bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects and clinical significance of tetrahydrobiopterin supplementation in phenylalanine hydroxylase‐deficient hyperphenylalaninaemia
Authors: Gramer G. , Burgard P. , Garbade S. F. , Lindner M.
Published: August 2007

In recent years several studies on tetrahydrobiopterin (BH4)‐responsive phenylalanine hydroxylase (PAH) deficiency have been published. The molecular mechanisms of BH4 responsiveness are not conclusively understood, but there is evidence that BH4 responsiveness in hyperphenylalaninaemia (HPA) depends on the patient's genotype and residual PAH activity. As a BH4 preparation will soon obtain marketing approval as an alternative treatment for phenylketonuria (PKU), it is particularly important to evaluate this treatment and to define criteria to identify patients with a potential benefit from it. Most of the patients found to be BH4‐responsive suffered from mild PKU or mild hyperphenylalaninaemia (MHP) and some of these would not be treated at all in many countries. Of patients with moderate and classic forms of PKU, only a few were classified as responders and the clinical significance of the effect size may be small.
Sensitivity of MRQAP Tests to Collinearity and Autocorrelation Conditions
Authors: Dekker David , Krackhardt David , Snijders Tom A. B.
Published: August 2007

Multiple regression quadratic assignment procedures (MRQAP) tests are permutation tests for multiple linear regression model coefficients for data organized in square matrices of relatedness among n objects. Such a data structure is typical in social network studies, where variables indicate some type of relation between a given set of actors. We present a new permutation method (called “double semi-partialing”, or DSP) that complements the family of extant approaches to MRQAP tests. We assess the statistical bias (type I error rate) and statistical power of the set of five methods, including DSP, across a variety of conditions of network autocorrelation, of spuriousness (size of confounder effect), and of skewness in the data. These conditions are explored across three assumed data distributions: normal, gamma, and negative binomial. We find that the Freedman–Lane method and the DSP method are the most robust against a wide array of these conditions. We also find that all five methods perform better if the test statistic is pivotal. Finally, we find limitations of usefulness for MRQAP tests: All tests degrade under simultaneous conditions of extreme skewness and high spuriousness for gamma and negative binomial distributions.
Does Thumb Immobilization Contribute to Scaphoid Fracture Stability?
Authors: Schramm J. Mark , Wongworawat Montri D. , Nguyen Minhthy , Kjellin Ingrid
Published: August 2007

Immobilization protocols for nondisplaced scaphoid fractures have included the elbow, wrist, and thumb. This study attempts to demonstrate whether or not immobilization of the thumb makes a difference in preventing motion at the scaphoid fracture site. Using six fresh frozen forearm specimens, a transverse waist scaphoid fracture was created through a dorsal approach. Metallic markers were imbedded on either side of the fracture. Sutures were secured to the flexor pollicus longus (FPL) and extensor pollicus longus (EPL). Each specimen was loaded in extension and flexion by attaching 50-g weights to the EPL and FPL, first with no casting, then with a short arm cast, and finally a short arm thumb spica cast. Angulation and displacement at the fracture site were measured in the coronal, sagittal, and axial planes utilizing image reconstructions from computed tomography. One-way ANOVA with repeated measures and Tukey–Kramer multiple comparison test post hoc analysis were used for statistical evaluation. There was no significant difference in fracture angulation or rotation between spica and short arm casts. There was a significant difference in angulation and rotation in all three planes when comparing between casting and no casting, p<0.05. In our cadaveric model, wrist immobilization is crucial for nondisplaced scaphoid waist fractures, and short arm casting was just as effective as thumb spica casting in preventing fracture displacement.
CMC Arthroplasty of the Thumb: A Review
Authors: Matullo Kristofer S. , Ilyas Asif , Thoder Joseph J.
Published: August 2007

Arthritis of the first carpometacarpal (CMC) joint of the hand is a common and often debilitating disease. Diagnosis can be readily made with history, physical exam, and radiographic evaluation. Patients with advanced disease who have failed conservative treatment modalities have multiple surgical options including ligament reconstruction, resection arthroplasty, silicone implantation, tendon interposition, or total joint arthroplasty. This article will describe the variety of approaches to treatment as well as the author's preferred method.
Effect of Sterol Carrier Protein‐2 Expression on Sphingolipid Distribution in Plasma Membrane Lipid Rafts/Caveolae
Authors: Atshaves Barbara P. , Jefferson John R. , McIntosh Avery L. , Gallegos Adalberto , McCann Bonnie M. , Landrock Kerstin K. , Kier Ann B. , Schroeder Friedhelm
Published: August 2007

Although sphingolipids are highly important signaling molecules enriched in lipid rafts/caveolae, relatively little is known regarding factors such as sphingolipid binding proteins that may regulate the distribution of sphingolipids to lipid rafts/caveolae of living cells. Since early work demonstrated that sterol carrier protein‐2 (SCP‐2) enhanced glycosphingolipid transfer from membranes in vitro, the effect of SCP‐2 expression on sphingolipid distribution to lipid rafts/caveolae in living cells was examined. Using a non‐detergent affinity chromatography method to isolate lipid rafts/caveolae and non‐rafts from purified L‐cell plasma membranes, it was shown that lipid rafts/caveolae were highly enriched in multiple sphingolipid species including ceramides, acidic glycosphingolipids (ganglioside GM1); neutral glycosphingolipids (monohexosides, dihexosides, globosides), and sphingomyelin as compared to non‐raft domains. SCP‐2 overexpression further enriched the content of total sphingolipids and select sphingolipid species in the lipid rafts/caveolae domains. Analysis of fluorescence binding and displacement data revealed that purified human recombinant SCP‐2 exhibited high binding affinity (nanomolar range) for all sphingolipid classes tested. The binding affinity decreased in the following order: ceramides > acidic glycosphingolipid (ganglioside GM1) > neutral glycosphingolipid (monohexosides, hexosides, globosides) > sphingomyelin. Enrichment of individual sphingolipid classes to lipid rafts/caveolae versus non‐rafts in SCP‐2 expressing plasma membranes followed closely with those classes most strongly bound to SCP‐2 (ceramides, GM1 > the neutral glycosphingolipids (monohexosides, dihexosides, and globosides) > sphingomyelin). Taken together these data suggested that SCP‐2 acts to selectively regulate sphingolipid distribution to lipid rafts/caveolae in living cells.
The Effects of Simultaneous Administration of Dietary Conjugated Linoleic Acid and Telmisartan on Cardiovascular Risks in Rats
Authors: Abdullah Mohammad M. , Xu Zuyuan , Pierce Grant N. , Moghadasian Mohammed H.
Published: August 2007

Dietary conjugated linoleic acid (CLA) and the antihypertensive drug, telmisartan, have both been shown to modify cardiovascular risks. The effects of a combination of these two agents have, however, not been investigated. This 20 week study sought to assess the therapeutic potential of a CLA/telmisartan co‐administration in rats fed a high‐fructose high‐fat diet. Thirty‐three male Sprague–Dawley rats were randomly assigned to five experimental groups, including control, losartan, telmisartan, CLA, and CLA + telmisartan‐treated animals. Body weight, blood pressure, and blood levels of lipids, glucose, insulin, and inflammatory markers were measured. Co‐administration of CLA and telmisartan resulted in significant (P < 0.05) reductions in body weight, visceral fat, serum total cholesterol, triglycerides, glucose, plasma insulin concentrations, and systolic blood pressure compared with those in the control group. Moreover, plasma levels of IL1‐α and IFN‐γ were reduced and levels of IL1‐β, IL‐4, IL‐6, and IL‐10, plus TNF‐α were increased in the co‐therapy group, compared with controls. In conclusion, this study suggests that a combination of CLA with telmisartan may modify several risk factors of cardiovascular disease commonly seen in metabolic syndrome. This combination of nutraceuticals and pharmaceuticals may be a safe and cost‐effective strategy in a number of high‐risk subjects. Future studies will further document clinical benefits of such combination therapy.
Dietary Virgin Olive Oil Reduces Oxidative Stress and Cellular Damage in Rat Brain Slices Subjected to Hypoxia–Reoxygenation
Authors: González‐Correa J. A. , Muñoz‐Marín J. , Arrebola M. M. , Guerrero A. , Narbona F. , López‐Villodres J. A. , De La Cruz J. P.
Published: August 2007

We investigated how virgin olive oil (VOO) affected platelet and hypoxic brain damage in rats. Rats were given VOO orally for 30 days at 0.25 or 0.5 mL kg−1 per day (doses A and B, respectively). Platelet aggregation, thromboxane B2, 6‐keto‐PGF1α, and nitrites + nitrates were measured, and hypoxic damage was evaluated in a hypoxia–reoxygenation assay with fresh brain slices. Oxidative stress, prostaglandin E2, nitric oxide pathway activity and lactate dehydrogenase (LDH) activity were also measured. Dose A inhibited platelet aggregation by 36% and thromboxane B2 by 19%; inhibition by dose B was 47 and 23%, respectively. Virgin olive oil inhibited the reoxygenation‐induced increase in lipid peroxidation (57% in control rats vs. 2.5% (P < 0.05) in treated rats), and reduced the decrease in glutathione concentration from 67 to 24% (dose A) and 41% (dose B). Brain prostaglandin E2 after reoxygenation was 306% higher in control animals, but the increases in treated rats were only 53% (dose A) and 45% (dose B). The increases in nitric oxide production (213% in controls) and activity of the inducible isoform of nitric oxide synthase (175% in controls) were both smaller in animals given VOO (dose A 84%; dose B 12%). Lactate dehydrogenase activity was reduced by 17% (dose A) and 42% (dose B). In conclusion, VOO modified processes related to thrombogenesis and brain ischemia. It reduced oxidative stress and modulated the inducible isoform of nitric oxide synthase, diminishing platelet aggregation and protecting the brain from the effects of hypoxia–reoxygenation.
Effect of Dietary Cholesterol and Fat on Cell Cholesterol Transfer to Postprandial Plasma in Hyperlipidemic Men
Authors: Sutherland Wayne H. F. , de Jong Sylvia A. , Walker Robert J.
Published: August 2007

Postprandial chylomicrons are potent ultimate acceptors of cell membrane cholesterol and are believed to accelerate reverse cholesterol transport (RCT). We compared the effects of meals rich in polyunsaturated fat (PUFA) and either high (605 mg) or low (151 mg) in cholesterol and a meal rich in dairy fat (DF) in the form of cream on net in vitro transport of red blood cell (RBC) membrane cholesterol to 4 and 6 h postprandial plasma in eight normotriglyceridemic (NTG‐H) and eight hypertriglyceridemic (HTG‐H) men with mild to moderate hypercholesterolemia. In HTG‐H men, cell cholesterol accumulation in 6‐h postprandial plasma was significantly (P = 0.02) less after the PUFA‐HC meal compared with the other meals. The significant (P < 0.001) increase in cell plus endogenous cholesterol accumulation in the triglyceride‐rich lipoprotein (TRL) fraction of 4 h postprandial plasma incubated with RBC was significantly (P = 0.007) higher after the PUFA‐HC meal compared with DF meal in HTG‐H men. In NTG‐H men, cholesterol accumulation in plasma and plasma lipoproteins in the presence and absence of RBC was not significantly affected by the type of meal ingested. These data suggest that addition of large amounts of cholesterol to a PUFA meal may impair diffusion‐mediated transport of cell membrane cholesterol to postprandial plasma and that replacing DF with PUFA in a meal increases postprandial lipemia and may potentially increase cholesterol accumulation in atherogenic postprandial TRL in HTG‐H men.
Effect of Ultrasonication on Droplet Size in Biodiesel Mixtures
Authors: Wu Peng , Yang Ying , Colucci José A. , Grulke Eric A.
Published: August 2007

Biodiesel fuels have become more attractive recently because of their environmental benefits and cost competitiveness compared to diesel fuel. Many processing improvements have been proposed to increase the conversion rates and the yields of vegetable oil in order to lower production costs and improve biodiesel product quality. In conventional biodiesel production chemistries, alkaline transesterifications of alcohol/oil dispersions should occur primarily near the interface. Ultrasonic mixing has already been shown to increase overall conversion rates for alcohol/vegetable oil mixtures. Our data show that ultrasonic mixing produced smaller droplet sizes than conventional agitation, leading to more interfacial area for the reaction to occur. Droplet size distributions have been measured for conventional impeller and ultrasonic mixing systems using methanol/soybean oil as a model system. The dispersions were stabilized by surfactant in order to obtain droplet size distribution for mixture samples. Ultrasonic mixing produced dispersions with average droplet sizes 42% smaller than those generated using standard impellers.
Job Displacement and Reemployment in North Carolina: The Relative Experience of the Black Worker
Authors: Field Alfred J. , Winfrey William R.
Published: August 2007

This article examines the unemployment experiences of workers in North Carolina involved in mass layoffs and plant closings, focusing on the differential impacts between black and white workers. The results of this research not only support earlier findings but also suggest that blacks are laid off in numbers disproportionate to their membership in the labor force. Several different explanations for this result are examined and attempts made to control for several of these factors, such as industry and occupational differences. However, even after controlling for such factors, evidence of differential treatment continues to persist.
Racial Differences in the Hurdling of Prenatal Care Barriers
Authors: Warner Geoffrey
Published: August 2007

The success of black or white mothers in obtaining adequate prenatal care is examined. Two departures from public health convention are employed. The independent variables’ marginal effects are calculated from their logit coefficients. The odds ratio of care adequacy between races is derived from race-specific regressions. It yields a smaller variance and type II decision error likelihood compared to the race dummy method.

A working-class life outlook and apathetic fathers are the highest barriers to adequate care. Wantedness, in the form of desired timing, is a very strong motivator. Improving upward socioeconomic mobility and paternal attitudes are important aspects of increasing prenatal care adequacy rates.
Distributed team design in small- and medium-sized enterprises: How to get it right
Authors: Thomson Avril , Stone Angela , Ion William
Published: August 2007

Readily available and affordable technologies such as the Internet, groupware, and Web conferencing mean that sharing information and data within teams is simple and affordable. However, many small- and medium-sized enterprises (SMEs) struggle to implement or perform distributed collaborative design effectively or even at all. As part of the extended design team of large multinational companies it is not uncommon for SMEs to have collaborative working tools and practice imposed on them to meet the requirements of the multinational. However, many SMEs need to develop their own working practices to support effective, collaborative team design within their own organization or their extended design team. Through a series of case studies, this paper describes how a typical SME achieved successful distributed team design within their organization. A “strategy for effective distributed team design” encompassing the processes, methods, and tools developed and implemented within the company to achieve this success, is presented. In total, four live case studies, spanning a 2-year period, are described; two initial studies focus on current distributed design team practice clearly highlighting issues and areas for improvement, leading to the development of processes, methods, and tools to support distributed collaborative team design. A strategy for effective distributed team design encapsulating these processes methods and tools is presented together with its evaluation through two further live industrial case studies. The case studies themselves, together with the processes, methods, and tools developed by this company, could be adopted by other SMEs directly to achieve the same success. Generic and transferable findings drawn from this study aimed at helping others achieve this success form the conclusion of the paper.
Agents for multidisciplinary design in virtual worlds
Authors: Maher Mary Lou , Rosenman Michael , Merrick Kathryn
Published: August 2007

Agent models provide a generalized approach to the design of systems that autonomously monitor and affect an environment. Societies of agents that reason and communicate about an environment can achieve complex emergent behavior to facilitate and augment human activities. This paper introduces artificial agent technologies as a means by which the behavioral complexity of virtual worlds can be extended to provide the functionality needed to support collaboration in multidisciplinary design teams. Three key roles are identified that artificial agents can play to provide this functionality: support for multiple views of designed objects, support for the expression of relationships between designed objects, and compatibility with existing design tools. The implementation of a society of agents fulfilling these roles within a virtual world based, multidisciplinary design tool called DesignWorld is described. The increased behavioral complexity and functionality of DesignWorld's underlying virtual world is demonstrated using the results of multidisciplinary design experiments with DesignWorld.
On the Laplacian Eigenvalues of Gn,p
Authors: COJA-OGHLAN AMIN
Published: August 2007

We investigate the Laplacian eigenvalues of sparse random graphs Gnp. We show that in the case that the expected degree d = (n-1)p is bounded, the spectral gap of the normalized Laplacian $\LL(\gnp)$ is o(1). Nonetheless, w.h.p. G = Gnp has a large subgraph core(G) such that the spectral gap of $\LL(\core(G))$ is as large as 1-O (d−1/2). We derive similar results regarding the spectrum of the combinatorial Laplacian L(Gnp). The present paper complements the work of Chung, Lu and Vu [8] on the Laplacian spectra of random graphs with given expected degree sequences. Applied to Gnp, their results imply that in the ‘dense’ case d ≥ ln2n the spectral gap of $\LL(\gnp)$ is 1-O (d−1/2) w.h.p.
A congenital fistula between the descending aorta and the right pulmonary vein in a neonate presenting with heart failure
Authors: Shebani Suhair O. , Khan Mohammad D. , Tofeig Magdi A.
Published: August 2007

We report a large congenital fistula connecting the descending thoracic aorta to the right upper pulmonary vein in a newborn baby presenting on the seventh day of life with cardiac failure and a continuous murmur heard posteriorly. The fistula was detected echocardiographically, and shown at cardiac catheterisation not to be suitable for percutaneous occlusion. The anatomy of the fistula was confirmed at surgery, when it was ligated successfully.
Linear tabling strategies and optimizations
Authors: ZHOU NENG-FA , SATO TAISUKE , SHEN YI-DONG
Published: August 2007

Recently there has been a growing interest in research in tabling in the logic programming community because of its usefulness in a variety of application domains including program analysis, parsing, deductive databases, theorem proving, model checking, and logic-based probabilistic learning. The main idea of tabling is to memorize the answers to some subgoals and use the answers to resolve subsequent variant subgoals. Early resolution mechanisms proposed for tabling such as OLDT and SLG rely on suspension and resumption of subgoals to compute fixpoints. Recently, the iterative approach named linear tabling has received considerable attention because of its simplicity, ease of implementation, and good space efficiency. Linear tabling is a framework from which different methods can be derived on the basis of the strategies used in handling looping subgoals. One decision concerns when answers are consumed and returned. This article describes two strategies, namely,lazyandeagerstrategies, and compares them both qualitatively and quantitatively. The results indicate that, while the lazy strategy has good locality and is well suited for finding all solutions, the eager strategy is comparable in speed with the lazy strategy and is well suited for programs with cuts. Linear tabling relies on depth-first iterative deepening rather than suspension to compute fixpoints. Each cluster of interdependent subgoals as represented by a topmost looping subgoal is iteratively evaluated until no subgoal in it can produce any new answers. Naive re-evaluation of all looping subgoals, albeit simple, may be computationally unacceptable. In this article, we also introduce semi-naive optimization, an effective technique employed in bottom-up evaluation of logic programs to avoid redundant joins of answers, into linear tabling. We give the conditions for the technique to be safe (i.e., sound and complete) and propose an optimization technique calledearly answer promotionto enhance its effectiveness. Benchmarking in B-Prolog demonstrates that with this optimization linear tabling compares favorably well in speed with the state-of-the-art implementation of SLG.
Continuous quasiperiodic thermospheric waves over Arecibo
Authors: Livneh D. J. , Seker I. , Djuth F. T. , Mathews J. D.
Published: August 2007

Incoherent scatter radar (ISR) power profile observations at Arecibo Observatory (AO) have revealed long vertical wavelength (>100 km) quasi‐coherent waves with periods of ∼1 hour that are observed to be nearly continuously present over two ∼35‐hour geomagnetically quiet observation periods. When properly filtered, results from both 22–23 March 2004 and 5–6 June 2005 provide unambiguous views of these waves. The waves are strong throughout the F region, often spanning 160 to above 500 km in altitude and are present day and night in the F2 layer. Filtering techniques that were used to better reveal the waves are extensively discussed. Barometric pressure and imager data, both of which were taken on site at Arecibo, are used to provide further insight into the nature of these waves. These waves may be linked to high‐latitude medium‐scale traveling ionospheric disturbances (MSTIDs) observed with the superDARN radar network and associated with E region auroral electrojet source(s) that are quasi‐coherent under geomagnetic quiet conditions. As auroral‐zone MSTIDs are believed to dissipate before reaching Arecibo latitudes (Vadas, 2007), various alternative sources including weather patterns are explored.
Complex seismic anisotropy in the top of the Earth's inner core beneath Africa
Authors: Yu Wen‐che , Wen Lianxing
Published: August 2007

We report complex seismic anisotropy in the top 80 km of the Earth's inner core beneath Africa. The anisotropy in the top 80 km of the inner core is constrained using differential travel times, amplitude ratios, and waveforms of the PKiKP‐PKIKP phases sampling Africa along various directions. The differential PKiKP‐PKIKP time residuals (relative to the Preliminary Reference Earth Model [PREM]) along the polar paths are larger than those along the equatorial paths by 0–1.4 s, indicating the presence of seismic anisotropy in the top 80 km of the inner core. Furthermore, the observations along the polar paths show complex regional variations beneath Africa: the differential PKiKP‐PKIKP travel time residuals vary from 1.2 s beneath eastern Africa, to −0.1 s beneath central Africa, and to −0.2 to 0.8 s beneath western Africa. A correlation between small PKIKP/PKiKP amplitude ratios and large differential PKiKP‐PKIKP travel time residuals is observed. The waveform data are spatially binned into six groups to constrain the regional dependence of velocity and attenuation anisotropy in the top 80 km of the inner core. Overall, the seismic data can be explained by an isotropic upper inner core (UIC) overlying an anisotropic lower inner core (LIC) in the top 80 km of the inner core across Africa. The thickness of the isotropic UIC varies from 0 to 50 km, and the P velocity transition from the isotropic UIC to the anisotropic LIC is sharp, with velocity increases laterally varying from 1.6% to 2.2%. The attenuation structure along the polar paths has a Q value of 600 for the isotropic UIC and Q values varying from 150 to 400 for the anisotropic LIC. The complex seismic anisotropy in the top of the inner core is found in a region where a rapid change of the inner core boundary (ICB) between 1993 and 2003 was discovered (Wen, 2006) and may be explained by complex alignments of iron crystals, resulting from a localized anomalous solidification of the inner core.
Assessment of noise in GPS coordinate time series: Methodology and results
Authors: Amiri‐Simkooei A. R. , Tiberius C. C. J. M. , Teunissen P. J. G.
Published: August 2007

We propose a methodology to assess the noise characteristics in time series of position estimates for permanent Global Positioning System (GPS) stations. Least squares variance component estimation (LS‐VCE) is adopted to cope with any type of noise in the data. LS‐VCE inherently provides the precision of (co)variance estimators. One can also apply statistical hypothesis testing in conjunction with LS‐VCE. Using thew‐test statistic, a combination of white noise and flicker noise turns out in general to best characterize the noise in all three position components. An interpretation for the colored noise of the series is given. Unmodelled periodic effects in the data will be captured by a set of harmonic functions for which we rely on the least squares harmonic estimation (LS‐HE) method and parameter significance testing developed in the same framework as LS‐VCE. Having included harmonic functions into the model, practically only white noise can be shown to remain in the data. Remaining time correlation, present only at very high frequencies (spanning a few days only), is expressed as a first‐order autoregressive noise process. It can be caused by common and well‐known sources of errors like atmospheric effects as well as satellite orbit errors. The autoregressive noise should be included in the stochastic model to avoid the overestimation (upward bias) of power law noise. The results confirm the presence of annual and semiannual signals in the series. We observed also significant periodic patterns with periods of 350 days and its fractions 350/n,n= 2, …, 8 that resemble the repeat time of the GPS constellation. Neglecting these harmonic signals in the functional model can seriously overestimate the rate uncertainty.
Wind speed influence on phytoplankton bloom dynamics in the Southern Ocean Marginal Ice Zone
Authors: Fitch Dillon T. , Moore J. Keith
Published: August 2007

Analysis of satellite ocean color and wind speed data within the seasonal ice zone (SIZ) of the Southern Ocean sheds light on the physical processes that influence phytoplankton biomass distributions. A compilation of monthly averaged chlorophyll and percent sea ice cover data within the SIZ from 1997 to 2005 has been compared with monthly average wind speed data from 1999 to 2005. The size of the marginal ice zone (MIZ, areas of recent ice retreat) was fairly consistent from year to year, always peaking in December, with a mean area of 6.0 million km2. The mean area within the MIZ with phytoplankton blooms (chlorophyll exceeding 0.8 mg/m3) was 0.36 million km2. While the bloom areal extent seems small compared to the MIZ, in reality, because of gaps in the chlorophyll data, blooming regions comprise a much larger fraction of the MIZ. Considering only areas with valid chlorophyll data, the percentage of the MIZ with blooms was 17%, 21%, and 24% for the months of December, January, and February, respectively. December always has the largest MIZ area, but MIZ mean chlorophyll concentrations sometimes do not peak until February. Wind speed strongly impacts phytoplankton bloom dynamics within the MIZ. There is an inverse relation between wind speed and bloom occurrence, with blooms largely suppressed at high wind speeds. At low wind speeds (∼5 m/s), blooms are observed over about one third of the MIZ. Blooms are also much more frequent near the continent than in offshore waters, likely due to increased iron availability. Open ocean phytoplankton blooms in the Southern Ocean are likely to become iron‐light co‐limited except in regions where the mixed layer depth is relatively shallow.
Investigation of the first and second aerosol indirect effects using data from the May 2003 Intensive Operational Period at the Southern Great Plains
Authors: Guo Huan , Penner Joyce E. , Herzog Michael , Xie Shaocheng
Published: August 2007

The Active Tracer High‐Resolution Atmospheric Model is used to examine the aerosol indirect effect (AIE) for a spring continental stratus cloud on the basis of data collected during the 17 May 2003 Aerosol Intensive Operation Period (AIOP) at the Atmospheric Radiation Measurement (ARM) Program Southern Great Plains site. Model results for our base case, which uses observed aerosol concentrations, agree reasonably well with the available observations, giving confidence that the basic model is reasonable. Sensitivity tests are performed to explore the response of the clouds to changes in the aerosol number concentration and surface fluxes. During the major part of the simulation, from 0630 through 1400 local standard time (LST), an increase in the aerosol number concentration (Na) results in a decrease of the mean cloud droplet size and an increase of the cloud liquid water path (LWP) until aerosol number concentration levels reach 1200 cm−3. Further increases in aerosol concentration do not increase the liquid water path because the depletion of cloud water by precipitation is negligible above this number concentration. After 1400 LST, the liquid water path decreases when aerosols increase as long as Na < 600 cm−3 and remains unchanged for higher aerosol concentrations. The decrease of LWP is associated with the evaporative cooling below cloud base which leads to more condensation of water vapor, a result that is consistent with afternoon satellite observations of the response of continental clouds to increases in droplet concentrations. A sensitivity test with a stronger surface latent flux increases both the cloud geometrical thickness and cloud water content. On the other hand, a sensitivity test with a stronger surface sensible heat flux leads to a higher cloud base and a shallower and drier cloud. The response of the cloud geometrical thickness to changes in surface sensible heat flux dominates that of the cloud water content. The cloud fraction is also reduced at the end of the simulation time period. Because the surface heat fluxes will likely change when aerosol and droplet number concentrations change, these sensitivity tests show that a fully coupled simulation with a land surface model will be needed to fully assess the response of the cloud to changing aerosol concentrations. Nevertheless, since the thermodynamic boundary layer profiles do not change significantly when aerosol concentrations are changed, our results for changing aerosol concentrations are qualitatively correct.
Significant reduction of surface solar irradiance induced by aerosols in a suburban region in northeastern China
Authors: Xia Xiangao , Chen Hongbin , Li Zhanqing , Wang Pucai , Wang Jiankai
Published: August 2007

In the spring of 2005, a Sun photometer and a set of broadband pyranometers were installed in Liaozhong, a suburban region in northeastern China. Aerosol properties derived from Sun photometer measurements and aerosol‐induced changes in downwelling shortwave surface irradiances are analyzed in this paper. It is shown that the mean aerosol optical depth (AOD) at 500 nm is 0.63. The day‐to‐day variation of aerosol optical depth is dramatic, with a maximum daily AOD close to 2.0 and a minimum value close to the background level. Dust activities generally produce heavy aerosol loading characterized by larger particle sizes and less absorption than those observed under normal conditions. The reduction of instantaneous direct shortwave surface irradiance per unit of AOD is 404.5 W m−2. About 63.8% of this reduction is offset by an increase in diffuse irradiance; consequently, one unit increase in AOD leads to a decrease in global surface irradiance of 146.3 W m−2. The diurnal aerosol direct radiative forcing efficiency is about −47.4 W m−2. Overall, aerosols reduce about 30 W m−2 per day of surface net shortwave irradiance in this suburban region.
Dominant aerosol processes during high‐pollution episodes over Greater Tokyo
Authors: Sartelet K. N. , Hayami H. , Sportisse B.
Published: August 2007

This paper studies two high‐pollution episodes over Greater Tokyo: 9 and 10 December 1999 and 31 July and 1 August 2001. Results obtained with the chemistry transport model (CTM) Polair3D are compared to measurements of inorganic particulate matter (PM2.5). To understand to which extent the aerosol processes modeled in Polair3D impact simulated inorganic PM2.5, Polair3D is run with different options in the aerosol module, i.e., with/without heterogeneous reactions. To quantify the impact of processes outside the aerosol module, simulations are also done with another CTM (community multiscale air quality, CMAQ). In the winter episode, sulfate is mostly impacted by condensation, coagulation, long‐range transport, and deposition to a lesser extent. In the summer episode, the effect of long‐range transport largely dominates. The impact of condensation/evaporation is dominant for ammonium, nitrate, and chloride in both episodes. However, the impact of the thermodynamic equilibrium assumption is limited. The impact of heterogeneous reactions is large for nitrate and ammonium and, taking heterogeneous reactions into account, appears to be crucial in predicting the peaks of nitrate and ammonium. The impact of deposition is the same for all inorganic PM2.5. It is small compared to the impact of other processes although it is not negligible. The impact of nucleation is negligible in the summer episode and small in the winter episode. The impact of coagulation is larger in the winter episode than in the summer episode because the number of small particles is higher in the winter episode as a consequence of nucleation.
Spatiotemporal characteristics of photosynthetically active radiation in China
Authors: Hu Bo , Wang Yuesi , Liu Guangren
Published: August 2007

Photosynthetically active radiation (PAR) plays an important part in climate change and ecological processes. Few PAR measurements are usually available, especially in China. Thus it is important and significant to investigate the spatiotemporal characteristics of PAR in China for radiation budget and ecosystem studies. In order to study the spatiotemporal characteristics of PAR, photosynthetic photon flux density (Qp) and broadband solar radiation (Rs) measurement data were analyzed for the period of January 2005 to June 2006. Qp increases gradually from spring and reaches its maximum and minimum in summer and winter, respectively. The highest value of annual mean daily Qp (40.9 ± 4.1 mol m−2 d−1) appears in the Qinghai‐Tibet Plateau region, along with higher atmospheric transmission; and the lowest value (17.4 ± 9.03 mol m−2 d−1) is found in the northern subtropics, along with the largest aerosol optical depth (AOD) and a lower water vapor content. PAR fraction shows a similar seasonal trend as that of Qp at all sites except for some near to lakes and sea. The annual mean daily value of PAR fraction varies from 1.75 ± 0.12 to 2.3 ± 0.15 mol MJ−1 over China. The largest value appears in tropical regions because of higher relative humidity (RH). The lowest value is observed at the Luancheng site, which features low humidity and an abundance of fine aerosols, instead of sites in China's driest northern desert region. The variability of PAR fraction is mainly controlled by the selective scattering of aerosol particles and absorption of water vapor. Two different diurnal trends of PAR fraction are observed in China. In most sites, PAR fraction tends to peak during sunrise or sunset and reaches its lowest value around noon. However, it exhibits an opposite trend in the northern desert area because of the distinctive diurnal variation of water vapor in this region. Further analysis of annual mean hourly PAR fraction shows that the national average is 1.82 ± 0.11 and 2.00 ± 0.08 μmol J−1 for clear and cloudy days, respectively. The cloudy day's ratio is therefore 10% higher than that for clear days. The altitude dependency of PAR fraction is very weak below 1500 m because of uneven distributions of water vapor, clouds, and aerosols. Above 1500 m, PAR fraction increases gradually with altitude on both cloudy and clear days, attributed to the weaker extinction of Qp at higher‐altitude sites. The distribution pattern of annual mean daily PAR fraction is similar to that of the hourly value. Its magnitude is medial to the hourly values on cloudy and clear days. These results are helpful for understanding the climatic, agricultural, and ecological processes over China and useful for primary productivity estimation and ecosystem–atmosphere CO2 exchange study in China.
New parameterization of sulfuric acid‐ammonia‐water ternary nucleation rates at tropospheric conditions
Authors: Merikanto J. , Napari I. , Vehkamäki H. , Anttila T. , Kulmala M.
Published: August 2007

Recently, the classical theory of sulfuric acid‐ammonia‐water (H2SO4‐NH3‐H2O) nucleation was reinvestigated by including the effect of stable ammonium bisulfate formation into calculations. The predicted nucleation rates lowered by many orders of magnitude, bringing them close to agreement with the available experiments on H2SO4‐NH3‐H2O nucleation. However, because of complex thermodynamics involved, the theoretical calculations of nucleation rates are computationally demanding, and sometimes the theory breaks down at specific concentrations and temperatures. Here we present parameterized equations of ternary H2SO4‐NH3‐H2O nucleation rates, critical cluster sizes, and critical cluster compositions. Our parameterizations reduce the computing time of these values by a factor of 105 compared with the calculations with the full thermodynamic model. Also, our parameterizations provide reliable estimates for ternary nucleation rates in cases when the full theory fails in isolated points of the parameter space. The parameterized nucleation rates are accurate to one order of magnitude in nucleation rate. Because of their computational efficiency, our parameterizations are particularly suitable for large‐scale models of atmosphere. They are valid for temperatures above 235 K, sulfuric acid concentrations 5 · 104–109 cm−3, ammonia mixing ratios 0.1–1000 ppt, relative humidities 5%–95%, and nucleation rates over 10−5 cm−3 s−1. At these conditions, no significant nucleation occurs above 295 K.
Chemical composition and source characterization of spring aerosol over Horqin sand land in northeastern China
Authors: Shen Z. X. , Cao J. J. , Arimoto R. , Zhang R. J. , Jie D. M. , Liu S. X. , Zhu C. S.
Published: August 2007

In spring 2005, daily particulate matter (PM2.5) aerosol samples were collected at Tongliao, a site in the Horqin sand land of northeastern China. The concentrations of 20 elements, 9 water‐soluble ions, and elemental and organic carbon (EC and OC, respectively) were determined in the filter samples. Crustal material was the major contributor to the PM2.5 mass, but rural biomass burning and local urban pollution also influenced the composition of the aerosol. The mean PM2.5 mass concentration was 126 ± 71 μg m−3 (arithmetic mean ± standard deviation), with higher loadings during five dust storms (DS, 255 ± 80 μg m−3) than for normal days (ND, 104 ± 43 μg m−3) or pollution episodes (PE, 118 ± 52 μg m−3). During the DS, crustal material accounted for 69% of the PM2.5 mass, followed by carbonaceous matter (14%), sulfate (4%), nitrate (2%), ammonium (1%), and chloride (1%). The observed Si/Al, Ca/Al, and Fe/Al ratios during the DS events were different from those in dust from western or central/northern Asia. On normal days the percentage of crustal material decreased to 43%, and the mass of carbonaceous matter increased 2 times over that during DS. During the pollution episodes the contributions of sulfate and nitrate were 3 times those on DS while ammonium increased four‐fold. Secondary aerosols (NH4+, SO42−, and NO3−) were the dominant species during the pollution episodes, but SO42− and NO3− also were important components of the aerosol during DS events, suggesting that mineral dust was mixed with other materials. Ion balance calculations indicate that the DS samples were alkaline, the ND samples were weakly alkaline, and the PE samples were slightly acidic. A deficit of measured anions during DS implied the presence of carbonate; this evidently accounts for ∼5.5% of the PM2.5 mass. The average OC and EC concentrations were 16.3 ± 7.3 μg m−3 and 3.4 ± 1.7 μg m−3, respectively. Noncrustal K was correlated with OC and EC, indicating that biomass burning was a major contributor to the regional carbonaceous aerosol.
Convective–stratiform rainfall separation by cloud content
Authors: Sui Chung‐Hsiung , Tsay Ching‐Tung , Li Xiaofan
Published: August 2007

A method is proposed to separate the convective component of the precipitation from the remainder based on threshold values of vertically integrated content of ice clouds (ice water path, IWP), water clouds (liquid water path, LWP), and their ratio (cloud ratio). These cloud variables can be retrieved from satellite measurements and are physically linked to the cloud microphysics as demonstrated by an analysis of simulated cloud microphysics budgets in a two‐dimensional cloud‐resolving model subject to the imposed forcing from the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE). Our analysis suggests that rainfall can be designated convective when the corresponding value of cloud ratio < 0.2 or the value of IWP > 2.55 mm. The remaining grids are classified as mixed and stratiform when the corresponding range of cloud ratio is 0.2–1.0 and greater than 1, respectively. The method is evaluated by the vertical velocity (w) data. The frequency distribution of w shows that w in the convective region has a wide distribution of w, with maximum values exceeding 15 m s−1. In the designated stratiform region, the distribution is narrow, with absolute values of w confined within 5 m s−1. The statistics of w and the budgets of cloud microphysics are consistent with corresponding physical characteristics of the convective and stratiform regions of precipitation. The consideration of features like fractional cloud covers, rainrates, w profiles, and the corresponding wave response leads us to regard the mixed and stratiform regions as the non‐convective region.
Nocturnal temperature structure in the mesopause region over the Arecibo Observatory (18.35°N, 66.75°W): Seasonal variations
Authors: Friedman Jonathan S. , Chu Xinzhao
Published: August 2007

We present the mean seasonal climatology of the nocturnal temperature structure in the mesopause region (80–105 km) above the Arecibo Observatory, Puerto Rico (18.35°N, 66.75°W) from 106 nights of potassium Doppler lidar observations between December 2003 and September 2006. This first complete range‐resolved mesopause climatology for a tropical latitude exhibits several unique features. Compared to higher latitude sites, mesospheric temperature inversion layers in the nocturnal means are much weaker at Arecibo. Seasonally large inversions occur in summer but are almost non‐existent during the rest of the year. The Arecibo climatology shows a three‐level mesopause: a high altitude in summer (∼100 km), a medium altitude in late autumn and winter (∼96 km), and a low altitude in early spring (∼91 km). The mesopause is cold in the solstices (∼171 K in summer, ∼176 K in winter) and warm around equinoxes, particularly late autumn when it is near 195 K, while the spring mesopause temperature is close to 185 K. The lower thermosphere around 100 km at Arecibo shows a decreasing temperature from spring to summer when it reaches its coldest temperature, which is contrary to the increasing temperature observed at all midlatitude locations. Semiannual variations in the seasonal temperature have amplitudes as large as the annual variations through most of the MLT altitude range at Arecibo. These observed seasonal variations appear to be associated with the semi‐annual oscillation, a predominantly tropical phenomenon. This report provides one of the very few observations of the semi‐annual oscillation in lower thermosphere temperature.
Impacts of global climate change and emissions on regional ozone and fine particulate matter concentrations over the United States
Authors: Tagaris Efthimios , Manomaiphiboon Kasemsan , Liao Kuo‐Jen , Leung L. Ruby , Woo Jung‐Hun , He Shan , Amar Praveen , Russell Armistead G.
Published: August 2007

Simulated future summers (i.e., 2049–2051) and annual (i.e., 2050) average regional O3 and PM2.5 concentrations over the United States are compared with historic (i.e., 2000–2002 summers and all of 2001) levels to investigate the potential impacts of global climate change and emissions on regional air quality. Meteorological inputs to the CMAQ chemical transport model are developed by downscaling the GISS Global Climate Model simulations using an MM5‐based regional climate model. Future‐year emissions for North America are developed by growing the U.S. EPA CAIR inventory, Mexican and Canadian emissions and by using the IMAGE model with the IPCC A1B emissions scenario that is also used in projecting future climate. Reductions of more than 50% in NOX and SO2 emissions are forecast. Impacts of global climate change alone on regional air quality are small compared to impacts from emission control‐related reductions, although increases in pollutant concentrations due to stagnation and other factors are found. The combined effect of climate change and emission reductions lead to a 20% decrease (regionally varying from −11% to −28%) in the mean summer maximum daily 8‐hour ozone levels (M8hO3) over the United States. Mean annual PM2.5 concentrations are estimated to be 23% lower (varies from −9% to −32%). Major reductions in sulfate, nitrate and ammonium PM2.5 components combined with the limited reduction in organic carbon suggests that organic carbon will be the dominant component of PM2.5 mass in the future. Regionally, the eastern United States benefits more than the rest of the regions from reductions in both M8hO3 and PM2.5, because of both spatial variations in the meteorological and emissions changes. Reduction in the higher M8hO3 concentrations is also estimated for all subregions and fewer days with M8hO3 above the air quality standards in urban sites with Atlanta in the southeast benefiting most.