via inhibition of signaling by cytokines such as type I and type II IFNs. We have developed a small peptide antagonist of SOCS-1 that corresponds to the activation loop of JAK2. SOCS-1 inhibits both type I and type II IFN activities by binding to the kinase activation loop via the kinase inhibitory region of the SOCS. The antagonist, pJAK2(1001–1013), inhibited the replication of vaccinia virus and encephalomyocarditis virus in cell culture, suggesting that it possesses broad antiviral activity. In addition, pJAK2(1001–1013) protected mice against lethal vaccinia and encephalomyocarditis virus infection. pJAK2(1001–1013) increased the intracellular level of the constitutive IFN-β, which may play a role in the antagonist antiviral effect at the cellular level. Ab neutralization suggests that constitutive IFN-β may act intracellularly, consistent with recent findings on IFN-γ intracellular signaling. pJAK2(1001–1013) also synergizes with IFNs as per IFN-γ mimetic to exert a multiplicative antiviral effect at the level of transcription, the cell, and protection of mice against lethal viral infection. pJAK2(1001–1013) binds to the kinase inhibitory region of both SOCS-1 and SOCS-3 and blocks their inhibitory effects on the IFN-γ activation site promoter. In addition to a direct antiviral effect and synergism with IFN, the SOCS antagonist also exhibits adjuvant effects on humoral and cellular immunity as well as an enhancement of polyinosinic-polycytidylic acid activation of TLR3. The SOCS antagonist thus presents a novel and effective approach to enhancement of host defense against viruses.
Mechanism and Localization of CD8 Regulatory T Cells in a Heart Transplant Model of Tolerance
Authors: Li Xian Liang , Ménoret Séverine , Bezie Séverine , Caron Lise , Chabannes Dominique , Hill Marcelo , Halary Franck , Angin Mathieu , Heslan Michèle , Usal Claire , Liang Liang , Guillonneau Carole , Le Mauff Brigitte , Cuturi Maria Cristina , Josien Régis , Anegon Ignacio
Published: June 2010

Despite accumulating evidence for the importance of allospecific CD8+ regulatory T cells (Tregs) in tolerant rodents and free immunosuppression transplant recipients, mechanisms underlying CD8+ Treg-mediated tolerance remain unclear. By using a model of transplantation tolerance mediated by CD8+ Tregs following CD40Ig treatment in rats, in this study, we show that the accumulation of tolerogenic CD8+ Tregs and plasmacytoid dendritic cells (pDCs) in allograft and spleen but not lymph nodes was associated with tolerance induction in vascularized allograft recipients. pDCs preferentially induced tolerogenic CD8+ Tregs to suppress CD4+ effector cells responses to first-donor Ags in vitro. When tolerogenic CD8+ Tregs were not in contact with CD4+ effector cells, suppression was mediated by IDO. Contact with CD4+ effector cells resulted in alternative suppressive mechanisms implicating IFN-γ and fibroleukin-2. In vivo, both IDO and IFN-γ were involved in tolerance induction, suggesting that contact with CD4+ effector cells is crucial to modulate CD8+ Tregs function in vivo. In conclusion, CD8+ Tregs and pDCs interactions were necessary for suppression of CD4+ T cells and involved different mechanisms modulated by the presence of cell contact between CD8+ Tregs, pDCs, and CD4+ effector cells.
Low-Level Exposure to HIV Induces Virus-Specific T Cell Responses and Immune Activation in Exposed HIV-Seronegative Individuals
Authors: Restrepo Clara , Rallón Norma I. , del Romero Jorge , Rodríguez Carmen , Hernando Victoria , López Mariola , Peris Alejandra , Lozano Sara , Sempere-Ortells José M. , Soriano Vincent , Benito José M.
Published: June 2010

HIV-specific T cells response and T cell activation are frequently seen in exposed seronegative individuals (ESN). In this study, we report HIV-specific response and level of T cell activation in ESN partners of HIV-infected patients presenting low or undetectable levels of HIV-RNA. We evaluated 24 HIV-serodiscordant couples. ESN were classified into three categories of exposure to HIV (very low, low, and moderate-high), considering levels of HIV-RNA in their infected partner and frequency of sexual high-risk practices within the last 12 mo. HIV-specific T cell responses and activation levels in T cell subsets were evaluated by flow cytometry. We reported that 54% of ESN had detectable HIV-specific T cells response, being the highest prevalence seen in the low exposure group (64%). Several T cell subsets were significantly increased in ESN when compared with controls: CD4+CD38+ (p = 0.006), CD4+HLA-DR−CD38+ (p = 0.02), CD4+CD45RA+CD27+HLA-DR−CD38+ (p = 0.002), CD8+CD45RA+CD27+CD38−HLA-DR+ (p = 0.02), and CD8+CD45RA+CD27−CD38+HLA-DR+ (p = 0.03). Activation of CD8+ T cells was increased in ESN with detectable HIV T cell responses compared with ESN lacking these responses (p = 0.04). Taken together, these results suggest that persistent but low sexual HIV exposure is able to induce virus-specific T cells response and immune activation in a high proportion of ESN, suggesting that virus exposure may occur even in conditions of maximal viral suppression in the HIV-infected partner.
The Exocytosis of Lytic Granules Is Impaired in Vti1b- or Vamp8-Deficient CTL Leading to a Reduced Cytotoxic Activity following Antigen-Specific Activation
Authors: Dressel Ralf , Elsner Leslie , Novota Peter , Kanwar Namita , Fischer von Mollard Gabriele
Published: June 2010

The exocytosis of cytotoxic proteins stored in lytic granules of activated CTL is a key event during killing of target cells. Membrane fusion events that are mediated by soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins are crucial, as demonstrated by patients with familial hemophagocytic lymphohistocytosis type 4 who have mutations in the SNARE protein syntaxin-11 that result in an impaired degranulation of cytotoxic cells. We found an increased mRNA expression of the SNARE protein genes Vti1b and Vamp8 during Ag-specific activation of CTL from TCR-transgenic OT-I mice. Therefore, we investigated the cytolytic activity of CTL from TCR-transgenic Vti1b and Vamp8 knockout mice. At 3 d as well as at 4 d of Ag-specific stimulation, the degranulation of CTL was significantly reduced in Vti1b and Vamp8 knockout mice, as determined by cell surface expression of the degranulation marker CD107a. After 3 d of Ag-specific stimulation, the cytolytic activity of Vti1b- and Vamp8-deficient CTL was reduced to ≈50% compared with heterozygous controls. However, 4 d after stimulation, the cytotoxic activity of Vti1b- as well as Vamp8-deficient CTL was not impaired anymore. The capacity of Vti1b- and Vamp8-deficient dendritic cells to process Ags and to stimulate the proliferation of CTL was not reduced, arguing against an indirect effect on the activation of CTL. These findings suggest a role of the SNARE proteins vti1b and vesicle-associated membrane protein 8 in the degranulation of CTL. However, a deficiency can apparently be compensated and affects only transiently the cytotoxic activity of CTL during their development to armed effector cells.
Suppressor of Cytokine Signaling 2 Regulates IL-15–Primed Human NK Cell Function via Control of Phosphorylated Pyk2
Authors: Lee Suk Hyung , Yun Sohyun , Piao Zheng-Hao , Jeong Mira , Kim Dong Oh , Jung Haiyoung , Lee Jiwon , Kim Mi Jeong , Kim Mi Sun , Chung Jin Woong , Kim Tae-Don , Yoon Suk Ran , Greenberg Philip D. , Choi Inpyo
Published: June 2010

NK cells are capable of killing virus-infected or tumor cells and producing IFN-γ. Resting NK cells, however, have only minimal cytolytic activity and secrete a low level of IFN-γ. The cytokine IL-15 can promote the expression of effector functions by resting NK cells. In this study, we demonstrate that suppressor of cytokine signaling 2 (SOCS2) has a novel role in IL-15–primed human NK cell function. SOCS2 expression was upregulated in NK cells following stimulation with IL-15. During IL-15–mediated NK cell priming, SOCS2 interacted with phosphorylated proline-rich tyrosine kinase 2 (Pyk2) at tyrosine 402 (p-Pyk2Tyr402) and induced the proteasome-mediated degradation of p-Pyk2Tyr402 via ubiquitination. Knockdown of SOCS2 resulted in the accumulation of p-Pyk2Tyr402 and blocked NK cell effector functions. In addition, NK cell cytolytic activity and IFN-γ production were inhibited by overexpression of the wild-type of Pyk2 but not by the overexpression of tyrosine 402 mutant of Pyk2. These results suggest that SOCS2 regulates human NK cell effector functions via control of phosphorylated Pyk2 depending on IL-15 existence.
Long Peptide Vaccination Can Lead to Lethality through CD4+ T Cell-Mediated Cytokine Storm
Authors: Kitamura Hiroshi , Sedlik Christine , Jacquet Alexandra , Zaragoza Bruno , Dusseaux Mathilde , Premel Virginie , Sastre-Garau Xavier , Lantz Olivier
Published: June 2010

The optimization of anticancer therapeutic vaccines can lead to better efficacy but also to stronger adverse effects. In a mouse model of antitumor vaccination using a long peptide (LP), which included MHC class I- and II-restricted male (H-Y) epitopes, we observed unexpected mortality. Mice with an increased frequency of anti–H-Y CD4 T cells were primed with LP+CpG and boosted 10 d later. Within hours of boost, they displayed shock-like signs with high mortality. Serum cytokine levels were high. TNF-α secreted by the CD4 T cells was identified as the key effector molecule. Priming with a short peptide (SP), which included the MHC class II-restricted epitope, was a more efficient primer than LP, but did not lead to mortality when used as boost. The high mortality induced by LP compared with SP was probably related to its specific ability to be presented by B cells. Finally, targeting the LP sequence to dendritic cells allowed tumor protection without side effects. Our data: 1) confirm that the immune system can be very dangerous; 2) caution against the use of systemic activation of high-frequency Ag-specific T cells as induced by high doses of LP; and 3) underline the benefit of targeting Ag to dendritic cells.
Clinical history of HIV infection may be misleading in cytopathology
Authors: Pantanowitz* Liron , Kuperman Michael , Goulart Robert A.
Published: June 2010

Human immunodeficiency virus (HIV)-infected patients are at an increased risk for developing opportunistic infections, reactive conditions and neoplasms. As a result, a broad range of conditions are frequently included in the differential diagnosis of HIV-related lesions. The clinical history of HIV infection may, however, be misleading in some cases. Illustrative cases are presented in which knowledge of a patient's HIV status proved to be misleading and increased the degree of complexity of the cytologic evaluation. Case 1 involved the fine needle aspiration (FNA) of a painful 3 cm unilateral neck mass in a 38-year-old female with generalized lymphadenopathy. Her aspirate revealed a spindle cell proliferation devoid of mycobacteria that was immunoreactive for S-100 and macrophage markers (KP-1, PGM1). Multiple noncontributory repeat procedures were performed until a final excision revealed a schwannoma. Case 2 was a CT-guided FNA of a positron emission tomography positive lung mass in a 53-year-old man. The acellular aspirate in this case contained structures resembling fungal spore forms that were negative for mucicarmine and GMS stains, as well as cryptococcal antigen immunocytochemistry. A Von Kossa stain confirmed that these pseudo-fungal structures were calcified debris. Follow up revealed multiple calcified lung and hilar node based granulomata. Case 3 involved the cytologic evaluation of pleural fluid from a 47-year-old man with Kaposi sarcoma and recurrent chylous pleural effusions. Large atypical cells identified in his effusion were concerning for primary effusion lymphoma. Subsequent pleural biopsy revealed extramedullary hematopoiesis, documenting these atypical cells as megakaryocytes. These cases demonstrate that knowledge of a patient's HIV status can be misleading in the evaluation of cytology specimens, with potential for misdiagnosis and/or multiple procedures. To avoid this pitfall in the setting of HIV infection, common entities unrelated to HIV infection and artifacts should always be included in the differential diagnosis.
Atypical squamous cells, cannot exclude high grade squamous intraepithelial (ASC-H) in HIV-positive women
Authors: Michelow* Pam , Hartman Ingrid , Schulze Doreen , Lamla-Hillie Stella , Williams Sophie , Levin Simon , Firnhaber Cynthia
Published: June 2010

Objective:

South Africa has very high rates of both HIV infection and cervical pathology. The management of ASC-H is colposcopy and directed biopsy, but with so many women diagnosed with HSIL and a dearth of colposcopy centres in South Africa, women with cytologic diagnosis of ASC-H may not be prioritized for colposcopy. The aim of this study was to determine if HIV-positive women with a cytologic diagnosis of ASC-H should undergo immediate colposcopy or whether colposcopy can be delayed, within the context of an underfunded health care setting with so many competing health needs.

Materials and Methods:

A computer database search was performed from the archives of an NGO-administered clinic that offers comprehensive HIV care. All women with a cytologic diagnosis of ASC-H on cervical smears from September 2005 until August 2009 were identified. Histologic follow up was sought in all patients.

Results:

A total of 2111 cervical smears were performed and 41 diagnosed as ASC-H (1.94%). No histologic follow up data was available in 15 cases. Follow up histologic results were as follows: three negative (11.5%), five koilocytosis and/ or CIN1 (19.2%), ten CIN2 (38.5%) and eight CIN3 (30.8%). There were no cases of invasive carcinoma on follow up.

Conclusion:

The current appropriate management of HIV-positive women in low-resource settings with a diagnosis of ASC-H on cervical smear is colposcopy, despite the costs involved. In the future and if cost-effective in developing nations, use of novel markers may help select which HIV-positive women can be managed conservatively and which ones referred for more active treatment. More research in this regard is warranted.
Representing a Product System Representation as a Contractive Semigroup and Applications to Regular Isometric Dilations
Authors: Shalit Orr Moshe
Published: June 2010

In this paper we propose a new technical tool for analyzing representations of Hilbert C*- product systems. Using this tool, we give a new proof that every doubly commuting representation over ℕk has a regular isometric dilation, and we also prove sufficient conditions for the existence of a regular isometric dilation of representations over more general subsemigroups of .
On the Negative Index Theorem for the Linearized Non-Linear Schrödinger Problem
Authors: Vougalter Vitali
Published: June 2010

A new and elementary proof is given of the recent result of Cuccagna, Pelinovsky, and Vougalter based on the variational principle for the quadratic form of a self-adjoint operator. It is the negative index theorem for a linearized NLS operator in three dimensions.
Time derivative of the horizontal geomagnetic field as an activity indicator
Authors: Viljanen A. , Nevanlinna H. , Pajunpää K. , Pulkkinen A.
Published: June 2010

Abstract. Geomagnetically induced currents (GICs) in technological conductor systems are a manifestation of the ground effects of space weather. Large GICs are always associated with large values of the time derivative of the geomagnetic field, and especially with its horizontal component (dH/dt). By using the IMAGE magnetometer data from northern Europe from 1982 to 2001, we show that large dH/dt’s (exceeding 1 nT/s) primarily occur during events governed by westward ionospheric currents. However, the directional distributions of dH/dt are much more scattered than those of the simultaneous baseline subtracted horizontal variation field vector ΔH. A pronounced difference between ΔH and dH/dt takes place at about 02–06 MLT in the auroral region when dH/dt prefers an east-west orientation, whereas ΔH points to the south. The occurrence of large dH/dt has two daily maxima, one around the local magnetic midnight, and another in the morning. There is a single maximum around the midnight only at the southernmost IMAGE stations. An identical feature is observed when large GICs are considered. The yearly number of large dH/dt values in the auroral region follows quite closely the aa index, but a clear variation from year-to-year is observed in the directional distributions. The scattering of dH/dt distributions is smaller during descending phases of the sunspot cycle. Seasonal variations are also seen, especially in winter dH/dt  is more concentrated to the north-south direction than at other times. The results manifest the importance of small-scale structures of ionospheric currents when GICs are considered. The distribution patterns of dH/dt cannot be explained by any simple sheet-type model of (westward) ionospheric currents, but rapidly changing north-south currents and field-aligned currents must play an important role.Key words. Geomagnetism and paleomagnetism (geomagnetic induction; rapid time variations) - Ionosphere (ionospheric disturbances)
Drifter dispersion in the Adriatic Sea: Lagrangian data and chaotic model
Authors: Lacorata G. , Aurell E. , Vulpiani A.
Published: June 2010

Abstract. We analyze characteristics of drifter trajectories from the Adriatic Sea with recently introduced nonlinear dynamics techniques. We discuss how in quasi-enclosed basins, relative dispersion as a function of time, a standard analysis tool in this context, may give a distorted picture of the dynamics. We further show that useful information may be obtained by using two related non-asymptotic indicators, the Finite-Scale Lyapunov Exponent (FSLE) and the Lagrangian Structure Function (LSF), which both describe intrinsic physical properties at a given scale. We introduce a simple chaotic model for drifter motion in this system, and show by comparison with the model that Lagrangian dispersion is mainly driven by advection at sub-basin scales until saturation sets in.Key words. Oceanography: General (marginal and semi-closed seas) – Oceanography: Physical (turbulence, diffusion, and mixing processes; upper ocean processes)
Active spacecraft potential control for Cluster – implementation and first results
Authors: Torkar K. , Riedler W. , Escoubet C. P. , Fehringer M. , Schmidt R. , Grard R. J. L. , Arends H. , Rüdenauer F. , Steiger W. , Narheim B. T. , Svenes K. , Torbert R. , André M. , Fazakerley A. , Goldstein R. , Olsen R. C. , Pedersen A. , Whipple E. , Zhao H.
Published: June 2010

Abstract. Electrostatic charging of a spacecraft modifies the distribution of electrons and ions before the particles enter the sensors mounted on the spacecraft body. The floating potential of magnetospheric satellites in sunlight very often reaches several tens of volts, making measurements of the cold (several eV) component of the ambient ions impossible. The plasma electron data become contaminated by large fluxes of photoelectrons attracted back into the sensors. The Cluster spacecraft are equipped with emitters of the liquid metal ion source type, producing indium ions at 5 to 9 keV energy at currents of some tens of microampere. This current shifts the equilibrium potential of the spacecraft to moderately positive values. The design and principles of the operation of the instrument for active spacecraft potential control (ASPOC) are presented in detail. Experience with spacecraft potential control from the commissioning phase and the first two months of the operational phase are now available. The instrument is operated with constant ion current for most of the time, but tests have been carried out with varying currents and a "feedback" mode with the instrument EFW, which measures the spacecraft potential . That has been reduced to values according to expectations. In addition, the low energy electron measurements show substantially reduced fluxes of photoelectrons as expected. The flux decrease in photoelectrons returning to the spacecraft, however, occurs at the expense of an enlarged sheath around the spacecraft which causes problems for boom-mounted probes.Key words. Space plasma physics (spacecraft sheaths, wakes, charging); Instruments and techniques; Active perturbation experiments
Four-point high time resolution information on electron densities by the electric field experiments (EFW) on Cluster
Authors: Pedersen A. , Décréau P. , Escoubet C.-P. , Gustafsson G. , Laakso H. , Lindqvist P.-A. , Lybekk B. , Masson A. , Mozer F. , Vaivads A.
Published: June 2010

Abstract. For accurate measurements of electric fields, spherical double probes are electronically controlled to be at a positive potential of approximately 1 V relative to the ambient magnetospheric plasma. The spacecraft will acquire a potential which balances the photoelectrons escaping to the plasma and the electron flux collected from the plasma. The probe-to-plasma potential difference can be measured with a time resolution of a fraction of a second, and provides information on the electron density over a wide range of electron densities from the lobes (~ 0.01 cm-3) to the magnetosheath (>10 cm-3) and the plasmasphere (>100 cm-3). This technique has been perfected and calibrated against other density measurements on GEOS, ISEE-1, CRRES, GEOTAIL and POLAR. The Cluster spacecraft potential measurements opens the way for new approaches, particularly near boundaries and gradients where four-point measurements will provide information never obtained before. Another interesting point is that onboard data storage of this simple parameter can be done for complete orbits and thereby will provide background information for the shorter full data collection periods on Cluster. Preliminary calibrations against other density measurements on Cluster will be reported.Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers) Space plasma physics (spacecraft sheaths, wakes, charging; instruments and techniques)
A classification of spectral populations observed in HF radar backscatter from the E region auroral electrojets
Authors: Milan S. E. , Lester M.
Published: June 2010

Abstract. Observations of HF radar backscatter from the auroral electrojet E region indicate the presence of five major spectral populations, as opposed to the two predominant spectral populations, types I and II, observed in the VHF regime. The Doppler shift, spectral width, backscatter power, and flow angle dependencies of these five populations are investigated and described. Two of these populations are identified with type I and type II spectral classes, and hence, are thought to be generated by the two-stream and gradient drift instabilities, respectively. The remaining three populations occur over a range of velocities which can greatly exceed the ion acoustic speed, the usual limiting velocity in VHF radar observations of the E region. The generation of these spectral populations is discussed in terms of electron density gradients in the electrojet region and recent non-linear theories of E region irregularity generation.Key words. Ionosphere (ionospheric irregularities)
CUTLASS HF radar observations of high-velocity E-region echoes
Authors: Uspensky M. V. , Koustov A. V. , Eglitis P. , Huuskonen A. , Milan S. E. , Pulkkinen T. , Pirjola R.
Published: June 2010

Abstract. A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms–1 , while the other group had significantly larger velocities, of the order of 700 ms–1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms–1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms–1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm–1 ) and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere)
Evidence for thermospheric gravity waves in the southern polar cap from ground-based vertical velocity and photometric observations
Authors: Innis J. L. , Greet P. A. , Dyson P. L.
Published: June 2010

Abstract. Zenith-directed Fabry-Perot Spectrometer (FPS) and 3-Field Photometer (3FP) observations of the λ630 nm emission (~240 km altitude) were obtained at Davis station, Antarctica, during the austral winter of 1999. Eleven nights of suitable data were searched for significant periodicities common to vertical winds from the FPS and photo-metric variations from the 3FP. Three wave-like events were found, each of around one or more hours in duration, with periods around 15 minutes, vertical velocity amplitudes near 60 ms–1 , horizontal phase velocities around 300 ms–1 , and horizontal wavelengths from 240 to 400 km. These characteristics appear consistent with polar cap gravity waves seen by other workers, and we conclude this is a likely interpretation of our data. Assuming a source height near 125 km altitude, we determine the approximate source location by calculating back along the wave trajectory using the gravity wave property relating angle of ascent and frequency. The wave sources appear to be in the vicinity of the poleward border of the auroral oval, at magnetic local times up to 5 hours before local magnetic midnight.Key words. Meteorology and atmospheric dynamics (thermospheric dynamics; waves and tides)
LINDA – the Astrid-2 Langmuir probe instrument
Authors: Holback B. , Jacksén Å. , Åhlén L. , Jansson S.-E. , Eriksson A. I. , Wahlund J.-E. , Carozzi T. , Bergman J.
Published: June 2010

Abstract. The Swedish micro-satellite Astrid-2, designed for studies in magnetosperic physics, was launched into orbit on 10 December 1998 from the Russian cosmodrome Plesetsk. It was injected into a circular orbit at 1000 km and at 83 degrees inclination. The satellite carried, among other instruments, a double Langmuir Probe instrument called LINDA (Langmuir INterferometer and Density instrument for Astrid-2). The scientific goals of this instrument, as well as the technical design and possible modes of operation, are described. LINDA consists of two lightweight deployable boom systems, each carrying a small spherical probe. With these probes, separated by 2.9 meters, and in combination with a high sampling rate, it was possible to discriminate temporal structures (waves) from spatial structures. An on-board memory made it possible to collect data also at times when there was no ground contact. Plasma density and electron temperature data from all magnetic latitudes and for all seasons have been collected.Key words. Ionosphere (plasma temperature and density; plasma waves and instabilities; instruments and techniques)
Driven reconnection and bursty bulk flows
Authors: Pandey B. P. , Lakhina G. S.
Published: June 2010

Abstract. The energetics of driven magnetic reconnections induced by the deformation of the magnetopause boundary due to the solar wind-magnetosphere interaction are studied. The bursty type reconnection ensues due to the forcing of the magnetopause boundary by the solar wind. For typical plasma parameters in the inner central plasma sheet (ICPS), the magnetic energy release during the reconnection is estimated and it is found that the available free energy is comparable to the observed kinetic energy of typical bursty bulk flows. It implies that the part of the free energy goes into the heating of the ICPS particles, whereas the rest goes into its acceleration. The accelerated particle manifests itself as bursty flows.Key words. Magnetospheric physics (magnetotail; storms and substorms)
Precipitating clouds observed by 1.3-GHz boundary layer radars in equatorial Indonesia
Authors: Renggono F. , Hashiguchi H. , Fukao S. , Yamanaka M. D. , Ogino S.-Y. , Okamoto N. , Murata F. , Sitorus B. P. , Kudsy M. , Kartasasmita M. , Ibrahim G.
Published: June 2010

Abstract. Temporal variations of precipitating clouds in equatorial Indonesia have been studied based on observations with 1357.5 MHz boundary layer radars at Serpong (6.4° S, 106.7° E) near Jakarta and Bukittinggi (0.2° S, 100.3° E) in West Sumatera. We have classified precipitating clouds into four types: stratiform, mixed stratiform-convective, deep convective, and shallow convective clouds, using the Williams et al. (1995) method. Diurnal variations of the occurrence of precipitating clouds at Serpong and Bukittinggi have showed the same characteristics, namely, that the precipitating clouds primarily occur in the afternoon and the peak of the stratiform cloud comes after the peak of the deep convective cloud. The time delay between the peaks of stratiform and deep convective clouds corresponds to the life cycle of the mesoscale convective system. The precipitating clouds which occur in the early morning at Serpong are dominated by stratiform cloud. Concerning seasonal variations of the precipitating clouds, we have found that the occurrence of the stratiform cloud is most frequent in the rainy season, while the occurrence of the deep convective cloud is predominant in the dry season.Key words. Meteorology and atmospheric dynamics (convective processes; precipitation; tropical meteorology)
Seasonal variation of vertical eddy diffusivity in the troposphere, lower stratosphere and mesosphere over a tropical station
Authors: Narayana Rao D. , Ratnam M. V. , Rao T. N. , Rao S. V. B.
Published: June 2010

Abstract. Long-term VHF radar (53 MHz with 3° beam-width) observations at Gadanki (13.5° N, 79.2° E), India, during the period from September 1995 to August 1999 are used to study monthly, seasonal and annual medians of vertical eddy diffusivity, K in the troposphere, lower stratosphere and mesosphere. First, the spectral width contribution due to non-turbulent effects has been removed for further analysis and the monthly, seasonal medians of K are calculated. The monthly median of K in the troposphere shows maximum and minimum in June-July and November-December, respectively. In general, large values of K are seen up to 10 km and then decrease with height. Larger values of K are observed during monsoon and post-monsoon than in winter and summer. In general, the maximum and minimum values of the annual median of K (in logarithmic values) in the troposphere are found to be 0.25 and - 1.3 m2 s-1 respectively. In the mesosphere, the monthly median of K shows maximum and minimum during June-July and November-December, respectively, similar to the lower atmosphere. The value of K in the mesosphere becomes larger and it increases with height up to 75 km and again decreases above that height. The maximum values are seen during the summer, followed by equinoxes and a minimum during the winter. In general, the maximum and minimum values of K (in logarithmic values) are found to be 0.7 and 0.3 m2 s-1, respectively, in the mesosphere. A comparison of Doppler spectral parameters in different beam directions shows anisotropy in both signal-to- noise ratio (SNR) and spectral widths in the mesosphere, whereas it shows isotropy in SNR and anisotropy in the spectral widths in troposphere and lower stratosphere.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides)
Investigating the auroral electrojets with low altitude polar orbiting satellites
Authors: Moretto T. , Olsen N. , Ritter P. , Lu G.
Published: June 2010

Abstract. Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly in the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0.8–0.9) is observed between the amplitudes of the derived currents and the commonly used auroral electrojet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring. A specific advantage of the satellite observations over the ground-based magnetic measurements is their coverage of the Southern Hemisphere, as well as the Northern. We utilize this in an investigation of the ionospheric currents observed in both polar regions during a period of unusually steady interplanetary magnetic field with a large negative Y-component. A pronounced asymmetry is found between the currents in the two hemispheres, which indicates real inter-hemispheric differences beyond the mirror-asymmetry between hemispheres that earlier studies have revealed. The method is also applied to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning of the magnetosphere (history of the interplanetary magnetic field) is seen to play an important role, and in the winther hemisphere, it seems to be harder to drive currents on the nightside than on the dayside.Key words. Ionosphere (electric fields and currents) – Magnetospheric physics (current systems; magnetosphere-ionosphere interactions)
Modelling of geomagnetic induction in pipelines
Authors: Trichtchenko L. , Boteler D. H.
Published: June 2010

Abstract. Geomagnetic field variations induce telluric currents in pipelines, which modify the electrochemical conditions at the pipe/soil interface, possibly contributing to corrosion of the pipeline steel. Modelling of geomagnetic induction in pipelines can be accomplished by combining several techniques. Starting with geomagnetic field data, the geoelectric fields in the absence of the pipeline were calculated using the surface impedance derived from a layered-Earth conductivity model. The influence of the pipeline on the electric fields was then examined using an infinitely long cylinder (ILC) model. Pipe-to-soil potentials produced by the electric field induced in the pipeline were calculated using a distributed source transmission line (DSTL) model. The geomagnetic induction process is frequency dependent; therefore, the calculations are best performed in the frequency domain, using a Fourier transform to go from the original time domain magnetic data, and an inverse Fourier transform at the end of the process, to obtain the pipe-to-soil potential variation in the time domain. Examples of the model calculations are presented and compared to observations made on a long pipeline in the auroral zone.Key words. Geomagnetism and paleomagnetism (geo-magnetic induction)
Ion sense of polarization of the electromagnetic wave field in the electron whistler frequency band
Authors: Lundin B. , Krafft C.
Published: June 2010

Abstract. It is shown that the left-hand (or ion-type) sense of polarization can appear in the field interference pattern of two plane electron whistler waves. Moreover, it is demonstrated that the ion-type polarized wave electric fields can be accompanied by the presence at the same observation point of electron-type polarized wave magnetic fields. The registration of ion-type polarized fields with frequencies between the highest ion gyrofrequency and the electron gyrofrequency in a cold, overdense plasma is a sufficient indication for the existence of an interference wave pattern, which can typically occur near artificial or natural reflecting magnetospheric plasma regions, inside waveguides (as in helicon discharges, for example), in fields resonantly emitted by beams of charged particles or, in principle, in some self-sustained, nonlinear wave field structures. A comparison with the conventional spectral matrix data processing approach is also presented in order to facilitate the calculations of the analyzed polarization parameters.Key words. Ionosphere (wave propagation) Radio science (waves in plasma) Space plasma physics (general or miscellaneous)
Imaging radar observations and nonlocal theory of large-scale plasma waves in the equatorial electrojet
Authors: Hysell D. L. , Chau J. L.
Published: June 2010

Abstract. Large-scale (l ~ 1 km) waves in the daytime and night-time equatorial electrojet are studied using coherent scatter radar data from Jicamarca. Images of plasma irregularities within the main beam of the radar are formed using interferometry with multiple baselines. These images are analyzed according to nonlocal gradient drift instability theory and are also compared to nonlinear computer simulations carried out recently by Ronchi et al. (1991) and Hu and Bhattacharjee (1999). In the daytime, the large-scale waves assume a non-steady dynamical equilibrium state characterized by the straining and destruction of the waves by shear and diffusion followed by spontaneous regeneration as predicted by Ronchi et al. (1991). At night, when steep plasma density gradients emerge, slowly propagating large-scale vertically extended waves predominate. Eikonal analysis suggests that these waves are trapped (absolutely unstable) or are nearly trapped (convectively unstable) and are able to tunnel between altitude regions which are locally unstable. Intermediate-scale waves are mainly transient (convectively stable) but can become absolutely unstable in narrow altitude bands determined by the background density profile. These characteristics are mainly consistent with the simulations presented by Hu and Bhattacharjee (1999). A new class of large-scale primary waves is found to occur along bands that sweep westward and downward from high altitudes through the E-region at twilight.Key words. Ionosphere (equatorial ionosphere; ionospheric irregularities; plasma waves and instabilities)