bluuebunny/crossref_metadata_2025 huggingface dataset:
Deformity secondary to bilateral incomplete ossification of the humeral condyle in a German Shorthaired Pointer dog
Authors: DeCamp C. E. , Agnello C. , Steficek B. A. , von Pfeil D. J. F.
Published: September 2010

A five-month-old male, German Shorthaired Pointer dog was presented for severe, bilateral, thoracic-limb-lameness, with elbow swelling, pain, and crepitus. Radiography and computed tomography confirmed bilateral incomplete ossification of the humeral condyles (IOHC), with a non-displaced incomplete fracture of the left medial epicondylar crest and condylar deformity, characterised by enlargement of the trochleas with extension of the disto-medial aspect of the bone below the normal elbow joint level, and a deformed proximo-medial aspect of the ulna and radius. Transcondylar lag screws were placed bilaterally in an attempt to prevent fracture. Microscopic examination of biopsies, harvested from both humeral condyles, was supportive of IOHC. Six years after surgery, radiographs showed severe osteoarthritis and it appeared that fusion of the humeral condyles had not occurred. The dog followed an active life style until 10 years after surgery when the elbows showed almost no observable range-of-motion. However, discomfort was evident only after heavy exercise. Incomplete ossification of the humeral condyles may be associated with osteoarthritis, risk for non-union, implant failure, or secondary condylar fracture. This dog maintained good limb function despite these concerns, and despite bilateral humeral condylar deformity as well as development of severe osteoarthritis. This is the first report of a German Shorthaired Pointer dog with IOHC and the first histological description supportive of this condition in a five-month-old dog.
Comparison of four commercial devices to measure limb circumference in dogs
Authors: Roush J. K. , Unis M. D. , Wodiske T. , Baker S. G.
Published: September 2010

We evaluated four measurement devices for obtaining circumferential measurements at four locations on the canine hindlimb and forelimb. We hypothesised that these devices would be consistent and precise in the hands of veterinary professionals with varying experience levels. Circumferential measurements were made in five dogs with no history or clinical evidence of orthopaedic disease. Measurements were obtained in triplicate by three observers at mid-thigh, tibial tuberosity, hock and carpus bilaterally. Results indicated a significantly larger measurement at the left mid-thigh region than the right, with no significant differences between limbs noted at other sites. Measurements with a tape measure and a retractable tape measure resulted in significantly smaller values at each site than an ergonomic measuring tape and a circumference measuring tape. Interobserver variation was 3.6 times higher than intraob-server variation. These results illustrate the importance of consistency when obtaining these measurements. Sequential circumference measurements should be made by the same individual using the same device to decrease measurement variability. Devices were equally precise for repeat measurements although the absolute measurement varied by device.
Double pelvic osteotomy for the treatment of hip dysplasia in young dogs
Authors: Vezzoni A. , Boiocchi S. , Vanelli A. B. , Bronzo V. , Vezzoni L.
Published: September 2010

The aim of this study was to evaluate the feasibility of the double pelvic osteotomy (DPO) (osteotomy of the ilium and pubis) to treat clinical cases of hip dyplasia in young dogs instead of performing a triple pelvic osteotomy (TPO) (osteotomy of the ilium, pubis, and ischium). Candidates for DPO were 4.5- to nine-month-old dogs with coxofemoral joint subluxation and laxity, indicative of susceptibility to future development of severe hip dysplasia. The angle of reduction (AR) and angle of subluxation (AS) with Ortolani's sign, Norberg angle (NA), percentage of femoral head (PC) covered by the acetabulum, and the pelvic diameters and their relationships were measured clinically and radiographically before and after surgery. The surgical technique was similar to the TPO technique, but excluded ischiatic osteotomy. A DPO was carried out in 53 joints of 34 dogs AR and AS values immediately postoperatively and at the oneand two-month follow-up examinations were significantly lower than the preoperative values (p <0.01). The complications en-countered were mainly represented by implant failure (3.5%), partial plate pull-out (9.4%), and incomplete fracture of the ischial table (7.5%). Changes in PC and NA values obtained immediately after surgery and at the first and second follow-up examinations were significantly greater (p <0.01 both) than values obtained before surgery. Sufficient acetabular ventroversion was achieved to counteract joint subluxation and the modifications of AR and AS. The NA and PC direct postoperative values reflected a significant improvement in the dorsal acetabular coverage.

Clinical relevance: Restoration of normal joint congruity (PC from 50 to 72%) and maintenance of the pelvic geometry without pelvic narrowing were the most intriguing features of DPO. The complications observed were greatly reduced when using dedicated DPO plates. Based on our experience, the morbidity after unilateral and bilateral DPO was lower than after TPO because elimination of the ischiatic osteotomy allowed for increased stability of the pelvis. The surgical technique of DPO was a little more demanding than TPO because of the difficulty in handling and rotating the acetabular iliac segment, but this difficulty was offset by elimination of ischial osteotomy.
A Critical Analysis of the Motivational Factors that Influence Event Attendance in Family Groups
Authors: Foster Katie , Robinson Peter
Published: September 2010

The aim of this study was to identify the motivational factors that influence families to attend events as there is limited information available regarding family events motivation. This study bridges the gap between event organizers and the “family” to find out which events
families choose to attend and why. Results identified that children are a major determining factor within the event decision-making process for a family. Results also show that previous research regarding “top motivational factors” for individuals is not the same for families as
they are willing to compromise and attend an event that their children will find satisfying, which, in turn, results in satisfied parents and a successful day out. Families are not interested in the novelty or uniqueness of an event; they just want to spend time together.
Summer Camps as a Means to Recruit Prospective College Students
Authors: Kwok Linchi , Fowler Deborah C. , Yuan Jingxue (Jessica)
Published: September 2010

Recent literature has revealed summer camps, as educational and scientific events, can be used as an effective tool to recruit prospective college students in engineering, nursing, and some science disciplines. The purpose of this study was to test six research questions regarding the
relationships between summer camp participants' satisfaction level and their intention to attend the camp again, intention to recommend the camp to others, intention to attend other camps hosted by the same academic program, intention to attend other camps hosted by the same university, intention
to apply to the host academic program after high school, and intention to apply to the host university after high school. Fifty-eight campers from a Fashion Camp and a Native American Camp participated in this study. Quantitative data analysis with one-tail Pearson's correlation helped answer
the research questions and confirmed the relationships between variables exist. Practical implications, limitations, and agenda for future studies are discussed.
The Economic Impact of College Sporting Events: A Case Study of Division I-A Football Games
Authors: Lee Sangkwon , Harris John , Lyberger Mark
Published: September 2010

In sport management, economic impact studies are often used to estimate the economic benefits of sport events, sports facilities, and sports teams. Many studies have focused on the measurement of hallmark or mega-events but few have focused on the impact of smaller scale repetitive
events. The objective of this study was to estimate total spending and economic impact on the local economy of visitors to college football games and then to assess the value of the sport to the community. Using the input–output model, the study calculated the economic impact of these
events on sales, income, value-added, and employment of the community. Key misapplications in economic impact analysis and costs associated with sporting events are also discussed.
Worldwide correlations of mechanical properties and green wood density
Authors: Niklas Karl J. , Spatz Hanns‐Christof
Published: September 2010

• Premise of the study: The density of wood is highly correlated with the ability of stems and roots to resist bending or twisting, which is important for evaluating the mechanical behavior of trees. It also provides a measure of carbon storage, which is an important variable in modeling ecosystem processes and tree construction costs. However, most measurements of the density and mechanical properties of wood have little direct bearing on understanding the biomechanics of living plants because they are based on kiln‐ or air‐dried samples.

• Methods: Here, we present and analyze the relationships between four important mechanical properties (Young's modulus, the modulus of rupture, and the maximum strength in shearing and in compression) and the density of green wood (i.e., wood at 50% moisture content) from a worldwide, taxonomically broad spectrum of 161 species.

• Key results: These data indicate that each of the mechanical properties disproportionately increases across species with increasing green wood density, i.e., stems composed of denser green wood are disproportionately stiffer and stronger than stems with equivalent cross‐sections composed of less dense green wood.

• Conclusions: Although denser wood may have a higher carbon construction cost, the mechanical benefits of denser woods likely outweigh the extra cost.
The Anatomy and Pathology of the Lesser SAC: Implications for Peritoneal Dialysis
Authors: Shrestha Badri M. , Brown Peter W.G. , Wilkie Martin E. , Raftery Andrew T.
Published: September 2010

Pathological conditions involving the lesser sac of the peritoneal cavity in patients on peritoneal dialysis (PD) can pose significant diagnostic and therapeutic challenges. Lack of appreciation of these challenges may delay diagnosis and compromise outcome. A case series by Li and colleagues in this issue of Peritoneal Dialysis International highlights the diagnostic challenges presented by lesser sac infection in PD patients, and in this accompanying commentary we discuss the development and anatomy of the lesser sac, as well as the pathological conditions and investigations relevant to the management of patients on PD.
Structure–activity relationships of HCV NS3 protease inhibitors evaluated on the drug-resistant variants A156T and D168V
Authors: Örtqvist Pernilla , Vema Aparna , Ehrenberg Angelica E , Dahl Göran , Rönn Robert , Åkerblom Eva , Karlén Anders , Danielson U Helena , Sandström Anja
Published: September 2010

Background

HCV infections are a serious threat to public health. An important drug target is the NS3 protease, for which several inhibitors are in clinical trials. Because of the high mutation rate of the virus, resistance against any HCV-specific drug is likely to become a substantial problem. Structure–activity data for the major resistant variants are therefore needed to guide future designs of protease inhibitors.

Methods

The inhibitory potency of tripeptide NS3 protease inhibitors, with either a P2 proline or phenylglycine, in combination with different P3 and P1-P1’ groups, was assessed in enzyme activity assays using the full-length NS3 protein with known resistance- conferring substitutions A156T or D168V. The results obtained from these variants were compared with the inhibition of the wild-type enzyme. Molecular modelling was used to rationalize the biochemical results.

Results

Inhibitors combining the P2 proline and P1 (1 R,2 S)-1-amino-2-vinylcyclopropyl-carboxylic acid (vinylACCA) lost much of their potency on the resistant variants. Exchange of the P2 proline for phenylglycine yielded inhibitors that were equipotent on the wild-type and on the A156T and D168V variants. The same result was obtained from the combination of either the P2 residue with a norvaline or an aromatic scaffold in the P1 position.

Conclusions

The combination of a substituted P2 proline and P1 vinylACCA appears to be the main problem behind the observed resistance. Molecular modelling suggests an enforced change in binding conformation for the P2 proline- based inhibitors, whereas the phenylglycine-based inhibitors retained their wild-type binding conformation in the substituted forms of the enzyme.
Antibiotic-Coated Spacers for Total Hip Arthroplasty Infection
Authors: Bloomfield Michael R. , Klika Alison K. , Barsoum Wael K.
Published: September 2010

Total hip arthroplasty (THA) infection imposes a significant burden on the patient and the health care system. Two-stage revision with interval placement of an antibiotic-cement spacer is the standard of care for chronic periprosthetic infections. This treatment allows for the direct delivery of antibiotics to the infected tissues, and maintains soft tissue tension to facilitate the re-implantation procedure. Evidence suggests that articulating spacers, compared to nonarticulating designs, enhance postoperative ambulation and make the second-stage procedure less difficult. Prefabricated spacers are easy to use; however, they cannot be used to alter the antibiotic composition and dosage. Custom-molded spacers prepared in the operating room from commercially available kits are a popular option; however, like prefabricated spacers, limited sizes are available and thus, they may be contraindicated in situations with significant bone loss. Custom-made total hip spacers are significantly less expensive than commercially-available options, are useful in cases of bone loss, and optimize patient function prior to re-implantation. An inexpensive cemented femoral stem is covered with antibiotic-loaded bone cement. This is done once the cement has the consistency of dough to prevent interdigitation with the host femur. The authors use at least 3.6 g of tobramycin and 1 g of vancomycin per packet of cement. A thin polyethylene is cemented into the acetabulum, followed by placement of the femoral prosthesis. Combined component position must be optimized to prevent instability.
Total Hip Arthroplasty in Patients with Down Syndrome
Authors: Kosashvili Yona , Taylor Drew , Backstein David , Safir Oleg , Gross Allan , Lakstein Dror
Published: September 2010

Hip osteoarthritis is prevalent in 8% to 28% of patients with Down syndrome. Presence of disabling hip pain is increased along with prolonged life expectancy, suggesting total hip arthroplasty (THA). Seven consecutive patients (9 hips) with Down syndrome underwent primary THA. Coxarthrosis was secondary to developmental hip dysplasia in 6 patients and slipped capital epiphysis in 1 patient. In 5 patients (7 hips), a previous hip surgery was performed. Average clinical and radiological follow-up was 9.9±6.4 years (range, 2–22.5 years; median, 9.3 years). Average patient age at THA was 34.8±7.5 years (range, 25– 47 years; median, 35.4 years). In 2 patients (3 hips), a trochanteric slide was used for the surgical approach, while a lateral transgluteal approach was used in the remaining patients. One-way analysis of variance test was used to compare Harris Hip Scores (HHS) at postoperative follow-up.

Harris Hip Scores improved significantly (
P
=.008) from 4.1±15.1 (range, 18.5–65; median, 45) to 84.8.3±7.7 (range, 70–93; median, 85.8) at 4-year follow-up. Harris Hip Scores (average, 70.9±6.2; range, 66.5–80; median, 68) remained essentially unchanged (
P
=.43) at 8-year follow-up. Two patients required revision THA for stem loosening at 6 and 16 years post-THA, respectively. The first patient is 7 years post-revision and ambulates without aids. The second patient is 6.1 years post-revision and ambulates with a walker. Six of the THAs required a constrained liner. No dislocations or deep infections were encountered. At last follow-up, all patients had a functional range of motion without evidence of discomfort related to their THA.
DVT Prophylaxis: Better Living Through Chemistry: Affirms
Authors: Pellegrini Vincent D.
Published: September 2010

Venous thromboembolism remains the most common cause of hospital readmission and death after total joint arthroplasty. The 2008 American College of Chest Physicians (ACCP) guidelines, based on prospective randomized clinical trials with a venography endpoint, endorse the use of low-molecular-weight heparin, fondaparinux, or adjusted dose warfarin (target international normalized ratio, 2.5; range, 2–3) for up to 35 days after total hip arthroplasty (THA) and total knee arthroplasty (TKA). In the past, the ACCP has recommended against the use of aspirin, graduated compression stockings, or venous compression devices as the sole means of prophylaxis, but in 2008 they first recommended the “optimal use of mechanical thromboprophylaxis with venous foot pumps or intermittent pneumatic compression devices” in patients undergoing total joint arthroplasty who “have a high risk of bleeding.” When the high risk subsides, pharmacologic thromboprophylaxis is substituted for, or added to, mechanical methods.

Fractionated heparins and pentasaccharide are the most effective agents in reducing venographic deep venous thrombosis (DVT) after total joint arthroplasty with residual clot rates <5% after THA and 20% after TKA, but major or clinically meaningful bleeding occurs in 3% to 5% of patients. Newer Xa and thrombin inhibitors enjoy greater efficacy with equal or higher bleeding rates. Low-intensity warfarin (target international normalized ratio, 2.0) combines safety (bleeding rates <1%) with efficacy (readmission for clinical DVT or pulmonary embolism 0.2%) after total joint arthroplasty. Warfarin represents a therapeutic compromise by preventing clinical events in exchange for a lower bleeding rate; genetic testing will likely simplify warfarin use and reduce outlier responders.
Perspectives on Parenthood and Working of Female Athletic Trainers in the Secondary School and Collegiate Settings
Authors: Kahanov Leamor , Loebsack Alice R. , Masucci Matthew A. , Roberts Jeff
Published: September 2010

Context:

Female athletic trainers (ATs) are currently underrepresented in the collegiate setting. Parenting and family obligations may play a role in this underrepresentation.

Objective:

To examine female ATs' perspectives on parenting and working in the secondary school and collegiate employment settings.

Design:

Cross-sectional study.

Setting:

Online survey.

Patients or Other Participants:

A total of 1000 nonstudent, female certified ATs who were currently members of the National Athletic Trainers' Association.

Main Outcome Measure(s):

An original survey was developed to assess perceptions related to motherhood and work responsibilities. Descriptive statistics were used to assess age, years of experience as a certified AT, employment position, and parent or nonparent status. A correlation matrix was conducted to determine factors among parent and nonparent status, perceptions of motherhood, and employment-setting decisions.

Results:

Of the 1000 surveys sent via e-mail, 411 (41.1%) female ATs responded. Responses indicated that a majority of the female ATs worked in the secondary school setting. Sixty-one percent of the respondents did not have children. Past female ATs' experiences indicated a perception that motherhood created more challenges or struggles (or both) in the work and family settings. Whether parents considered children a factor in employment-setting changes produced conflicting results: no significant correlations or differences were found among responses.

Conclusions:

Parenting considerations had influences on both the home and employment settings. Although parents and nonparents had different views on the implications of parenting in the workplace, both groups agreed that parenting could affect the work environment and the choice to change employment settings and careers. Administrative decisions need to be considered in relation to parenting concerns. Mentoring that includes employment-setting choices relative to life goals should be provided to ATs, regardless of sex.
The effect of the exceptionally mild European winter of 2006‐2007 on temperature and oxygen profiles in lakes in Switzerland: A foretaste of the future?
Authors: Rempfer Johannes , Livingstone David M. , Blodau Christian , Forster Richard , Niederhauser Pius , Kipfer Rolf
Published: September 2010

The European winter of 2006–2007 was unusually mild, with record high mean winter air temperatures comparable with those predicted to become the norm by the end of the current century as a result of climate warming. In Lake Zurich and Greifensee, two neighboring Swiss perialpine lakes with several decades of data, mean lake temperatures for this winter were the highest ever recorded, as was thermal stability. Associated with the high thermal stability, mean winter oxygen concentrations in Lake Zurich were unusually high in the epilimnion and metalimnion, but normal in the hypolimnion. In Greifensee, however, which is much shallower, mean winter oxygen concentrations did not deviate substantially from the norm anywhere in the water column. From 17–19 January 2007, an unusually severe cyclonic storm, “Kyrill”, traversed Europe. Monthly oxygen profiles suggest that the stabilizing effect of the mild winter on the two lakes was greatest before the occurrence of the storm, and that wind mixing resulted in a deepening of the mixed layer in both lakes. The mixing was able to encompass the entire water column of Greifensee, but not of Lake Zurich. These results, supported by more limited data from two other neighboring lakes, suggest that climate warming will likely inhibit complete mixing of some deep, temperate, normally monomictic lakes in winter even when extremely intense cyclonic storms occur. In shallower lakes, however, complete mixing is unlikely to be inhibited.
The association between biogenic and inorganic minerals and the amino acid composition of settling particles
Authors: Salter I. , Kemp A. E. S. , Lampitt R. S. , Gledhill M.
Published: September 2010

To test the hypothesis that calcium carbonate (rather than opal) carries most organic carbon to the deep sea, total hydrolysable amino acid (THAA) analysis was applied to deep‐sea (3000 m) sediment trap material from the northeast Atlantic (PAP Site), a variable but intrinsically carbonate‐dominated system. THAAs were analyzed in conjunction with total organic carbon, biogenic silica, calcium carbonate, and inferred lithogenic fluxes. The THAA‐based degradation state of organic carbon could not be systematically explained by changes in the flux of different mineral phases, which could account for only 16% of the observed variability. In addition amino acid parameters indicative of source organisms indicate that diatom cell walls are an important residual component of organic carbon reaching the deep ocean, a finding supported by comparison with data from previous studies of diverse oceanic environments. Finally, during 2001, very high organic carbon fluxes were associated with elevated lithogenic fluxes and low organic matter degradation relative to surrounding years. In accordance with other recent experimental and observational studies, the data indicate that under specific export scenarios, lithogenic fluxes can act as highly significant mediators of organic carbon transfer to the deep ocean.
A multivariate approach to large‐scale variation in marine planktonic copepod diversity and its environmental correlates
Authors: Rombouts Isabelle , Beaugrand Grégory , Ibañez Frédéric , Gasparini Stéphane , Chiba Sanae , Legendre Louis
Published: September 2010

We have investigated the relationships between covariations in environmental variables and variations in distributions of marine copepod diversity over an extensive latitudinal range from 86.5°N to 46.5°S. For this purpose, 7 data sets (representing 13,713 samples) of copepod species composition data and 11 environmental data sets were assembled. Principal components analysis was applied to investigate the relationships among the mean and seasonal variations in environmental descriptors (ocean temperature, chlorophyll a [Chl a], net primary production, and other physical and chemical properties of the ocean) and their relationships with spatial variations in copepod diversity. High copepod diversity corresponded to a combination of high ocean temperature and salinity and low Chl a and nutrient concentrations (nitrate, silicate, phosphate). To a lesser extent, high‐diversity regions were also correlated to low seasonal variability in oxygen, ocean temperature, and mixed‐layer depth. Regression on principal components provided a robust prediction of global copepod diversity (R2 = 0.45, p < 0.001) as our subset of environmental data was representative of the full range of environmental variability that occurs globally.
On the role of natural water level fluctuation in structuring littoral benthic macroinvertebrate community composition in lakes
Authors: White Michael S. , Xenopoulos Marguerite A. , Metcalfe Robert A. , Somers Keith M.
Published: September 2010

We used traditional hydrologic endpoints and extracted novel water‐level fluctuation (WLF) characteristics through principal components analysis (PCA), to determine the relationship between WLF and rocky littoral benthic macroinvertebrate (BMI) richness in 16 boreal lakes. Yearly WLF amplitude (maximum minus minimum water levels) ranged from 35.9 cm to 157.5 cm. Using PCA we derived a new variable D80‐D210 (31 March minus 01 August) as a surrogate for change in mean water level and potential habitat squeeze (loss). Analyses of BMI richness with several physicochemical variables, including water quality (8), habitat variability (4), lake and basin morphology (6), land classification (28), water temperature (8), hydrology (9), and PCA axes (10) resulted in only three significant relationships. We found a classic species‐area relationship, as BMI richness increases with increasing lake area (r2 = 0.38linear, r2 = 0.69unimodal). Similarly, as littoral slope increases macroinvertebrate richness decreases (r2 = 0.32linear). Most importantly, lower water levels, quantified using D80‐D210, have higher macroinvertebrate richness (r2 = 0.38linear). Together these results suggest that a habitat squeeze in littoral areas is the direct result of lower mean water levels and that relatively small changes in natural WLF can be associated with changes in BMI communities.
Feedback effects in a coastal canopy‐forming submersed plant bed
Authors: Gruber Renee K. , Kemp W. Michael
Published: September 2010

Although physical and biogeochemical properties of an environment determine distribution and health of biota, some organisms modify habitat conditions through complex interactions with their surroundings. We quantified effects of the canopy‐forming submersed plant species Stuckenia pectinata on local hydrodynamics and explored resulting positive and negative feedbacks on plant growth. Measurements of waves and tidal currents were made outside, at the edge of, and within a plant bed located in the mesohaline region of Chesapeake Bay. Clear feedback effects on light, nutrients, and sediments were observed, and were found to vary seasonally with plant growth cycle. During the June period of peak plant biomass, significant wave heights were attenuated by ~ 37% within the plant stand; this resulted in an ~ 60% reduction of total suspended solids, which was stable and relatively unaffected by periods of high wind speed or water depth. Deployments of artificial substrates showed that epiphytic accumulation was greatly reduced within the plant bed, further increasing available light for plants to 25% of incoming irradiance (as compared to 0.2% outside the plant bed). In addition, higher particle trapping rates and sediment organic content augmented bed pore‐water nutrient pools (CO2, NH4+, PO43− sufficiently to satisfy plant demands. These processes generated negative feedback effects on plant growth, including elevated pore‐water sulfide (> 700 µmol L−1) and depressed water‐column O2 concentrations (< 2 mg L−1), but levels were ephemeral and generally outside reported stress thresholds. Dominant positive feedbacks provide an explanation for bed survival in this environment despite degraded water quality during summer months.
Photodegradation of the brevetoxin PbTx‐2 in coastal seawater
Authors: Kieber Robert J. , Pitt Jaclyn , Skrabal Stephen A. , Wright Jeffrey L. C.
Published: September 2010

The photodegradation rate of the brevetoxin analog PbTx‐2 was investigated in a variety of natural water matrices. The observed first‐order photodegradation rate coefficient of the logarithmic‐transformed dissolved PbTx‐2 concentrations vs. irradiation time was 0.20 ± 0.04 h−1 in coastal seawater, corresponding to a half‐life of approximately 3 h based on 10 separate photolysis experiments. No loss of PbTx‐2 occurred in dark controls, indicating that this was primarily a photo‐mediated process. Photodegradation rate coefficients in samples in which dissolved organic matter was removed by ultraviolet oxidation prior to photolysis resulted in significantly slower rates of PbTx‐2 photodegradation (0.08 ± 0.03 h−1). When trace metals were also removed prior to photolysis, no loss of PbTx‐2 occurred, indicating that direct photolytic loss of PbTx‐2 is insignificant in coastal seawater. The proposed mechanism of PbTx‐2 decay is a photosensitized pathway involving organic matter and trace metals that is significantly accelerated by decreasing oxygen concentrations. The influence of molecular oxygen on the rate of toxin loss has important ramifications for the fate of PbTx‐2 during Karenia brevis blooms, as in situ dissolved O2 concentrations fluctuate widely during bloom development and decay. Sunlight‐mediated reactions are therefore a significant, yet previously unrecognized, sink of dissolved PbTx‐2 in seawater under environmentally relevant conditions.
Variations in the optical properties of a particle suspension associated with viral infection of marine bacteria
Authors: Uitz Julia , Stramski Dariusz , Baudoux Anne-Claire , Reynolds Rick A. , Wright Vanessa M. , Dubranna Jean , Azam Farooq
Published: September 2010

A laboratory experiment was conducted to examine the temporal dynamics of the particle size distribution (PSD) and associated optical variability caused by viral infection of marine heterotrophic bacteria. The PSD covering a broad range of particle size from ≈ 50 nm to 200 µm was measured in parallel with the spectral particulate absorption and beam attenuation coefficients, from which the particulate scattering coefficient, bp(λ), was determined. Within 12 h following infection, the host bacterial population collapsed, viral abundance increased, and submicron particles were produced as bacteria were disrupted and cell debris released, resulting in a large decrease in bp(λ) seen as an almost complete clearing of the particle suspension. Throughout the remainder of the experiment, significant changes in the PSD occurred primarily within the size range of relatively large particles (> 4 µm), likely as a result of the aggregation of smaller‐sized particles originating from the host lysis. The PSD data were used as input for Mie scattering calculations to evaluate the effects of these particle dynamics in terms of relative contributions of different particle size classes to the scattering and backscattering coefficients. This analysis showed a significant increase in the effect of particle aggregation on light scattering during the second and third days after infection. Viral lysis of bacteria and subsequent particle dynamics produce large variations in the PSD over a broad size range on timescales from hours to a few days, and such processes lead to correspondingly large changes in the suspension optical properties.
Degree of oligotrophy controls the response of microbial plankton to Saharan dust
Authors: Marañén Emilio , Fernández Ana , Mouriño-Carballido Beatriz , MartÍnez-GarcÍa Sandra , Teira Eva , Cermeño Pedro , Chouciño Paloma , Huete-Ortega MarÍa , Fernández Emilio , Calvo-DÍaz Alejandra , Morán Xosé Anxelu G. , Bode Antonio , Moreno-Ostos Enrique , Varela Marta M. , Patey Matthew D. , Achterberg Eric P.
Published: September 2010

To determine the effects of Saharan dust on the abundance, biomass, community structure, and metabolic activity of oceanic microbial plankton, we conducted eight bioassay experiments between ca. 30°N and 30°S in the central Atlantic Ocean. We found that, although bulk abundance and biomass tended to remain unchanged, different groups of phytoplankton and bacterioplankton responded differently to Saharan dust addition. The predominant type of metabolic response depended on the ecosystem's degree of oligotrophy and was modulated by competition for nutrients between phytoplankton and heterotrophic bacteria. The relative increase in bacterial production, which was the dominant response to dust addition in ultraoligotrophic environments, became larger with increasing oligotrophy. In contrast, primary production, which was stimulated only in the least oligotrophic waters, became less responsive to dust as the ecosystem's degree of oligotrophy increased. Given the divergent consequences of a predominantly bacterial vs. phytoplanktonic response, dust inputs can, depending on the ecosystem's degree of oligotrophy, stimulate or weaken biological CO2 drawdown. Thus, the biogeochemical implications of changing dust fluxes might not be universal, but variable through both space and time.
Aerosol mass and black carbon concentrations, a two year record at NCO-P (5079 m, Southern Himalayas)
Authors: Marinoni A. , Cristofanelli P. , Laj P. , Duchi R. , Calzolari F. , Decesari S. , Sellegri K. , Vuillermoz E. , Verza G. P. , Villani P. , Bonasoni P.
Published: September 2010

Abstract. Aerosol mass and the absorbing fraction are important variables, needed to constrain the role of atmospheric particles in the Earth radiation budget, both directly and indirectly through CCN activation. In particular, their monitoring in remote areas and mountain sites is essential for determining source regions, elucidating the mechanisms of long range transport of anthropogenic pollutants, and validating regional and global models. Since March 2006, aerosol mass and black carbon concentration have been monitored at the Nepal Climate Observatory-Pyramid, a permanent high-altitude research station located in the Khumbu valley at 5079 m a.s.l. below Mt. Everest. The first two-year averages of PM1 and PM1−10 mass were 1.94 μg m−3 and 1.88 μg m−3, with standard deviations of 3.90 μg m−3 and 4.45 μg m−3, respectively, while the black carbon concentration average is 160.5 ng m−3, with a standard deviation of 296.1 ng m−3. Both aerosol mass and black carbon show well defined annual cycles, with a maximum during the pre-monsoon season and a minimum during the monsoon. They also display a typical diurnal cycle during all the seasons, with the lowest particle concentration recorded during the night, and a considerable increase during the afternoon, revealing the major role played by thermal winds in influencing the behaviour of atmospheric compounds over the high Himalayas. The aerosol concentration is subject to high variability: in fact, as well as frequent "background conditions" (55% of the time) when BC concentrations are mainly below 100 ng m−3, concentrations up to 5 μg m−3 are reached during some episodes (a few days every year) in the pre-monsoon seasons. The variability of PM and BC is the result of both short-term changes due to thermal wind development in the valley, and long-range transport/synoptic circulation. At NCO-P, higher concentrations of PM1 and BC are mostly associated with regional circulation and westerly air masses from the Middle East, while the strongest contributions of mineral dust arrive from the Middle East and regional circulation, with a special contribution from North Africa and South-West Arabian Peninsula in post-monsoon and winter season.
Stability of temperatures from TIMED/SABER v1.07 (2002–2009) and Aura/MLS v2.2 (2004–2009) compared with OH(6-2) temperatures observed at Davis Station, Antarctica
Authors: French W. J. R. , Mulligan F. J.
Published: September 2010

Abstract. Temperature profiles from two satellite instruments – TIMED/SABER and Aura/MLS – have been used to calculate hydroxyl-layer equivalent temperatures for comparison with values measured from OH(6-2) emission lines observed by a ground-based spectrometer located at Davis Station, Antarctica (68° S, 78° E). The profile selection criteria – <500 km from the ground station and solar zenith angles >97° – yielded a total of 2359 SABER profiles over 8 years (2002–2009) and 7407 MLS profiles over 5.5 years (2004–2009). The availability of simultaneous OH volume emission rate (VER) profiles from the SABER (OH-B channel) enabled an assessment of the impact of several different weighting functions in the calculation of OH-equivalent temperatures. The maximum difference between all derived hydroxyl layer equivalent temperatures was less than 3 K. Restricting the miss-distance and miss-time criteria showed little effect on the bias, suggesting that the OH layer is relatively uniform over the spatial and temporal scales considered. However, a significant trend was found in the bias between SABER and Davis OH of ~0.7 K/year over the 8-year period with SABER becoming warmer compared with the Davis OH temperatures. In contrast, Aura MLS exhibited a cold bias of 9.9 ± 0.4 K compared with Davis OH, but importantly, the bias remained constant over the 2004–2009 year period examined. The difference in bias behaviour of the two satellites has significant implications for multi-annual and long-term studies using their data.
Evaluation of three different regional climate change scenarios for the application of a water balance model in a mesoscale catchment in Northeast Germany
Authors: Wegehenkel M. , Heinrich U. , Jochheim H. , Kersebaum K. C. , Röber B.
Published: September 2010

Abstract. Future climate changes might have some impacts on catchment hydrology. An assessment of such impacts on e.g. ground water recharge is required to derive adaptation strategies for future water resources management. The main objective of our study was an analysis of three different regional climate change scenarios for a catchment with an area of 2415 km2 located in the Northeastern German lowlands. These data sets consist of the STAR-scenario with a time period 1951–2055, the WettReg-scenario covering the period 1961–2100 and the grid based REMO-scenario for the time span 1950–2100. All three data sets are based on the SRES scenario A1B of the IPCC. In our analysis, we compared the meteorological data for the control period obtained from the regional climate change scenarios with corresponding data measured at meteorological stations in the catchment. The results of this analysis indicated, that there are high differences between the different regional climate change scenarios regarding the temporal dynamics and the amount of precipitation. In addition, we applied a water balance model using input data obtained from the different climate change scenarios and analyzed the impact of these different input data on the model output groundwater recharge. The results of our study indicated, that these regional climate change scenarios due to the uncertainties in the projections of precipitation show only a limited suitability for hydrologic impact analysis used for the establishment of future concrete water management procedures in their present state.
A comparison of light backscattering and particle size distribution measurements in tropical cirrus clouds
Authors: Cairo F. , Di Donfrancesco G. , Snels M. , Fierli F. , Viterbini M. , Borrmann S. , Frey W.
Published: September 2010

Abstract. An FSSP-100 Optical Particle Counter designed to count and size particles in the micron range and a backscattersonde that measures in-situ particle optical properties such as backscatter and depolarization ratio, are part of the payload of the high altitude research aircraft M55 Geophysica. This aircraft was deployed in tropical field campaigns in Bauru, Brasil (TROCCINOX, 2004) Darwin, Australia (SCOUT-Darwin, 2005) and Ouagadougou, Burkina Faso (SCOUT-AMMA, 2006). In those occasions, measurements of particle size distributions and optical properties within cirrus cloud were performed. Scope of the present work is to assess and discuss the consistency between the particle volume backscatter coefficient observed by the backscattersonde and the same parameter retrieved by optical scattering theory applied to particle size distributions as measured by the FSSP-100. In addition, empirical relationships linking the optical properties measured in-situ by the backscattersonde, which generally can be obtained by remote sensing techniques (LIDAR), and microphysical bulk properties like total particle number, surface and volume density will be presented and discussed.
A geostatistical synthesis study of factors affecting gross primary productivity in various ecosystems of North America
Authors: Yadav V. , Mueller K. L. , Dragoni D. , Michalak A. M.
Published: September 2010

Abstract. A coupled Bayesian model selection and geostatistical regression modeling approach is adopted for empirical analysis of gross primary productivity (GPP) at six AmeriFlux sites, including the Kennedy Space Center Scrub Oak, Vaira Ranch, Tonzi Ranch, Blodgett Forest, Morgan Monroe State Forest, and Harvard Forest sites. The analysis is performed at a continuum of temporal scales ranging from daily to monthly, for a period of seven years. A total of 10 covariates representing environmental stimuli and indices of plant physiology are considered in explaining variations in GPP. Similarly to other statistical methods, the presented approach estimates regression coefficients and uncertainties associated with the covariates in a selected regression model. Unlike traditional regression methods, however, the approach also estimates the uncertainty associated with the selection of a single "best" model of GPP. In addition, the approach provides an enhanced understanding of how the importance of specific covariates changes with the examined timescale (i.e. temporal resolution). An examination of changes in the importance of specific covariates across timescales reveals thresholds above or below which covariates become important in explaining GPP. Results indicate that most sites (especially those with a stronger seasonal cycle) exhibit at least one prominent scaling threshold between the daily and 20-day temporal scales. This demonstrates that environmental variables that explain GPP at synoptic scales are different from those that capture its seasonality. At shorter time scales, radiation, temperature, and vapor pressure deficit exert the most significant influence on GPP at most examined sites. At coarser time scales, however, the importance of these covariates in explaining GPP declines. Overall, unique best models are identified at most sites at the daily scale, whereas multiple competing models are identified at longer time scales.
Spatial and temporal patterns of CH4 and N2O fluxes in terrestrial ecosystems of North America during 1979–2008: application of a global biogeochemistry model
Authors: Tian H. , Xu X. , Liu M. , Ren W. , Zhang C. , Chen G. , Lu C.
Published: September 2010

Abstract. Continental-scale estimations of terrestrial methane (CH4) and nitrous oxide (N2O) fluxes over a long time period are crucial to accurately assess the global balance of greenhouse gases and enhance our understanding and prediction of global climate change and terrestrial ecosystem feedbacks. Using a process-based global biogeochemical model, the Dynamic Land Ecosystem Model (DLEM), we quantified simultaneously CH4 and N2O fluxes in North America's terrestrial ecosystems from 1979 to 2008. During the past 30 years, approximately 14.69 ± 1.64 T g C a−1 (1 T g = 1012 g) of CH4, and 1.94 ± 0.1 T g N a−1 of N2O were released from terrestrial ecosystems in North America. At the country level, both the US and Canada acted as CH4 sources to the atmosphere, but Mexico mainly oxidized and consumed CH4 from the atmosphere. Wetlands in North America contributed predominantly to the regional CH4 source, while all other ecosystems acted as sinks for atmospheric CH4, of which forests accounted for 36.8%. Regarding N2O emission in North America, the US, Canada, and Mexico contributed 56.19%, 18.23%, and 25.58%, respectively, to the continental source over the past 30 years. Forests and croplands were the two ecosystems that contributed most to continental N2O emission. The inter-annual variations of CH4 and N2O fluxes in North America were mainly attributed to year-to-year climatic variability. While only annual precipitation was found to have a significant effect on annual CH4 flux, both mean annual temperature and annual precipitation were significantly correlated to annual N2O flux. The regional estimates and spatiotemporal patterns of terrestrial ecosystem CH4 and N2O fluxes in North America generated in this study provide useful information for global change research and policy making.
Remote sensing of ecosystem light use efficiency with MODIS-based PRI – the DOs and DON'Ts
Authors: Goerner A. , Reichstein M. , Tomelleri E. , Hanan N. , Rambal S. , Papale D. , Dragoni D. , Schmullius C.
Published: September 2010

Abstract. Several studies sustained the possibility that a photochemical reflectance index (PRI) directly obtained from satellite data can be used as a proxy for ecosystem light use efficiency (LUE) in diagnostic models of gross primary productivity. This modelling approach would avoid the complications that are involved in using meteorological data as constraints for a fixed maximum LUE. However, no unifying model predicting LUE across climate zones and time based on MODIS PRI has been published to date. In this study, we evaluate the efficiency with which MODIS-based PRI can be used to estimate ecosystem light use efficiency at study sites of different plant functional types and vegetation densities. Our objective is to examine if known limitations such as dependance on viewing and illumination geometry can be overcome and a single PRI-based model of LUE (i.e. based on the same reference band) can be applied under a wide range of conditions. Furthermore, we were interested in the effect of using different faPAR (fraction of absorbed photosynthetically active radiation) products on the in-situ LUE used as ground truth and thus on the whole evaluation exercise. We found that estimating LUE at site-level based on PRI reduces uncertainty compared to the approaches relying on a maximum LUE reduced by minimum temperature and vapour pressure deficit. Despite the advantages of using PRI to estimate LUE at site-level, we could not establish an universally applicable light use efficiency model based on MODIS PRI. Models that were optimised for a pool of data from several sites did not perform well.