bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Definition of Genetic Counseling: National Society of Genetic Counselors’ Task Force Report
Authors: Resta Robert , Biesecker Barbara Bowles , Bennett Robin L. , Blum Sandra , Estabrooks Hahn Susan , Strecker Michelle N. , Williams Janet L.
Published: May 2006

The Genetic Counseling Definition Task Force of the National Society of Genetic Counselors (NSGC) developed the following definition of genetic counseling that was approved by the NSGC Board of Directors:

Genetic counseling is the process of helping people understand and adapt to the medical, psychological and familial implications of genetic contributions to disease. This process integrates the following:

•Interpretation of family and medical histories to assess the chance of disease occurrence or recurrence.

•Education about inheritance, testing, management, prevention, resources and research.

•Counseling to promote informed choices and adaptation to the risk or condition.

The definition was approved after a peer review process with input from the NSGC membership, genetic professional organizations, the NSGC legal counsel, and leaders of several national genetic advocacy groups.
Prominence in Tamil
Authors: Keane Elinor
Published: May 2006

This paper investigates whether or not there are phonetic correlates of prominence at the word level in Tamil that can be associated with word-initial stress. There is no lexically distinctive stress but there are indications in previous work – based on impressionistic judgements and experimental evidence of vowel reduction patterns – that word-initial syllables may be prominent. Sets of words containing segmentally identical syllables in different positions within the word, e.g. [nariku], [kanavu] and [w o:dina] were recorded by five speakers in a carrier phrase. The prosodic properties of the test syllables were compared to establish whether syllable position had a significant effect. No consistent results were found for either duration or loudness: their role at the word level in Tamil seems to be confined to marking intrinsic segmental and quantitative distinctions. Significant differences in F0 related to syllable position would be consistent with initial syllables bearing abstract word-level prominence. This would be marked primarily through the association of phrasal pitch accents, unaccompanied by independent differences of loudness or robust durational effects.
The effect of pitch span on intonational plateaux
Authors: Knight Rachael-Anne , Nolan Francis
Published: May 2006

Previous research has indicated that the H (high) of a nuclear accent may be realized as a flat stretch of contour rather than as a single turning point. Both the duration of this plateau and its alignment within the accented syllable are affected by the segmental and prosodic structure of the utterance. The present work investigates whether a non-structural variable, namely pitch span, also affects the realization of the plateau. Speakers replicated all-sonorant utterances in different pitch spans. Results show that both the duration and alignment of the plateau vary with pitch span but in ways different from the way they vary with prosodic structure. Importantly, results also indicate that, when using a proportional measure of alignment, the end of the plateau is anchored within the syllable for each speaker and may be a marker of linguistic structure.
Vocalic context as a condition for nasal coda emergence: aerodynamic evidence
Authors: Shosted Ryan K.
Published: May 2006

Nasal coda emergence (NCE) (sometimes referred to as ‘restoration’) is the process by which a nasal vowel develops an excrescent nasal coda which may or may not have been present in an earlier form of the spoken language. NCE is operative in the Carioca (Rio de Janeiro) dialect of Brazilian Portuguese (CBP), an Ibero-Romance language with five phonemically nasal vowels. The output of NCE (in this language) is usually a velar nasal. It has been suggested that the process may be a function of tongue position (Hajek 1991: 262). To test the null hypothesis that NCE does not correlate with vowel height or anteriority, aerodynamic (nasal and oral flow) signals were obtained from three speakers of CBP. The speakers uttered words ending in nasal vowels while wearing a circumferentially-vented pneumotach split-flow air mask. For comparative purposes, parallel data were gathered from a Hindi and a French speaker as well. The maximum nasal percentage of total flow and the maximum real nasal flow (in ml/s) were measured for each token, averaged across vowels and, in the case of CBP, across speakers. For CBP, the null hypothesis is rejected, lending support to the alternative: vowel height and posteriority indeed condition the emergence of NCE. This suggests a role for the lowered velum and/or raised tongue body in the development of coda obstruents on nasal vowels.
Non-durational indices in Italian geminate consonants
Authors: Payne Elinor M.
Published: May 2006

This paper presents the results of an electropalatographic investigation into non-durational properties of Italian consonant gemination. The evidence suggests a more palatalised tongue configuration during the production of geminate coronal sonorants and stops than in their non-geminate counterparts. Evidence is also found of differences in the active articulator, with a laminal articulation more characteristic of geminates, and an apical articulation of non-geminates. It is proposed that Italian gemination be thought of more broadly as fortition, and the implications of this are discussed.
Gayo
Authors: Eades Domenyk , Hajek John
Published: May 2006

Gayo is an Austronesian language spoken by some 260,000 people in the central highlands of the Indonesian province of Aceh, at the northern tip of the island of Sumatra. Gayo belongs to the Malayo-Polynesian branch of the Austronesian family of languages (Ross 1995, Blust 1999). Nothofer (1994) places Gayo along with Nias, Mentawai, Enggano and the various Batak languages in a North-West Sumatra/Barrier Islands subgroup. Five distinct but mutually intelligible dialects are recognised within Gayo: Bukit, Dëret, Cik, Serbejadi and Lues.
The dialect of Hasselt
Authors: Peters Jörg
Published: May 2006

Hasselt is the capital of the Belgian province of Limburg, with a population of some 68,000. The town is situated in the northern part of Belgium, about 35 km west of the national border between Belgium and the Netherlands, and 20 km north of the Dutch-French language border, which separates Belgium into a northern part (Flanders) and a southern part (Wallonia). The dialect of Hasselt belongs to the West-Limburgian dialect group (Goossens 1965). The number of dialect speakers is steadily diminishing, and the remaining ones are all bilingual with Standard Belgian Dutch (cf. Verhoeven 2005). An early comprehensive description of this dialect is given by Grootaers & Grauls (1930). The only available dictionary is Staelens (1989).
The peg view made easy – an adjunct to a current clinical protocol
Authors: Hamilton S. E. , Yielder P. , Yielder J.
Published: May 2006

Purpose: In 2001 an evaluative study was conducted involving an oral positioning aid (the E-Z-Em Mouthpiece). Manufacturer opinion suggested that the device may enhance safe and demonstrative practice in the radiographic and radiological components of case examinations involving acute trauma to the upper cervical spine. The study was conducted at Auckland Public and Starship Children's Hospitals, New Zealand with prior approval from Auckland Health Research Human Subjects Ethics Committee.

Literature review confirms that the atlanto-axial compartment of the cervical spine is most commonly involved in acute cervical spine injury. Consequently difficulty experienced in achieving adequate and optimal radiographic demonstration of the osseous and articular structures of this complex region is well reported.

Methods: The study adopted applied programme evaluation – methodology. The evaluation was conducted within a time frame stipulated by the ethics approval. All participating subjects presented with a case history of trauma to the cervical spine referred for initial radiological assessment from either accident and emergency or admission departments. Radiographers who performed the examinations were requested to use the positioning device. When the examination was concluded, questionnaire participation was requested to provide reports from each examination. These reports were then subjected to analysis.

Results: Seventy-five patients participated in the study. Thirty-three questionnaires were completed (a respondent rate of 44%). Responses tended to endorse provision of the device for optional use within current examination practice. Factors influencing optional use of the device were difficulties associated with subject type, the position of external immobilising collars, peripheral injuries sustained by the patient and difficulty experienced with those subjects who had suffered multiple injuries with associated head injury.

Conclusions: This study supports provision for the availability and optional use of this product in certain cases, supporting the manufacturer's assessment of its capability to enhance aspects of image quality and assist subject immobilisation.
The X-ray request – an effective vehicle of communication?
Authors: Longrigg B. A. , Channon B. T.
Published: May 2006

An X-ray request is an essential vehicle for communicating clinical information from the referring clinician to the radiographer, responsible for undertaking the procedure, who requires sufficient information to justify an exposure. Abbreviations and illegible handwriting can reduce this expected level of communication. Abbreviations were included on 81% of the request forms audited in this study and 9% of request forms were considered to be illegible. Radiographers have a high acceptance level of abbreviations compared to illegible handwriting. This study demonstrated that abbreviations could have more than one meaning to individual radiographers. Thus radiographers could waste valuable clinical time locating the referring clinician to clarify the implied meaning. The incorrect interpretation of the meaning of an abbreviation could lead to an erroneous examination being undertaken with subsequent medico-legal implications.
Intramuscular spindle cell lipoma of the sternomastoid muscle – imaging and pathological appearances
Authors: Williams M. D. , Howlett D. C. , Violaris N. , Ramesar K.
Published: May 2006

Spindle cell lipoma (SCL) is a rare neoplasm occurring predominantly in male patients between the ages of 45 and 70 years. We present a case of SCL arising in the sternomastoid muscle of a 46 year old male patient, which was completely excised at surgery. (Only 4 cases of SCL have been described within skeletal muscle and SCL has not previously been reported within sternomastoid.) The histological and magnetic resonance (MR) imaging features of this lesion are described and the differential diagnosis is discussed, with particular reference to its potential confusion with liposarcoma.
The upper limb radiographs in accident and emergency departments: red dotting and pattern recognition – a survival guide
Authors: Hughes K.
Published: May 2006

The upper limb radiograph is an extremely common request with trauma. The practising radiographer requires familiarity with normal and abnormal appearances. Recognition of fractures and dislocations is essential and illustrated in this article. This is especially so with the difficult paediatric elbow and suggestions are given for recognising fractures and often subtle dislocations such as the dislocated internal epicondyle. Lines of assessment at the elbow and the value of the elbow fat pad are highlighted.
A closed form solution for constant flux pumping in a well under partial penetration condition
Authors: Yang Shaw‐Yang , Yeh Hund‐Der , Chiu Pin‐Yuan
Published: May 2006

An analytical model for the constant flux pumping test is developed in a radial confined aquifer system with a partially penetrating well. The Laplace domain solution is derived by the application of the Laplace transforms with respect to time and the finite Fourier cosine transforms with respect to the vertical coordinates. A time domain solution is obtained using the inverse Laplace transforms, convolution theorem, and Bromwich integral method. The effect of partial penetration is apparent if the test well is completed with a short screen. An aquifer thickness 100 times larger than the screen length of the well can be considered as infinite. This solution can be used to investigate the effects of screen length and location on the drawdown distribution in a radial confined aquifer system and to produce type curves for the estimation of aquifer parameters with field pumping drawdown data.
A case study of mesospheric gravity wave momentum flux and dynamical instability using the Arecibo dual beam incoherent scatter radar
Authors: Zhou Qihou , Morton Y. T.
Published: May 2006

We report the first observation of gravity wave momentum flux in the mesosphere using the dual‐beam Arecibo incoherent scatter radar (ISR). Quasi‐monochromatic waves were observed throughout the daytime of July 28, 2001 in the altitude range of 65–85 km. The largest wave speed was about 100 m/s and the dominant period was about 15 min. Instability, as indicated by the Richardson number, occurred at several altitudes, most dramatically at 77 and 81 kilometers. The zonal momentum flux is found to change sign at altitudes where dynamical instability occurs. No significant gravity waves were observed in the region having an eastward background wind, while they were ubiquitous when the background wind was westward.
Relationship between satellite‐observed cold water along the Primorye coast and sea ice in the East Sea (the Sea of Japan)
Authors: Park Kyung‐Ae , Kim Kuh , Cornillon Peter C. , Chung Jong Yul
Published: May 2006

The relationship between cold surface water along the Primorye coast and sea ice in the Tatar Strait of the northern East Sea (the Sea of Japan) is examined by analyzing sea surface temperatures (SST) from NOAA/AVHRR, sea ice concentrations from SSM/I, wind vectors from QuikSCAT, and position data from satellite‐tracked drifting buoys. Relatively low SSTs along the Primorye coast in spring and early summer are attributed to sea ice melted water advected to the southwest as the Liman Cold Current (LCC). Monthly to year‐to‐year variations of SSTs along the Primorye coast in spring and early summer are negatively correlated with those of the sea ice concentration in the Tatar Strait during the previous winter. Translational speeds from the surface drifter and SST anomalies demonstrate that the LCC significantly varies by 2–18 km/day both in space and time.
Aspects of alluvial fan shape indicative of formation process: A case study in southwestern California with application to Mojave Crater fans on Mars
Authors: Williams Rebecca M. E. , Zimbelman James R. , Johnston Andrew K.
Published: May 2006

Longitudinal profiles from six alluvial fans surveyed in southwestern California have quantitative attributes that can distinguish formation processes. The radial slope of fans where debris flow processes dominated is constant while fluvially‐fed fans have a concave‐upward shape. We find the power law regression of upstream slope‐distance profiles is the preferred approach for assessing concavity. Concavity index, the exponential determined via power law regression analysis, is an accurate reflection of the magnitude of the concavity and thus a qualitative measure of the relative influence of fluvial processes on the fan. Fan length and surface gradient are inversely correlated: debris flow fans are shorter and steeper (>15°) than their fluvial counterparts. The results of this investigation provide criteria to evaluate hypothesized formation processes and provide constraints on the amount of fluid and timescales involved in the generation of comparably‐sized fans within Mojave Crater, Mars.
Magnetospheric transmission function approach to disentangle primary from secondary cosmic ray fluxes in the penumbra region
Authors: Bobik P. , Boella G. , Boschini M. J. , Gervasi M. , Grandi D. , Kudela K. , Pensotti S. , Rancoita P. G.
Published: May 2006

The AMS‐01 observations (in June 1998, on board the space shuttle orbiter Discovery) have shown the presence of primary (PCR) and secondary (SCR) cosmic rays (most of them protons) at a low Earth orbit (about 400 km altitude). The SCRs are mostly created in interactions with the atmosphere by fast PCRs and can be trapped or become reentrant albedo particles. Some of them seem to be sufficiently energetic to populate the “penumbra region” above the local geomagnetic cutoff rigidity. A backtracking procedure of simulated protons entering the AMS‐01 spectrometer has provided the fraction of allowed (and hence forbidden) trajectories of PCRs. Consequently, it has allowed the determination of the so‐called transmission function (TF) which is able to describe the properties of the PCR transport from the Earth's magnetopause (i.e., the primary spectrum at 1 AU) to the atmosphere and finally the fluxes of the PCRs in the ten geomagnetic regions for AMS‐01 observations. In the penumbra regions, the observed spectra of the AMS‐01 geomagnetic regions have been found to be larger than those predicted for the PCRs in the penumbra region by means of the TF, i.e., some SCRs (mainly reentrant albedo protons) are also found to populate the rigidity regions above the local geomagnetic cutoff rigidity. The fraction of the secondary to overall particle flux in the penumbra region increases gradually as the geomagnetic latitude increases.
Electromagnetic waves downstream of quasi‐perpendicular shocks
Authors: Lu Q. M. , Wang S.
Published: May 2006

When the incident solar wind H+ and other minor ions cross a shock, they are decelerated differentially by the electrostatic potential at the shock. Therefore ring beam distributions of the minor ions are formed downstream of a quasi‐perpendicular shock in the downstream frame. Moreover, the H+ distribution downstream of the quasi‐perpendicular shock usually has large perpendicular temperature anisotropy. The He2+ ring beam distribution and H+ temperature anisotropy can excite helium cyclotron waves and proton cyclotron waves, respectively. In this paper, we perform one‐dimensional hybrid simulations to investigate the competition between the helium cyclotron waves and proton cyclotron waves, and their influences on the evolution of He2+ and O6+ velocity distributions are also considered. When the wave spectrum is dominated by the helium cyclotron waves, He2+ and O6+ approximately move on the surface of a sphere, which results in shell‐like distributions for He2+and O6+. With the increase of the H+ temperature anisotropy T⊥p/T∥p, the amplitude of the proton cyclotron waves also increases. When it is sufficiently large and comparable with that of the helium cyclotron waves, the motions of He2+ and O6+ are irregular, which results in bi‐Maxwellian distributions of He2+and O6+. We also investigate the influence of the plasma β∥p on the excited ion cyclotron waves and the evolution of the He2+and O6+ distributions. The simultaneous observations for He2+ and O6+ in the downstream of shocks with Active Magnetospheric Particle Tracer Explorers (AMPTE)/CCE spacecraft have demonstrated their shell‐like distributions. The observed results verify the existence of the helium cyclotron waves downstream of supercritical quasi‐perpendicular shocks.
Geomagnetic storms driven by ICME‐ and CIR‐dominated solar wind
Authors: Denton M. H. , Borovsky J. E. , Skoug R. M. , Thomsen M. F. , Lavraud B. , Henderson M. G. , McPherron R. L. , Zhang J. C. , Liemohn M. W.
Published: May 2006

The interaction of the solar wind and the Earth's magnetosphere is complex and the phenomenology of the interaction is very different for solar wind dominated by interplanetary coronal mass ejections (ICMEs) compared to solar wind dominated by corotating interaction regions (CIRs). We perform a superposed epoch study of the effects of ICME‐ and CIR‐dominated solar wind upon the storm‐time plasma at geosynchronous orbit using data from the magnetospheric plasma analyzer (MPA) instruments on board seven Los Alamos National Laboratory (LANL) satellites. Using 78 ICME events and 32 CIR events, we examine the electron and ion plasma sheets that are formed during each type of solar wind driver, at energy‐per‐charge between ∼0.1 and 45 keV/q. The results demonstrate that CIR events produce a more significant modulation in the plasma sheet temperature than ICME events, whilst ICME events produce a more significant modulation in the plasma sheet density than CIR events. We attribute these differences to the average speed in the solar wind and a combination of the density of the solar wind and the ionospheric component of the plasma sheet, respectively. We also show that for CIR events, the magnitude of the spacecraft potential is, on average, significantly greater than during ICME‐events, with consequent effects upon the performance of instrumentation within this environment.
Plasma sheet expansion: Statistical characteristics
Authors: Ohtani S. , Mukai T.
Published: May 2006

The present study addresses the cause of plasma sheet expansion by statistically comparing the characteristics of lobe‐to‐plasma sheet (LB‐to‐PS) and PS‐to‐LB crossings observed by the Geotail satellite. Whereas the flapping motion of the magnetotail causes both types of crossing, the PS expansion (thinning) can be associated only with the LB‐to‐PS (PS‐to‐LB) crossing. Thus any systematic difference between the two types of crossing should reflect the difference between the PS expansion and thinning. Geotail observed more LB‐to‐PS crossings (744 events) than PS‐to‐LB crossings (640 events), and the preferred occurrence of the LB‐to‐PS crossing is more manifest closer to the Earth. It is found that at the PS‐to‐LB crossing, the plasma moves in the same direction as the boundary motion. At the LB‐to‐PS crossing, in contrast, the plasma often moves in the opposite direction to the boundary motion, indicating that there is a finite electric field in the frame of the boundary motion associated with the PS expansion. The PS expansion is therefore considered to be a manifestation of magnetic reconnection. That is, the PS expands because new PS flux tubes are added onto the preexisting PS. In the course of the PS expansion, the total pressure decreases, which may be interpreted in terms of the replacement of the preexisting PS plasma with new low‐pressure plasma originating from the tail lobe. The PS expansion is also characterized by relaxation (dipolarization) of the local magnetic field, which is inferred to be a direct consequence of reconnection. On the basis of recent reports of the lack of a one‐to‐one correspondence between reconnection and substorm onset, it is suggested that the PS expansion cannot be uniquely associated with a specific substorm phase.
Inference of postseismic deformation mechanisms of the 1923 Kanto earthquake
Authors: Pollitz Fred F. , Nyst Marleen , Nishimura Takuya , Thatcher Wayne
Published: May 2006

Coseismic slip associated with the M7.9, 1923 Kanto earthquake is fairly well understood, involving slip of up to 8 m along the Philippine Sea–Honshu interplate boundary under Sagami Bay and its onland extension. Postseismic deformation after the 1923 earthquake, however, is relatively poorly understood. We revisit the available deformation data in order to constrain possible mechanisms of postseismic deformation and to examine the consequences for associated stress changes in the surrounding crust. Data from two leveling lines and one tide gage station over the first 7–8 years postseismic period are of much greater amplitude than the corresponding expected interseismic deformation during the same period, making these data suitable for isolating the signal from postseismic deformation. We consider both viscoelastic models of asthenosphere relaxation and afterslip models. A distributed coseismic slip model presented by Pollitz et al. (2005), combined with prescribed parameters of a viscoelastic Earth model, yields predicted postseismic deformation that agrees with observed deformation on mainland Honshu from Tokyo to the Izu peninsula. Elsewhere (southern Miura peninsula; Boso peninsula), the considered viscoelastic models fail to predict observed deformation, and a model of ∼1 m shallow afterslip in the offshore region south of the Boso peninsula, with equivalent moment magnitude Mw = 7.0, adequately accounts for the observed deformation. Using the distributed coseismic slip model, layered viscoelastic structure, and a model of interseismic strain accumulation, we evaluate the post‐1923 stress evolution, including both the coseismic and accumulated postseismic stress changes and those stresses contributed by interseismic loading. We find that if account is made for the varying tectonic regime in the region, the occurrence of both immediate (first month) post‐1923 crustal aftershocks as well as recent regional crustal seismicity is consistent with the predicted stress pattern. This suggests that the influence of the 1923 earthquake on regional seismicity is fairly predictable and has persisted for at least seven decades following the earthquake.
Stratification effects by fine suspended sediment at low, medium, and very high concentrations
Authors: Winterwerp J. C.
Published: May 2006

This paper describes results of the second part of a study on stratification effects by cohesive and noncohesive sediment. Winterwerp (2001) applied classical stratified flow theory implemented in a one‐dimensional vertical numerical model (the 1DV POINT MODEL), showing that sediment‐induced stratification effects may occur at already fairly small suspended sediment concentrations (i.e., a few 100 mg/L). We also discussed a basic difference between the behavior of cohesive and noncohesive sediment, which emerges as a result of the large water content of mud flocs. In this paper we elaborate further on the hydrodynamic description of the transport of fine suspended sediment by analyzing field and laboratory observations over a very large range of concentrations. We propose a sediment stability diagram to explain some features of hyperconcentrated flows, such as those observed in the Yellow River. We show that the behavior of hyperconcentrated flows is affected largely by hindered settling effects reducing the energy required to keep the sediment in suspension. The hydrodynamic description of sediment transport is used to predict capacity conditions as a function of a dimensionless stream power, i.e., U3/hgWs. This prediction agrees favorably with observations reported in literature covering four orders of magnitude in suspended sediment concentration.
Variability of the relationship between the particulate backscattering coefficient and the volume scattering function measured at fixed angles
Authors: Chami M. , Marken E. , Stamnes J. J. , Khomenko G. , Korotaev G.
Published: May 2006

The particulate backscattering coefficient bbp is an inherent optical property that plays a central role in studies of ocean color remote sensing. Because of practical difficulties associated with measurements of the volume scattering function (VSF) over the whole backward hemisphere, bbp is currently derived using fixed‐angle backscattering sensors and applying a conversion factor for particulate backscattering, referred to as χp. The underlying assumptions of the fixed‐angle approach are as follows: (1) in the green band, χp is fairly constant in the angular range 100°–150° and (2) for a fixed scattering angle, χp is wavelength‐independent. In this study we investigated the variability of χp based on spectral measurements of the full VSF, both in situ and for algal culture in the laboratory. The in situ data used in our study were acquired in a coastal environment outside of phytoplankton blooms, whereas the laboratory data were representative for phytoplankton bloom conditions in oceanic waters. At 555 nm, χp was found to vary significantly in the angular range 100°–130°, and at 140°, χp was found to be weakly variable in nonblooming waters only. The spectral variability of χp was studied for the first time, and the spectral slopes of χp, measured in situ, were found to vary within ±6%. Under the assumption that χp(140°) is wavelength‐independent, the induced error in the estimates of bbp was found to be lower than 10%. The algal culture showed a much higher spectral variability in χp(±20%), which induced an error in the estimates of bbp up to ±25.8%.
OH, HO2, and OH reactivity during the PMTACS–NY Whiteface Mountain 2002 campaign: Observations and model comparison
Authors: Ren Xinrong , Brune William H. , Oliger Angelique , Metcalf Andrew R. , Simpas James B. , Shirley Terry , Schwab James J. , Bai Chunhong , Roychowdhury Utpal , Li Yongquan , Cai Chenxia , Demerjian Kenneth L. , He Yi , Zhou Xianliang , Gao Honglian , Hou Jian
Published: May 2006

Hydroxyl (OH), hydroperoxy (HO2) radicals, collectively known as HOx, and OH reactivity, were measured during the PMTACS–NY (PM2.5 Technology Assessment and Characteristics Study‐New York) summer 2002 intensive at Whiteface Mountain, Wilmington, New York. The measurement results of OH and HO2 for 4 weeks are presented. Diurnal cycles show that the average noontime maximum mixing ratios were about 0.11 pptv (2.6 × 106 cm−3) for OH and 20 pptv for HO2. Measured HO2 to OH ratios were typically between 40 and 400, which are greater than those obtained in polluted and semipolluted rural environments. Low but significant mixing ratios of OH and HO2 persisted into early evening and were frequently observed during nighttime, consistent with previous studies in different environments. Steady state OH and HO2 were calculated with a zero‐dimensional chemical model using a complete Regional Atmospheric Chemical Mechanism (RACM) and a parameterized RACM which was constrained to the measured OH reactivity. Good agreement was obtained between the complete RACM and the parameterized RACM models. On average, the complete RACM model reproduced the observed OH with a median measured‐to‐modeled OH ratio of 0.82 and daytime HO2 with a median measured‐to‐modeled HO2 ratio of 1.21. The reasonably good agreement in this study is inconsistent with the significant underestimation of OH in the Program for Research on Oxidants: Photochemistry, Emissions, and Transport in 1998 (PROPHET98) study at a similar forested site. HOx budget analysis indicates that OH was primarily from the photolysis of HONO and O3 during the day and from O3 + alkenes reactions at night. The main HOx loss was the self reaction of HO2. The good agreement between the measured and calculated OH reactivity in this environment contrasts with findings in the PROPHET2000 study, in which significant OH reactivity was missing and the missing OH reactivity was temperature‐dependent.
A reevaluation of airborne HOx observations from NASA field campaigns
Authors: Olson Jennifer R. , Crawford James H. , Chen Gao , Brune William H. , Faloona Ian C. , Tan David , Harder Hartwig , Martinez Monica
Published: May 2006

In situ observations of tropospheric HO2 obtained during four NASA airborne campaigns (SUCCESS, SONEX, PEM‐Tropics B and TRACE‐P) are reevaluated using the NASA Langley time‐dependent photochemical box model. Special attention is given to previously diagnosed discrepancies between observed and predicted HO2 which increase with higher NOx (NO + NO2) levels and at high solar zenith angles. This analysis shows that much of the model discrepancy at high NOx during SUCCESS can be attributed to modeling observations at timescales too long to capture the nonlinearity of HOx (OH+HO2) chemistry under highly variable conditions for NOx. Discrepancies at high NOx during SONEX can be moderated to a large extent by complete use of all available precursor observations. Differences between kinetic rate coefficients and photolysis frequencies available for previous studies versus current recommendations also explain some of the disparity. Each of these causes is shown to exert greater influence with increasing NOx because of both the chemical nonlinearity between HOx and NOx and the increased sensitivity of HOx to changes in sources at high NOx. In contrast, discrepancies at high solar zenith angles will persist until an adequate nighttime source of HOx can be identified. It is important to note that other data sets from ground‐based field studies show a similar discrepancy between observed and predicted HO2 for high NOx environments, and that the analysis presented here cannot resolve differences from those additional ground studies. Nevertheless, results from this study highlight important considerations in the application of box models to observationally based predictions of HOx radicals.
Cassini imaging of Saturn: Southern hemisphere winds and vortices
Authors: Vasavada A. R. , Hörst S. M. , Kennedy M. R. , Ingersoll A. P. , Porco C. C. , Del Genio A. D. , West R. A.
Published: May 2006

High‐resolution images of Saturn's southern hemisphere acquired by the Cassini Imaging Science Subsystem between February and October 2004 are used to create maps of cloud morphology at several wavelengths, to derive zonal winds, and to characterize the distribution, frequency, size, morphology, color, behavior, and lifetime of vortices. Nonequatorial wind measurements display only minor differences from those collected since 1981 and reveal a strong, prograde flow near the pole. The region just southward of the velocity minimum at 40.7°S is especially active, containing numerous vortices, some generated in the proximity of convective storms. The two eastward jets nearest the pole display periodicity in their longitudinal structure, but no direct analogs to the northern hemisphere's polar hexagon or ribbon waves were observed. Characteristics of winds and vortices are compared with those of Saturn's northern hemisphere and Jupiter's atmosphere.
Radio occultation measurements of transient eddies in the northern hemisphere of Mars
Authors: Hinson D. P.
Published: May 2006

We have characterized the behavior of transient eddies in the northern hemisphere of Mars through analysis of Radio Science (RS) occultation data from Mars Global Surveyor (MGS). The “weather” in the lowest scale height above the surface at 55°N–80°N is dominated by shallow, eastward moving baroclinic eddies distinguished by their intensity and coherence. The vertical structure of these eddies is fully resolved by the RS measurements, which also yield unique estimates of the near‐surface meridional winds implied by geostrophic balance. We identified and characterized the most prominent eddies through space‐time analysis of RS measurements of geopotential height at 610 Pa, a few kilometers above the surface. Eddy activity appears as well‐defined modes with zonal wave numbers 1–3, and variations in the amplitudes of these modes tend to be anticorrelated so that a large amplitude in one mode is often accompanied by a small amplitude in the others. The wave number and period of the dominant mode shift at intervals of 30–50 sols. Eddy winds near the surface vary distinctively with season in response to changes in eddy amplitude and zonal wave number. The meridional winds peak sharply in two seasonal windows, one in early‐to‐middle autumn and the other in middle‐to‐late winter, separated by a lull around winter solstice. Comparisons with previous results reveal close connections with the transient eddies observed by the Viking Landers and with distinctive southward moving frontal dust storms observed by the MGS Mars Orbiter Camera.
Radio science measurements of atmospheric refractivity with Mars Global Surveyor
Authors: Cahoy K. L. , Hinson D. P. , Tyler G. L.
Published: May 2006

Radio occultation experiments with Mars Global Surveyor measure the refractive index of the Martian atmosphere from the surface to ~250 km in geopotential height. Refractivity is proportional to neutral density at low altitudes and electron density at high altitudes, with a transition at ~75 km. We use weighted least squares to decompose zonal refractivity variations into amplitudes and phases for observed wave numbers k = 1–4 over the entire altitude range and use the results to analyze atmospheric structure and dynamics. The data set consists of 147 refractivity profiles acquired in December 2000 at summer solstice in the Martian northern hemisphere. The measurements are at an essentially fixed local time (sunrise) and at latitudes from 67° to 70°N. Thermal tides appear to be responsible for much of the observed ionospheric structure from 80 to 220 km. Tides modulate the neutral density, which in turn, controls the height at which the ionosphere forms. The resulting longitude‐dependent vertical displacement of the ionosphere generates distinctive structure in the fitted amplitudes, particularly at k = 3, within ±50 km of the electron density peak height. Our k = 3 observations are consistent with an eastward propagating semidiurnal tide with zonal wave number 1. Relative to previous results, our analysis extends the characterization of tides to altitudes well above and below the electron density peak. In the neutral atmosphere, refractivity variations from the surface to 50 km appear to arise from stationary Rossby waves. Upon examining the full vertical range, stationary waves appear to dominate altitudes below ~75 km, and thermal tides dominate altitudes above this transition region.
Topographic characteristics of the submarine Taiwan orogen
Authors: Ramsey L. A. , Hovius N. , Lague D. , Liu C.‐S.
Published: May 2006

A complete digital elevation and bathymetry model of Taiwan provides the opportunity to characterize the topography of an emerging mountain belt. The orogen appears to form a continuous wedge of constant slope extending from the subaerial peaks to the submarine basin. We compare submarine channel systems from the east coast of Taiwan with their subaerial counterparts and document a number of fundamental similarities between the two environments. The submarine channel systems form a dendritic network with distinct hillslopes and channels. There is minimal sediment input from the subaerial landscape and sea level changes are insignificant, suggesting that the submarine topography is sculpted by offshore processes alone. We implement a range of geomorphic criteria, widely applied to subaerial digital elevation models, and explore the erosional processes responsible for sculpting the submarine and subaerial environments. The headwaters of the submarine channels have steep, straight slopes and a low slope‐area scaling exponent, reminiscent of subaerial headwaters that are dominated by bedrock landslides. The main trunk streams offshore have concave‐up longitudinal profiles, extensive knickpoints, and a slope‐area scaling exponent similar in form to the onshore fluvial domain. We compare the driving mechanisms of the likely offshore erosional processes, primarily debris flows and turbidity currents, with subaerial fluvial incision. The results have important implications for reading the geomorphic signals of the submarine and subaerial landscapes, for understanding the links between the onshore and offshore environments, and, more widely, for focusing the future research of the submarine slope.
Sensitivity of the subpolar North Atlantic to Last Glacial Maximum surface forcing and sea ice distribution in an eddy‐permitting regional ocean model
Authors: Yang Duo , Myers Paul G. , Bush Andrew B. G.
Published: May 2006

The impact of paleoatmospheric forcing and sea ice distribution on the circulation of the subpolar North Atlantic is examined in a regional eddy‐permitting ocean model. We focus on water mass formation and the pathway of the North Atlantic Current. Paleofluxes are obtained from a coupled atmospheric general circulation model, while the seasonal sea ice cover is based on a pair of Last Glacial Maximum sea ice reconstructions. Labrador Sea Water formation, the pathway of the North Atlantic Current, and the strength of the Atlantic Meridional Overturning Circulation are found to be dependent on the structure of the sea ice representation. Here, the key role played by the sea ice is its isolation of the underlying ocean from the wintertime atmospheric fluxes. The results highlight the need for accurate seasonal sea ice fields for validating paleomodeling simulations.
Young displacements on the Atacama Fault System, northern Chile from field observations and cosmogenic 21Ne concentrations
Authors: González L. Gabriel , Dunai Tibor , Carrizo Daniel , Allmendinger Richard
Published: May 2006

We present the first numerical age constraint for young deformation of the Atacama Fault System (AFS) in northern Chile. The young activity of the AFS is expressed by several fault scarps which affects alluvial fan sediments of the eastern side of the Coastal Cordillera (23°30′–23°42′S). Detailed mapping of alluvial fans reveals a complex relationship between fault motion, erosion and alluvial fan development. An older group of alluvial fans became inactive prior to the scarp formation. Younger alluvial fans, arising directly from feeder channels and entrenched in the fault scarps, posts date the scarp formation. The youngest slip on the AFS is recorded by headward eroding channels entrenched across the scarp which are in turn displaced vertically 0.3–0.5 m by the fault. Quartz fragments in four sites on the older inactive fan group were analyzed for cosmogenic 21Ne concentrations yielding an average age of 424 ± 151 ka, the upper limit for the recent activity of the fault. Combined with the height of fault scarp, we calculate a 0.01 mm/yr minimum vertical fault slip rate. Thus young displacement on the AFS is Quaternary in age and confined to the late Pleistocene.
Faults as conduit‐barrier systems to fluid flow in siliciclastic sedimentary aquifers
Authors: Bense V. F. , Person M. A.
Published: May 2006

We argue that the observed conduit‐barrier behavior of fault zones in siliciclastic sedimentary aquifer systems can be understood by considering a strongly anisotropic hydraulic structure in the fault. Hydraulic anisotropy in the fault is expected from a variety of mechanisms including clay‐smearing, drag of sand, grain re‐orientation and vertical segmentation of the fault plane. In this paper, we present an algorithm to predict fault zone width, lithological heterogeneity and hydraulic anisotropy. Estimation of these parameters is based upon the amount of fault throw and the clay‐content of the lithologies flanking the fault zone. A suite of steady‐state flow models are presented using an idealized stratigraphy consisting of alternating clay and sand‐rich layers that are offset by a fault zone. These conceptual simulations show the impact of a fault zone on shallow (<500 m) fluid flow patterns and solute transport for different scenarios of fault throw. Fault width varies along the fault zone and increases from an average width of ~2 m for a throw of 50 m to ~8 m for a throw of 200 m. Hydraulic anisotropy in the fault zone in these scenarios is predicted to range between two to three orders of magnitude. Our results show that faults can form a preferential path way between aquifers at different depths over vertical distances of several hundreds of meters (that are otherwise separated by confining units) when fault permeability is strongly anisotropic. However, in the same scenario anomalously high hydraulic head gradients across the fault would still suggest that they act as an effective barrier to lateral groundwater flow. This has important implications for the assessment of the risk of a spread of contaminated groundwater or the reconstruction of hydrocarbon migration within sedimentary basins.
Simulation of solute transport in a heterogeneous vadose zone describing the hydraulic properties using a multistep stochastic approach
Authors: Oliveira Leonardo I. , Demond Avery H. , Abriola Linda M. , Goovaerts Pierre
Published: May 2006

The simulation of conservative solute transport in a heterogeneous unsaturated soil depends on the description of spatial variability of soil hydraulic and chemical properties. The data from the Las Cruces Trench Site were used to explore the impact of alternative ways of describing the variability of hydraulic properties. Three different approaches were considered: Miller and Miller scaling, Leverett scaling, and a multistep approach involving categorization of water retention curves. Conditional sequential geostatistical simulation was used to generate equally probable realizations of soil properties for each approach, and these realizations were then used as input to a numerical simulator to quantify the resultant uncertainty in solute transport predictions. Simulation results show that the scaling techniques seem to oversimplify the description of heterogeneity in the Las Cruces Trench, leading to very narrow spaces of uncertainty. Because the multistep approach allows the reproduction of existing patterns of continuity of soil classes and of contrasting values of hydraulic properties in the field, it led to solute plumes that split into several preferential pathways that were not observed in the simulations based on the scaling approaches, which increased the standard deviation of the solute plume's moments. The results indicate that measurements of both water retention curves and saturated hydraulic conductivity need to be collected for more realistic, conservative studies of flow in heterogeneous unsaturated soils.
A two‐radius circular array method: Inferring phase velocities of Love waves using microtremor records
Authors: Tada Taku , Cho Ikuo , Shinozaki Yuzo
Published: May 2006

We present a new method to estimate phase velocities of Love waves from horizontal‐motion seismograms of microtremors, obtained with seismic sensors placed around two circumferences of different radii, under the assumption that the fundamental mode dominates. We applied our new method to field data acquired at a test site where the shallow underground seismic velocity profile is known, and have confirmed that the phase velocities of the fundamental‐mode Love waves could be inferred with sufficient precision within certain wavelength ranges. Outside the wavelength ranges suitable for analysis, the “spectral ratio,” an intermediary quantity calculated from measurement records prior to phase velocity evaluation, deviated from theoretical expectations. The pattern of deviations could satisfactorily be accounted for by considering three factors theoretically: the presence of higher‐mode surface waves, directional aliasing related to the finite number of sensors, and the presence of incoherent noise.
Excess pore pressures within subducting sediments: Does the proportion of accreted versus subducted sediments matter?
Authors: Screaton E.
Published: May 2006

Although previous numerical modeling studies have examined pore pressures in both accretionary and non‐accretionary subduction zones, they have not addressed the question of whether the proportion of accreted versus subducted sediments significantly affects pore pressures. This modeling study used consistent parameters to compare excess pore pressures directly below the decollement for varying proportions of accreted sediment. Within the initial 5 to 12 kilometers arcward of the deformation front, subduction zones with lesser accretion thickness show lower simulated excess pore pressures than those with greater accretion thickness due to the ease of fluid escape when overlying wedge sediments are thin. However, at greater distances arcward of the deformation front, the magnitude of excess pore pressures significantly increases and the excess pore pressures peak further arcward as the proportion of underthrust sediments increases. This difference suggests that the proportion of accreted versus subducted sediment could potentially affect seismogenesis.