bluuebunny/crossref_metadata_2025 huggingface dataset:
To reflect or not? Reflective practice in radiation therapy
Authors: Newnham John
Published: August 2006

Therapy radiographers may be empowered to contribute more freely to the multi-disciplinary professional team if they critically reflect on their inherent clinical knowledge and perspectives. Critical reflection may help radiographers articulate the rationale behind professional decisions and proposed evidence-based treatment planning and delivery protocols, and reveal knowledge embedded in practice. Documentation of professional reflection may yet become a cornerstone for continuing professional development. Despite a paucity of rigorous empirical investigation, ‘reflective practice’ has become focal in nursing education. Three concepts appear confused, ill defined or interchangeable in the literature: ‘reflective practice’, ‘reflection’ and the ‘reflective practitioner’. Debate continues into the value of ‘reflective practice’ as a system: it remains problematic, it is difficult to conceptualise, it appears to have no clear or universal definition and no certain framework or guidelines for its implementation. In reflecting on action there may be strong hindsight bias which may invalidate conclusions reached. There are doubts raised about the benefits of structured models to implement reflective practice. Belonging to such an empirically based profession, it may be that educators and clinical therapy radiographers incorporate only those elements of systematised ‘reflective practice’ that can be empirically demonstrated to be beneficial to the profession, and will result in improved patient outcomes. There is no compelling evidence yet that any systematised ‘reflective practice’ is inherently more beneficial to therapy radiographers than radiographers continuing to reflect as they do now, with or without documentation.
Information and support radiographers: a critical review of the role and its significance for the provision of cancer services
Authors: Colyer H. , Hlahla T.
Published: August 2006

The purpose of this paper is twofold; firstly, to present for wider consideration data collected about the role of information and support radiographers (ISRs) in the United Kingdom and secondly, to review critically issues of significance arising from the initial data collection and content analysis.

The empirical material is taken from a much larger survey of Oncology Centres1 whose aim was to analyse the extent and effectiveness of information and support services for cancer patients in order to evaluate service provision in a less developed country. A short, self completed postal questionnaire to identified information and support radiographers was employed. It sought to identify the main components of the ISR role, underpinning qualifications, limitations and potential for development. 64% of ISRs surveyed responded (n = 22) and the findings are presented for consideration in this paper.

The discussion comprises a critical review by the first author of some issues raised by the findings in the context of the national service framework for integrated provision2 and current developments in the practice and processes of therapeutic radiography. Specifically, the relative contribution of different aspects of the role of the ISR are evaluated, examining the benefits to patients and professionals alike. The difficulties of trailblazing a new role in a traditional, hierarchical service are explored. The necessity of a profession specific base for information and support provision in clinical oncology is questioned and it is suggested that, professionally, there are both advantages and disadvantages to this role development, but there is support for a less predatory, more interprofessional approach.
Quality control and error detection in the radiotherapy treatment process
Authors: Bate Marie-Thérèse , Speleers Bruno , Vakaet Luc A.M.L. , De Neve Wilfried J.
Published: August 2006

Purpose: In 1995, a post of quality control (QC) officer was established in the Radiotherapy Department of the University Hospital Gent (R-UZG). We report here the evolution of error detection in the domain of information transfer during the different steps of the treatment chain, in our department, since the creation of this job.

Material and Methods: From January 1995 to December 1997 (1995 n = 831; 1996: n = 1095; 1997: n = 1091), data on errors were recorded. At the start, an inventory was made of the existing situation and a Quality Assurance (QA) program was outlined for process control. According to the site of origin of errors in the treatment preparation chain, errors were separated into five levels: medical treatment prescription, simulation, treatment planning, treatment data transfer and daily set-up.

Results: The total number of errors found was 459 in 1995; 809 in 1996 and 1046 in 1997. During 1995 and 1996 the medical prescription protocols were adapted to the increasing need of the radiation technologists for more information. This explains an increased number of errors (from 80/459 to 276/809) in 1996. After a period of adaptation, the number of errors decreased in 1997 (257/1046). The second level, where many errors were found, is at the transfer phase (1995: 181/459 1996: 210/809; 1997: 336/1046). Most of these errors were made during the transfer of data from the prescription chart to the computer. These errors were due to lack of attention, human mistakes and calculation errors. The number of errors during simulation increased due to rotation of personnel in 1996. The increase persisted in 1997 for the same reason. Transfer errors due to the automatic transfer of leaf settings decreased (1995:18/29; 1996:15/17; 1997:7/31) Thanks to the start of QC management, errors were detected and corrected in the entire treatment process at R-UZG. Once changes were accepted, new challenges were initiated. After each evaluation, initiatives were taken to try to decrease specific errors. Changing attitudes was a difficult and slow process, but progress was made. The most important change in attitude certainly was the acceptation of the concept of QC.
Ultrasound guided I–125 permanent prostate implants: seed calibration and radiation exposure levels
Authors: Que William , Videla Nelson , Langer Deanna
Published: August 2006

Purpose: (1) To present data on I–125 seed calibration in a clinical setting so that reasonable tolerance levels can be set for the discrepancy in seed strength between manufacturer specified value and institution measured value; (2) To present data on measured exposure rates and estimate radiation exposure levels associated with I–125 prostate implants.

Methods and Materials: Ten percent of each batch for 50 batches of I–125 seeds were calibrated using an HDR 1000 PLUS well chamber with a single source holder. Exposure rates due to I–125 were measured by survey meters with a scintillation probe designed for low energy photon counting, as well as a survey meter of the ionization chamber type. Exposure rates of an unshielded I–125 seed, a needle loaded with three seeds, and 54 prostate implant patients immediately after the implant were obtained.

Results: Compared to the manufacturer stated midrange seed strength for a batch of seeds, the average seed strength of sampled seeds had maximum deviations of ±8%, however for 45 out of 50 batches the deviation was less than ±5%. Measured single seed strength deviated up to ±12% from the manufacturer stated midrange value, and between −11% to 7% from the mean of the sampled batch. The exposure rate of a 1.39×107 Bq (0.375 mCi) unshielded I–125 seed was about 1.548×10−8C/kgh (0.06 mR/h) at 1 m, and 1.29×10−6C/kgh (5 mR/h) at 10 cm. For a needle loaded with three seeds, the exposure rate was 1.29×10−8C/kgh (0.05 mR/h) at the handle, and 1.29×10−7C/kgh (0.5 mR/h) along the shaft. For patients implanted with I–125 seeds in the prostate, the average exposure rate was 3.61×10−8C/kgh (0.14 mR/h) at 1m, and 4.13×10−7C/kgh (1.6 mR/h) at the pelvis surface.

Conclusions: For the mean seed strength a first action level should be set at a deviation of at least 5% deviation from the manufacturer stated midrange value. For individual seeds, a first action level set at 10% deviation from the manufacturer stated midrange value seems reasonable. A person performing I–125 seed calibration or seed loading could receive up to 0.5 mSv (50 mR) per case to the hands. In the first year following an I–125 prostate implant, the spouse of the patient could receive slightly over 1mSv from the I–125 in the patient. A co-worker should not receive more than 0.5 mSv from the patient.
Towards an evidence-based 3D conformal radiotherapy prostate protocol: what is the role of spiral CT?
Authors: Newnham John
Published: August 2006

Aim: To define the role of spiral CT in evolving an evidence-based 3D Conformal Radiotherapy (CRT) prostate protocol at Lincoln, UK.

Discussion: Tumour doses traditionally prescribed at this centre to the prostate planning target volume (PTV) (64 Gy in 32 fractions) cannot be further escalated without modification of existing technique and may currently be inadequate to obtain the highest probability of local control. Prostate CRT has been demonstrated to be well tolerated with both conventional and escalated doses, however as 3D CRT PTV margins are tightened, prostate position has to be reliably predicted to avoid geographic misses or unacceptable normal tissue toxicity. The question of prostate position variability might be addressed by sequential on-treatment spiral CT scans at this centre. Spiral CT offers specific advantages of speed, small detail conspicuity, and arbitrary axial reconstruction compared to conventional CT with no attached dose penalty. Spiral CT coupled to the next generation of radiotherapy treatment planning systems (RTPs) may soon replace the CT virtual-simulator. There are significant hardware discrepancies between some present generation CT couch tops and linac couch tops. Recently published CT studies that consider prostate position variability may be fundamentally and significantly flawed due to these couch top differences. Due to a paucity of reported evidence regarding immobilisation methods, a spiral CT study is warranted to assess efficacy of immobilization method for an evidence-based prostate protocol. Confirmative spiral CT research at this centre into prostate position variability is required to select adequate margins to form the PTV for an evidence-based 3D CRT prostate protocol. Such a spiral CT study could be integrated with the immobilisation study and may separate or define the correlation (which at present is both unclear and unreported) between pelvic immobilization and prostate position variability. Initial PTV margins defined by expanding the CTV in three dimensions using an ellipsoid with major axes 1.65 times one standard deviation of prostatic displacement reported in initial studies to obtain margins of 0.7 cm laterally, 0.7 cm cranio-caudally and 1.1 cm in the AP direction are presently indicated for this centre's evidence-based prostate protocol.

Conclusion: Spiral CT will provide the essential data set for 3D CRT planning for an evidence-based prostate protocol at Lincoln. Confirmative research using spiral CT is also warranted to assess daily prostate position variability and help define the prostate PTV for an evidence based prostate protocol at this centre.
Financial implication of conformal prostate treatment
Authors: Flinton D. M. , Desai P.
Published: August 2006

Objective: The objective of this study was to directly compare the cost of conformal radiotherapy used with the RTo1 trial with that of non-conformal radiotherapy of the prostate.

Method: Two methods were employed to establish the cost, a simplistic top-down method and the more complicated bottom-up method that involved breaking down the cost elements of the respective treatments and undertaking a non-participative timing study on 37 patients undergoing radiotherapy. Costs were then ascribed based on the time the staff and equipment were utilised.

Results: The total cost of radiotherapy using the top-down method for both non-conformal radiotherapy and 32 fraction conformal radiotherapy was £2890.88, compared with £3342.58 for conformal radiotherapy using 37 fractions. The costs of the bottom-up method were £2485.67 for non-conformal radiotherapy, £2717.67 for 32 fraction conformal radiotherapy and £3110.52 for conformal radiotherapy using a 37 fraction regime.

Conclusions: Conformal radiotherapy of the prostate costs significantly more than non-conformal radiotherapy which reflects the increase in complexity of the technique. Cost differences arose due to increased time in the planning stage and in the actual treatment because of an increase in equipment and staffing costs during treatment.
Pilot study to investigate the toxicity of Aloe vera gel in the management of radiation induced skin reactions for post-operative primary breast cancer
Authors: Dudek Dana J. , Thompson Jennifer , Meegan Martina M. , Haycocks Tara R. , Barbieri Clarice , Manchul Lee A.
Published: August 2006

The purpose of this Phase 2 Breast Skin Care Pilot Study was to compare the acute skin reaction in patients undergoing radiation therapy for early breast cancer who use Aloe vera gel on the irradiated skin, with the acute skin reaction in patients from our earlier study who followed a normal skin care routine. Two secondary objectives were to assess patient compliance with the use of Aloe vera gel and the ease of using two skin toxicity scoring tools.

A total of 109 patients undergoing radiotherapy following surgery for breast cancer between October 1997 and February 1998 consented to participate in this study. Each patient applied the Aloe vera gel three times daily to the irradiated area during radiation treatment. Skin reactions were assessed objectively on a weekly basis during radiation using the Radiation Therapy Oncology Group (RTOG) and the Acute Skin Reaction Index (ASRI) skin scoring tools and subjectively by patients. All patients were followed for up to 3 weeks following treatment.

The use of Aloe vera gel did not increase the acute skin reactions due to irradiation when compared with the two arms of the previous Phase 1 Breast Skin Care Study. This pilot study demonstrated that patients could safely use Aloe vera gel while undergoing radiation therapy treatments. All patients complied uniformly with the instructions of using the gel during the study. The ASRI skin scoring tool was easier to use and more sensitive in displaying differences in skin reactions in comparison to the RTOG scale.
Physical side-effects experienced by women with breast cancer: the women's perspective
Authors: Cross Angela , Salmon Peter
Published: August 2006

Patients who receive radiotherapy need to be informed about its effects. Available evidence is inadequate because it has focused on selected symptoms and has emphasized the objective characteristics of symptoms rather than the patients' own experience of them. This study therefore examined women's own accounts of physical side-effects during the first 12 months after treatment for early breast cancer. Semi-structured audiotaped interviews with 15 patients 1 week to 12 months after treatment were analysed qualitatively. The women described some symptoms that were consistent with what is already known, in particular fatigue and skin changes, but also others that have been previously neglected. The women's explanations for symptoms were an inextricable component of their experience of them. Surprisingly, many women blamed themselves for having caused their symptoms. These findings contribute to the evidence that is necessary to inform health care professionals' advice to patients. They can also guide future quantitative research into symptoms associated with treatment and ensure that this is grounded in patients' experience of symptoms rather than clinicians' assumptions about patients' experience.
A variable shielding block for irregularly shaped megavoltage X-ray fields
Authors: Seaby A. W. , Craven C.
Published: August 2006

This technical note describes a hinged lead alloy shielding block that could be used, in certain circumstances, for shaping a megavoltage X-ray field. The construction of the shield is described and the results of transmission and penumbra measurements are given.
Sedimentation patterns, folding, and fluid upflow above a buried basement ridge: Results from 2‐D and 3‐D seismic surveys at the eastern Juan de Fuca Ridge flank
Authors: Zühlsdorff Lars , Spiess Volkhard
Published: August 2006

During R/V Sonne Cruise SO 149, new two‐dimensional (2‐D) and 3‐D multifrequency seismic data were collected at the eastern flank of the Juan de Fuca Ridge, off the west coast of North America. Two‐dimensional overview lines indicate that turbidity currents moving southward are partly trapped between a buried basement elevation called First Ridge and another elongated basement obstruction further to the west. As a consequence, sediments form a local topographic high and a distinct wedge‐shaped section in between the two ridge segments. On the basis of these seismic observations a simple conceptual model is developed to explain local sediment accumulation patterns at the flanks and on top of First Ridge. This model is consistent with seismic, coring, and drilling results that provide quantitative constraints for the remaining seafloor relief above a fully buried basement high as well as sediment porosity values on top of First Ridge that are higher than those in adjacent troughs. In general, higher porosity values may explain lower seismic reflection amplitudes, but the general trend of porosity increase above First Ridge due to vertical grain size sorting within a turbidity current has to be distinguished from additional, overprinting effects that confine the major portion of the observed reflection amplitude decrease to narrow, vertical zones. At the location of such zones, seismic data indicate that pronounced basement peaks are associated with distinct folding of the sediment layers above. It is thus suggested that the folding and the local seismic amplitude decrease are related. Folding and the associated extensional strain field forming throughout such folds can explain locally high layer inclination and increased porosity, which both affect seismic reflection amplitudes. Folding and associated fracturing may cause locally increased permeability and have the potential to focus hydrothermally driven fluid upflow and to develop the plumbing system required to explain the observed fluid seepage through a fine‐grained sediment seal.
Real contacts and evolution laws for rate and state friction
Authors: Sleep Norman H.
Published: August 2006

The well‐known formalism of rate‐ and state‐dependent friction represents the transition between static and dynamic friction. The instantaneous coefficient of friction is proportional to the logarithm of the sliding velocity V and the logarithm of a state variable ψ whose inverse is a measure of the current amount of damage within a shearing gouge layer or on a sliding surface. Evolution equations that represent the change of the state variable with time include damage from sliding and healing. The Dieterich (1979) evolution law contains separate terms for the two effects; the Ruina (1983) law groups the two effects into one term proportional to V ln(V). In addition, the state variable depends exponentially on porosity as exp[(ϕ − f)/Cɛ], where ϕ is the porosity at reference conditions and Cɛ is a dimensionless constant. I obtain these relationships as well as relationships between friction‐law parameters and physical parameters by representing asperity contacts as rectangular deformable regions between two rigid sheets. The creep rate within an asperity depends exponentially on the second invariant of the deviatoric stress . In terms of asperity‐scale quantities the invariant includes normal traction and shear traction. The derivations assume that contact stresses scale with macroscopic stresses. This yields simple expressions analogous to those in rate and state friction. The Ruina (1983) evolution law in general and the decrease in compaction rate during a hold in a slider experiment in particular arise because a sudden decrease in sliding velocity implies that the shear traction and hence the invariant decrease. The porosity‐state relationship arises when real stresses at contacts (or the inverse real contact area) depend linearly on the separation of the sheets and by analogy the porosity. Conversely, the Ruina (1983) evolution law is inapplicable when asperity‐scale stresses within a deforming material do not scale with macroscopic stresses.
Changes in daily temperature and precipitation extremes in central and south Asia
Authors: Klein Tank A. M. G. , Peterson T. C. , Quadir D. A. , Dorji S. , Zou X. , Tang H. , Santhosh K. , Joshi U. R. , Jaswal A. K. , Kolli R. K. , Sikder A. B. , Deshpande N. R. , Revadekar J. V. , Yeleuova K. , Vandasheva S. , Faleyeva M. , Gomboluudev P. , Budhathoki K. P. , Hussain A. , Afzaal M. , Chandrapala L. , Anvar H. , Amanmurad D. , Asanova V. S. , Jones P. D. , New M. G. , Spektorman T.
Published: August 2006

Changes in indices of climate extremes are studied on the basis of daily series of temperature and precipitation observations from 116 meteorological stations in central and south Asia. Averaged over all stations, the indices of temperature extremes indicate warming of both the cold tail and the warm tail of the distributions of daily minimum and maximum temperature between 1961 and 2000. For precipitation, most regional indices of wet extremes show little change in this period as a result of low spatial trend coherence with mixed positive and negative station trends. Relative to the changes in the total amounts, there is a slight indication of disproportionate changes in the precipitation extremes. Stations with near‐complete data for the longer period of 1901–2000 suggest that the recent trends in extremes of minimum temperature are consistent with long‐term trends, whereas the recent trends in extremes of maximum temperature are part of multidecadal climate variability.
Variable resolution general circulation models: Stretched‐grid model intercomparison project (SGMIP)
Authors: Fox‐Rabinovitz Michael , Côté Jean , Dugas Bernard , Déqué Michel , McGregor John L.
Published: August 2006

Variable resolution general circulation models (GCMs) using a global stretched grid with enhanced uniform resolution over the region(s) of interest have proven to be an established approach to regional climate modeling providing an efficient regional downscaling to mesoscales. This approach has been used since the early to mid‐1990s by climate modeling groups from France, the United States, Canada, and Australia, among others, along with or as an alternative to the current widely used nested‐grid approach. Stretched‐grid GCMs are used for continuous/autonomous climate simulations, as are usual GCMs, with the only difference being that variable resolution grids are used instead of more traditional uniform grids. The important advantages of variable resolution stretched‐grid GCMs are that they do not require any lateral boundary conditions/forcing and are free of the associated undesirable computational problems; as a result, they provide self‐consistent interactions between global and regional scales of motion and their associated phenomena as in uniform grid GCMs. The international stretched‐grid model intercomparison project, phase 1 (SGMIP‐1), using variable resolution GCMs developed at major centers/groups in Australia, Canada, France, and the United States, was initiated in 2001 and successfully conducted in 2002–2005. The results of the 12‐year (1987–1998) climate simulations for a major part of North America are available at the SGMIP Web site: http://essic.umd.edu/∼foxrab/sgmip.html. The SGMIP‐1 multimodel ensemble results for the region compare well with reanalysis and observations in terms of spatial and temporal diagnostics. Regional biases for time‐averaged model products are mostly limited to about half (or less) of typical reanalysis errors, i.e., within the uncertainties of the available reanalyses, while a high quality of global circulation is preserved. SGMIP products are available to national and international programs such as the World Meteorological Organization/World Climate Research Program/Working Group on Numerical Experimentation (WMO/WCRP/WGNE).
Inverse modeling of the global methyl chloride sources
Authors: Yoshida Yasuko , Wang Yuhang , Shim Changsub , Cunnold Derek , Blake Donald R. , Dutton Geoffrey S.
Published: August 2006

Inverse modeling using the Bayesian least squares method is applied to better constrain the sources and sinks of atmospheric methyl chloride (CH3Cl) using observations from seven surface stations and eight aircraft field experiments. We use a three‐dimensional global chemical transport model, the GEOS‐Chem, as the forward model. Up to 39 parameters describing the continental/hemispheric and seasonal dependence of the major sources of CH3Cl are used in the inversion. We find that the available surface and aircraft observations cannot constrain all the parameters, resulting in relatively large uncertainties in the inversion results. By examining the degrees of freedom in the inversion Jacobian matrix, we choose a reduced set of parameters that can be constrained by the observations while providing valuable information on the sources and sinks. In particular, we resolve the seasonal dependence of the biogenic and biomass‐burning sources for each hemisphere. The in situ aircraft measurements are found to provide better constraints on the emission sources than surface measurements. The a posteriori emissions result in better agreement with the observations, particularly at southern high latitudes. The a posteriori biogenic and biomass‐burning sources decrease by 13 and 11% to 2500 and 545 Gg yr−1, respectively, while the a posteriori net ocean source increases by about a factor of 2 to 761 Gg yr−1. The decrease in biomass‐burning emissions is largely due to the reduction in the emissions in seasons other than spring in the Northern Hemisphere. The inversion results indicate that the biogenic source has a clear winter minimum in both hemispheres, likely reflecting the decrease of biogenic activity during that season.
Laboratory studies of ice formation via deposition mode nucleation onto mineral dust and n‐hexane soot samples
Authors: Kanji Zamin A. , Abbatt Jonathan P. D.
Published: August 2006

Laboratory studies are described whereby the heterogeneous ice nucleating ability of various dust samples was studied for particles mounted on a hydrophobic cold stage. Ice formation is observed using digital photography. The relative humidity with respect to ice (RHi) and temperature conditions of the flow system are validated by observing (NH4)2SO4 deliquescence. Four types of solid mineral samples, including authentic Saharan dust and commercial samples of alumina, silica, and montmorillonite, were investigated in the deposition freezing mode. The size of the dust particles ranged from 0.5 to 5 μm, and the temperature range was from 263 to 218 K. With roughly 104 particles present on the cold stage, the onset for ice formation was observed at low RHs, between 102 and 108% RHi, for all samples and temperatures. This indicates that deposition mode nucleation is an efficient mode of ice formation, particularly under the cold temperatures prevalent in the cirrus regime. By contrast, ice deposition onto n‐hexane soot particles was not nearly so efficient. Nucleation rates are calculated as a function of RHi from experiments conducted with Saharan dust, where we measured the dependence of the onset RHi on total dust surface area.
Impact constraints on, and a chronology for, major events in early Mars history
Authors: Frey H. V.
Published: August 2006

Large‐diameter visible and buried impact basins, seen as “quasi‐circular depressions” (QCDs) in MOLA gridded data, provide a self‐consistent chronology for major events on early Mars in terms of N(200) crater retention ages. On the basis of a conversion to model absolute ages, this chronology extends back hundreds of millions of years into a previously unknown “pre‐Noachian” epoch during which a now buried highlands surface was established, in which several very large impact basins formed while the global magnetic field was still present. A cluster of very large “lowland‐making” basins occurred at a model age of about 4.13 GY (or earlier), forming the fundamental topography of the Mars crustal dichotomy at a time prior to the age of the oldest visible highland crust. This early event in Martian history marks the transition from the “pre‐Noachian” to the Early Noachian when the well‐preserved Hellas, Argyre, and Isidis basins formed, all after the global magnetic field died.
No major deglaciation across the Miocene‐Pliocene boundary: Integrated stratigraphy and astronomical tuning of the Loulja sections (Bou Regreg area, NW Morocco)
Authors: van der Laan E. , Snel E. , de Kaenel E. , Hilgen F. J. , Krijgsman W.
Published: August 2006

An integrated high‐resolution stratigraphy and orbital tuning is presented for the Loulja sections located in the Bou Regreg area on the Atlantic side of Morocco. The sections constitute the upward continuation of the upper Messinian Ain el Beida section and contain a well‐exposed, continuous record of the interval straddling the Miocene‐Pliocene (M‐P) boundary. The older Loulja‐A section, which covers the interval from ~5.59 to 5.12 Ma, reveals a dominantly precession‐controlled color cyclicity that allows for a straightforward orbital tuning of the boundary interval and for detailed cyclostratigraphic correlations to the Mediterranean; the high‐resolution and high‐quality benthic isotope record allows us to trace the dominantly obliquity‐controlled glacial history. Our results reveal that the M‐P boundary coincides with a minor, partly precession‐related shift to lighter “interglacial” values in d18O. This shift and hence the M‐P boundary may not correlate with isotope stage TG5, as previously thought, but with an extra (weak) obliquity‐controlled cycle between TG7 and TG5. Consequently, the M‐P boundary and basal Pliocene flooding of the Mediterranean following the Messinian salinity crisis are not associated with a major deglaciation and glacio‐eustatic sea level rise, indicating that other factors, such as tectonics, must have played a fundamental role. On the other hand, the onset of the Upper Evaporites in the Mediterranean marked by hyposaline conditions coincides with the major deglaciation step between marine isotope stage TG12 and TG11, suggesting that the associated sea level rise is at least partly responsible for the apparent onset of intermittently restricted marine conditions following the main desiccation phase. Finally, the Loulja‐A section would represent an excellent auxiliary boundary stratotype for the M‐P boundary as formally defined at the base of the Trubi marls in the Eraclea Minoa section on Sicily.
Relationship between geochemical parameters and the occurrence of Dehalococcoides DNA in contaminated aquifers
Authors: Lu Xiaoxia , Wilson John T. , Kampbell Donald H.
Published: August 2006

Strains of Dehalococcoides are the only microbes known that can completely dechlorinate PCE, TCE, cis‐DCE, and vinyl chloride to ethylene. Either naturally occurring strains or bioaugmentation cultures of Dehalococcoides are widely used for in situ bioremediation of contaminated groundwater. Naturally occurring strains have an important role in natural attenuation of PCE, TCE, cis‐DCE, and vinyl chloride in groundwater. This study evaluated the relationship between selected biogeochemical parameters and the presence of Dehalococcoides DNA in field‐scale plumes. A total of 81 monitoring wells were sampled from 15 groundwater plumes at 10 locations across the United States (one sample per monitoring well). The presence of Dehalococcoides DNA was determined with an assay based on the polymerase chain reaction (PCR) using DNA primers targeting the 16S rRNA gene of Dehalococcoides. The groundwater samples were also analyzed for concentrations of O2, NO3−1 plus NO2−1 − N, CH4, H2, Fe (II), SO4−2, TOC, Cl−1, and benzene, toluene, ethylbenzene, and xylene (BTEX) compounds and for alkalinity, ORP, electrical conductivity, pH, and temperature. Dehalococcoides DNA was unequivocally detected in 26 wells, most of which exhibited methanogenic conditions. A two‐sample Kolmogorov‐Smirnov test was used to compare the distribution of each parameter in water where Dehalococcoides DNA was present to the distribution where Dehalococcoides DNA was absent. The only parameters for which the distributions were different at 95% confidence were NO3−1 plus NO2−1 − N, CH4, and ORP. Using these three statistically significant geochemical parameters as descriptors, a predictive model for the presence of Dehalococcoides DNA was developed using logistic regression with a binary response. Under conditions where data of direct biochemical assay are not available a calculated probability could be used to properly calibrate computer models of natural attenuation.
Clean two‐ and three‐dimensional analytical solutions of Richards' equation for testing numerical solvers
Authors: Tracy F. T.
Published: August 2006

This technical note derives clean analytical solutions of Richards' equation for three‐dimensional unsaturated groundwater flow. Clean means that the boundary conditions and steady state solutions are closed form expressions and the transient solutions have relatively simple additional Fourier series terms. Two‐dimensional versions of these solutions are also given. The primary purpose for the solutions is to test linear and nonlinear solvers in finite difference/volume/element computer programs for accuracy and scalability using architectures ranging from PCs to parallel high‐performance computers. This derivation starts from the quasi‐linear assumption of relative hydraulic conductivity varying exponentially with pressure head and the separate approximation that relative hydraulic conductivity varies linearly with moisture content. This allows a transformation to be used to create a linear partial differential equation. Separation of variables and Fourier series are then used to obtain the final solution. Physically reasonable material properties are also used. A total of four solutions are given in this technical note (steady state and transient solutions for two different boundary conditions of the sample problem).
EOS MLS observations of dehydration in the 2004–2005 polar winters
Authors: Jiménez C. , Pumphrey H. C. , MacKenzie I. A. , Manney G. L. , Santee M. L. , Schwartz M. J. , Harwood R. S. , Waters J. W.
Published: August 2006

Observations of water vapour and temperature from the Earth Observing System Microwave Limb Sounder are used to study dehydration in the 2004 and 2005 polar vortices. Significant differences were found for the Antarctic winters, with the 2005 vortex colder and more extensively dehydrated. For the 2005 winter water vapour reductions were observed from mid‐June, coincident with a decrease in temperatures, extending vertically between ∼12–21 km. Reductions of up to ∼3 ppmv in water vapour were recorded a month later. Permanent dehydration was apparent between ∼15–20 km, where 3 months later the temperature recovery was not followed by a recovery in water vapour. The 2004–2005 Arctic winter was unusually cold, but only one single event of depleted water vapour at the end of January was linked to ice formation. For this event, a reduction of up to ∼0.5 ppmv was observed over Spitsbergen between ∼12–20 km.
Simultaneous global observations of glyoxal and formaldehyde from space
Authors: Wittrock Folkard , Richter Andreas , Oetjen Hilke , Burrows John P. , Kanakidou Maria , Myriokefalitakis Stelios , Volkamer Rainer , Beirle Steffen , Platt Ulrich , Wagner Thomas
Published: August 2006

The first global simultaneous observations of glyoxal (CHOCHO) and formaldehyde (HCHO) columns retrieved from measurements by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) satellite instrument are presented and compared to model calculations. The global pattern of the distribution of CHOCHO is similar to that of HCHO. High values are observed over areas with large biogenic isoprene emissions (Central Africa, parts of South America, and Indonesia). Also regions with biomass burning and anthropogenic pollution exhibit elevated levels of CHOCHO. The ratio of the columns of CHOCHO to HCHO is generally of the order of 0.05 in regions having biogenic emissions, which is in reasonable agreement with the current understanding of the oxidation of hydrocarbons emitted by the biosphere. However and in contrast to our model, high values of both HCHO and CHOCHO are also observed over areas of the tropical oceans. This is tentatively attributed to outflow from the continents and local oceanic biogenic sources of the precursors of HCHO and CHOCHO.
Dynamic feedbacks of troposphere aerosols on marine low cloud during boreal spring
Authors: Kim Maeng‐Ki , Lee Woo‐Seop
Published: August 2006

The effects of troposphere aerosols on marine low cloud during boreal spring are investigated using the NASA finite‐volume general circulation model with Microphysics of clouds in Relaxed Arakawa Schubert Scheme. This study shows that the marine low cloud can be modified by two types of regimes over North Pacific Ocean. In regime I, the North Pacific High (NPH) intensified by aerosol direct effects induces an increase in lower‐tropospheric static stability and, hence, marine low cloud through strong inversion by adiabatic warming. In regime II, intensified NPH induces an increase of surface evaporation off the west coast of California through strong surface wind, increasing marine low cloud through the supply of moisture at sea surface and local moisture convergence. These results mean that the radiative effect due to the feedback of low cloud amounts appear to be stronger than that of the aerosol direct effect in itself.
Seasonal and interannual variability of calcite in the vicinity of the Patagonian shelf break (38°S–52°S)
Authors: Signorini Sergio R. , Garcia Virginia M. T. , Piola Alberto R. , Garcia Carlos A. E. , Mata Mauricio M. , McClain Charles R.
Published: August 2006

The timing and duration of coccolithophore blooms along the Patagonian shelf break, as well as insights on the mechanisms that drive and maintain these blooms, were analyzed using time series of chlorophyll chl a, calcite, and sea‐surface temperature (SST) derived from remote sensing data (SeaWiFS and AVHRR) and historic hydrographic data. The seasonal variability and succession of phytoplankton groups respond to light intensity and nutrient supply within the mixed layer due to seasonal changes in stratification. The early spring bloom is diatom‐dominated and starts in September under nutrient‐rich Malvinas waters when the mixed layer begins to shallow (<80 m), and peaks around November with mixed layer depths (MLD) less than 40 m. After nutrient depletion from the spring bloom, a coccolithophore bloom begins in November when the MLD is less than 40 m, and peaks in January when the MLD reaches its minimum (18 m) and PAR reaches its maximum intensity.
Statistical modeling of storm‐level Kp occurrences
Authors: Remick K. J. , Love J. J.
Published: August 2006

We consider the statistical modeling of the occurrence in time of large Kp magnetic storms as a Poisson process, testing whether or not relatively rare, large Kp events can be considered to arise from a stochastic, sequential, and memoryless process. For a Poisson process, the wait times between successive events occur statistically with an exponential density function. Fitting an exponential function to the durations between successive large Kp events forms the basis of our analysis. Defining these wait times by calculating the differences between times when Kp exceeds a certain value, such as Kp ≥ 5, we find the wait‐time distribution is not exponential. Because large storms often have several periods with large Kp values, their occurrence in time is not memoryless; short duration wait times are not independent of each other and are often clumped together in time. If we remove same‐storm large Kp occurrences, the resulting wait times are very nearly exponentially distributed and the storm arrival process can be characterized as Poisson. Fittings are performed on wait time data for Kp ≥ 5, 6, 7, and 8. The mean wait times between storms exceeding such Kp thresholds are 7.12, 16.55, 42.22, and 121.40 days respectively.
Anomalous low‐velocity zone and linear alignment of seismicity along it in the subducted Pacific slab beneath Kanto, Japan: Reactivation of subducted fracture zone?
Authors: Nakajima Junichi , Hasegawa Akira
Published: August 2006

A detailed investigation of the hypocenter distribution beneath Kanto, Japan, reveals a NW‐SE‐trending linear alignment of seismicity within the subducted Pacific slab. We estimate the 3D seismic velocity structure in the Pacific slab to understand the factors controlling the genesis of such intraslab earthquakes. A narrow low‐velocity zone is imaged within the subducted slab over a length of ∼150 km, which partly penetrates into the mantle portion of the slab. The low‐velocity zone correlates in space with the NW‐SE‐trending earthquake cluster. A reactivation of hydrated fracture zone formed prior to subduction is probably related to the low‐velocity anomaly. Dehydration reactions of the hydrated oceanic mantle as well as the oceanic crust might lower the seismic velocity along the fossil fracture zone, accompanied by intraslab earthquakes. These observations support the hypothesis of dehydration embrittlement as the most viable mechanism for generating intraslab earthquakes.
Measuring two‐dimensional movements using a single InSAR pair
Authors: Bechor Noa B. D. , Zebker Howard A.
Published: August 2006

We present a new method to extract along‐track displacements from InSAR data, based on split‐beam InSAR processing, to create forward‐ and backward‐looking interferograms. The phase difference between the two modified interferograms provides the along‐track displacement component. Thus, from each conventional InSAR pair we extract two components of the displacement vector: one along the line of sight, the other in the along‐track direction. We analyze the precision of the new method by comparing our solution to GPS and offset‐derived along‐track displacements in interferograms of the 1999, Hector Mine earthquake. The RMS error between GPS displacements and our results ranges from 5 to 8.8cm. Our method is consistent with along‐track displacements derived by pixel‐offsets, which are limited to 12–15cm precision. The theoretical precision of the new method depends on SNR and coherence. For a signal to noise ratio of 30 the expected precisions are 3, 11cm for coherence of 0.8, 0.4, respectively.
Interannual change in summertime precipitation over northeast Asia
Authors: Iwao Koki , Takahashi Masaaki
Published: August 2006

The summertime precipitation over northeast Asia (Mongolia and Inner Mongolia) increased from 1980 to the mid‐1990s, and low‐precipitation summers continued for 4 years from 1999. A vegetation index based on satellite observations shows a similar interannual change. The first EOF mode of the interannual change of July precipitation shows a seesaw pattern between northeast Asia and Siberia, and the time coefficient represents the summertime precipitation change over northeast Asia. This mode is associated with Rossby waves propagating eastward over the Eurasian continent, which accompany anomalous meridional winds over northeast Asia and Siberia, resulting in anomalous vertical flows. The vertical flows over these regions are connected with each other through the meridional circulation, which contributes to form the seesaw pattern by suppressing or enhancing the precipitation.
Titan's planetary boundary layer structure at the Huygens landing site
Authors: Tokano Tetsuya , Ferri Francesca , Colombatti Giacomo , Mäkinen Teemu , Fulchignoni Marcello
Published: August 2006

Huygens Atmospheric Structure Instrument (HASI) for the first time performed an in situ measurement of the thermal structure in Titan's atmosphere with a vertical resolution sufficient to analyze the planetary boundary layer (PBL). The vertical potential temperature profile reveals the presence of a weakly convective PBL, with a surface layer thickness of 10 m and an outer layer with a depth of 300 m. With a mean eddy diffusivity of only ∼7.4 × 10−3 m2 s−1, the turbulence in the PBL is weak. The turbulent heat flux in the surface layer was upward but tiny (∼0.02 W m−2), indicating that the ground surface was marginally warmer than the air. The surface heat flux is too small to cause a diurnal variation of the PBL except in the lowest few meters, so the observed profile may be a nearly steady state feature within this season at the landing site. In the surface layer the mean wind speed is likely to be less than 0.1 m s−1. Given the tiny surface heat flux, the buoyant production of turbulence is very weak. The PBL structure reveals that the weather condition at the time and place of the Huygens landing resembles a calm, overcast day on Earth but is clearly different from the PBL typical for the polar night.
Selection and characterization of an HIV‐1 gp120‐binding affibody ligand
Authors: Wikman Maria , Rowcliffe Eric , Friedman Mikaela , Henning Petra , Lindholm Leif , Olofsson Sigvard , Ståhl Stefan
Published: August 2006

To evaluate the possibility of generating novel proteins binding to highly glycosylated viral proteins, affibody ligands were selected by bacteriophage display technology to the HIV‐1 envelope glycoprotein gp120 (glycoprotein 120), from a combinatorial protein library based on the 58‐amino‐acid‐residue staphylococcal Protein A domain. The predominant variant from the bacteriophage selection was produced in Escherichia coli and characterized by biosensor analyses. Both univalent and bivalent affibody molecules were shown to bind selectively to the gp120 target molecule in a biosensor analysis. The dissociation equilibrium constants (KD) were determined to be approx. 100 nM for the univalent affibody and 10 nM for the bivalent affibody, confirming the stronger gp120 binding of the bivalent affibody ligand. The affibody constructs were further introduced into the Ad5 (adenovirus type 5) fibre gene, and the recombinant fibres were shown to bind selectively to gp120 in a biosensor analysis and to gp160 transiently expressed in African‐green‐monkey (Cercopithecus aethiops) kidney cells. Neither the affibody ligand nor the Ad5 fibres showed any virus neutralization activity, suggesting that the affibody bound to a non‐neutralizing site on gp120. To investigate the binding site for the affibody ligand on gp120, CD4 (cluster of differentiation 4) and a panel of mAbs (monoclonal antibodies) known to bind to gp120 were allowed to compete with the affibody ligand in a biosensor study. Two mAbs, 670‐30D and 697‐30D, were found to compete with gp120 for overlapping binding sites. Although neutralization effects were not achieved in this initial investigation, the successful selection of a gp120‐binding affibody ligand indicates that future affibody‐based strategies might evolve to complement antibody‐based efforts for HIV‐1 therapy. Strategies for directed selection of affibody ligands binding to neutralizing epitopes and the potential of using adenovirus for gene‐therapy‐mediated efforts are discussed.