bluuebunny/crossref_metadata_2025 huggingface dataset:
STATE-SPECIFIC DISSOCIATION RATES FOR H2(v, j) + H2(v′, j′)
Authors: Mandy M. E.
Published: August 2016

State-specific rate coefficients for the dissociation of H2 as the result of collisions with H2 were calculated for all combinations of (v, j) with an internal energy below 1 eV. Full-dimensional quasiclassical trajectories were calculated using the BMKP2 interaction potential with a minimum of 80,000 trajectories at each translational energy. Additional large batches of trajectories were carried out to calculate the cross sections near the threshold to dissociation to attain the desired precision of the rate coefficients. A piecewise linear excitation function was used to calculate the rate coefficient between 100 and 100,000 K. The resulting state-specific rate coefficients, γ, were parametrized as a function of temperature over the range 600–10,000 K using:

where

K and

. The values of the resulting rate coefficients were sensitive to the internal energy of both molecules, with initial vibrational energy having a slightly greater effect than rotational energy. This effect diminished as temperature increased.
IMPLICATIONS OF THE TENTATIVE ASSOCIATION BETWEEN GW150914 AND A FERMI-GBM TRANSIENT
Authors: Li Xiang , Zhang Fu-Wen , Yuan Qiang , Jin Zhi-Ping , Fan Yi-Zhong , Liu Si-Ming , Wei Da-Ming
Published: August 2016

The merger-driven gamma-ray bursts (GRBs) and their associated gravitational-wave (GW) radiation, if both are successfully detected, have some far-reaching implications, including, for instance: (i) the statistical comparison of the physical properties of the short/long-short GRBs with and without GW detection can test the general origin model; (ii) revealing the physical processes taking place at the central engine; (iii) measuring the velocity of the gravitational wave directly/accurately. In this work, we discuss these implications in the case of a possible association of GW150914/Gamma-ray Burst Monitor (GBM) transient 150914. We compared GBM transient 150914 with other SGRBs and found that such an event may be a distinct outlier in some statistical diagrams, possibly due to its specific binary black hole merger origin. However, the presence of a “new” group of SGRBs with “unusual” physical parameters is also possible. If the outflow of GBM transient 150914 was launched by the accretion onto the nascent black hole, the magnetic activity rather than the neutrino process is likely responsible for the energy extraction, and the accretion disk mass is estimated to be ∼10−5
M
⊙. The GW150914/GBM transient 150914 association, if confirmed, would provide the first opportunity to directly measure the GW velocity, and its departure from the speed of the light should be within a factor of ∼10−17.
How climate change and regulations can affect the economics of mycotoxins
Authors: Wu F. , Mitchell N.J.
Published: August 2016

In the decades to come, the one factor that will likely have the greatest effect on the economics of the mycotoxin problem is climate change. This article reviews the current state of known science on how the global climate has been changing in recent decades, as well as likely climate change trends in the near future. The article focuses in depth on how climatic variables affect fungal infection and production of specific mycotoxins in food crops, and how near-future climatic changes will shape the prevalence of these mycotoxins in crops in different parts of the world. Because of regulatory limits set on maximum allowable levels of mycotoxins in food and feed, growers will experience economic losses if climatic factors cause certain mycotoxins to become more prevalent. A case study is presented of how maize growers in the United States will experience increased economic losses due to slightly higher aflatoxin levels in maize, even if those levels may still be below regulatory limits. We discuss the overall expected economic impacts of climate change-induced mycotoxin contamination worldwide – not just market-related losses, but also losses to human and animal health and risks to food security. Aflatoxin is the mycotoxin that is most likely to increase under near-future climate scenarios; and thus is likely to pose the greatest amount of economic risk of all the mycotoxins.
Numerical and Experimental Investigation of an Underplatform Damper Test Rig
Authors: Pesaresi L. , Salles L. , Elliott R. , Jones A. , Green J.S. , Schwingshackl C.W.
Published: August 2016

During operation mechanical structures can experience large vibration amplitudes. One of the challenges encountered in gas-turbine blade design is avoiding high-cycle fatigue failure usually caused by large resonance stresses driven by aeroelastic excitation. A common approach to control the amplitude levels relies on increasing friction damping by incorporating underplatform dampers (UPD). An accurate prediction of the dynamics of a blade-damper system is quite challenging, due to the highly nonlinear nature of the friction interfaces and detailed validation is required to ensure that a good modelling approach is selected. To support the validation process, a newly developed experimental damper rig will be presented, based on a set of newly introduced non-dimensional parameters that ensure a similar dynamic behaviour of the test rig to a real turbine blade-damper system. An ini-
tial experimental investigation highlighted the sensitivity of the measured response with regards to settling and running in of the damper, and further measurements identified a strong dependence of the nonlinear behaviour to localised damper motion. Numerical simulations of the damper rig with a simple macroslip damper model were performed during the preliminary design, and a comparison to the measured data highlighted the ability of the basic implicit model to capture the resonance frequencies of the system accuratelyю
Influence of Modal Coupling on the Nonlinear Vibration of Simply Supported Cylindrical Panels
Authors: da Silva Frederico Martins Alves , Sattler Henrique Araújo Rodrigues , Gonçalves Paulo Batista , del Prado Zenón José Guzmán Nunñez
Published: August 2016

The aim of this paper is to analyse the influence of the nonlinear modal coupling on the nonlinear vibrations of a simply supported cylindrical panel excited by a time dependent transversal load. The cylindrical panel is modeled by the Donnell nonlinear shallow shell theory and the lateral displacement field is based on a perturbation procedure. The axial and circumferential displacement are described in terms of the obtained lateral displacement, generating a precise low-dimensional model that satisfies all transversal boundary conditions. The discretized equations of motion in time domain are determined by applying the standard Galerkin method. Various numerical techniques are employed to obtain the cylindrical panel resonance curves, bifurcation scenario and basins of attraction. The results show the influence of geometry and the nonlinear modal coupling on the nonlinear response of the cylindrical panel.
Multi-Featured Content-Based Image Retrieval Using Color and Texture Features
Authors: Ayan Mehmet , Erdem O. Ayhan , Bilge Hasan Şakir
Published: August 2016

Content-based image retrieval (CBIR) system becomes a hot topic in recent years. CBIR system is the retrieval of images based on visual features. CBIR system based on a single feature has a low performance. Therefore, in this paper a new content based image retrieval method using color and texture features is proposed to improve performance. In this method color histogram and color moment are used for color feature extraction and grey level co-occurrence matrix (GLCM) is used for texture feature extraction. Then all extracted features are integrated for image retrieval. Finally, color histogram, color moment, GLCM and proposed methods are tested respectively. As a result, it is observed that proposed method which integrates color and texture features gave better results than the other methods used independently. To demonstrate the proposed system is successful, it was compared with existing CBIR systems. The proposed method showed superior performance than other comparative systems.
Design and Implementation of a Solar Controller and PC Data Acquisition System for PV Energy Applications
Authors: Dursun Mahir , Özden Semih
Published: August 2016

In this study, a mainboard was designed for solar energy control with PC data acquisition system. The released system included forty-eight pieces of PV panels, 1.92 kW BLDC and eight pieces of 65 Ah batteries. The buck type DC-DC converter was controlled to charge battery depending on its voltage and current scheme. The BLDC motor was coupled to a pump and a MOSFET was used as motor run/stop switch for automatic working. This system was applied to irrigation in Turkey that it is consist of 1000 pieces of dwarf cherry tree. The controller had communication with PC and DAQ card. All analog values of system (currents, voltages, temperatures, etc.) send to PC with RS-232 and DAQ with reading analog values.
Reducing Voltage Fluctuations in Wind Turbines by SVC Method
Authors: Jahi Amir , Tezcan S.S.
Published: August 2016

Today because of increasing wind generation in the power systems, voltage variations are critical in power quality of grid combination of wind energy. This paper presents a Static Var Compensator (SVC) as an efficient choice for the reactive power regulation of wind turbines to decrease voltage fluctuations, and the proposed modulation is performed for the cases with and without SVC. The simulation showed the effective influences of the SVC on the voltage characteristic with the unexpected changes in the voltage magnitude.
Characteristic Evaluation of Multiple Layers Microwave Absorber Coated with Biomass Composite
Authors: Abdullah Hasnain , Zanal Asmalia , Ahya Ilmudin Mohamad Hakim , Taib Mohd Nasir , Md Sharif Juliana , Nizam Malek Mohamad Khairul , Baharudin Rohaiza , Mohamed Noordin Ida Rahayu , Razali Ahmad Rashidy
Published: August 2016

Radiation Absorbing Material (RAM) is used to absorb radiations of electromagnetic wave surrounding us. Thus, the multiple layers’ microwave absorber using biomass composite materials could be one of the solutions to address the problem. In order to effectively absorb the radiation of electromagnetic wave, the multiple layers’ absorber is characterized to optimize the performance of the absorber. The characterization is made by varying biomass composite material contents, thickness and other possible considerations. CST Microwave Studio software is first used to design and simulate the multiple layers’ absorber to estimate its performance. Development of multiple layers’ prototype is carried out to test its performance at free space environment. Free space dielectric measurement method is used to determine the value of multiple layers’ absorber dielectric. The dielectric value is then used in CST software in order to make the simulation more precise. Free space arch which is connected to Agilent Analyzer is used to measure absorption of multiple layers’ microwave absorber.
A New Hybrid Frequency Selective Surface Design in the 2.4GHz and 5.8GHz ISM Bands
Authors: Döken Bora , Kartal Mesut
Published: August 2016

With the advancement in telecommunication in indoor environment, the use of wireless technology for information systems has drastically increased. The intensive use of indoor wireless devices in 2.4GHz and 5.8GHz ISM bands causes mutual interference in neighboring networks which degrades the system performance. Secure personal communication within such wireless networks is also another important problem. A band-stop frequency selective surface (operating in the WLAN frequency band) which is attached to the walls of buildings can provide a solution for these interference and security problems. In this work, a new band-stop hybrid frequency selective surface element consisting of two circular looped type geometries is introduced which is capable of attenuating the incoming 2.4GHz and 5.8GHz ISM signals minimum 13dB for all polarizations and incident angles varies from 00 to 450. Besides, a periodic cell size (p=26,5mmm) which is almost one fifth of the first resonance wavelength is obtained.
Consulenza in bioetica clinica. Una proposta
Authors: Cattorini Paolo M.
Published: August 2016

Diversi fattori etici alimentano l’esigenza di giustificare razionalmente le decisioni sanitarie, in particolare al letto del malato: il pluralismo culturale, il tramonto del paternalismo, l’interdisciplinarità dei problemi, l’alto livello di specializzazione tecnologica. Un consulente, strutturato in servizi di bioetica clinica, può aiutare i diversi attori morali ad approfondire il loro punto di vista, discuterlo coerentemente, raggiungere soluzioni di compromesso. Per evitare atteggiamenti di indottrinamento, faziosità, deresponsabilizzazione, questa nuova figura professionale dovrebbe possedere alcune qualità essenziali, documentate e addestrate in supervisione. ---------- Health care decisions are to be taken in a rationally justified way, into a pluralistic ethical arena and through an interdisciplinary dialogue among naturalistic and humanistic disciplines. A professional figure of clinical ethicist, working in specific departments, is needed to help people to deepen their personal moral evaluations, and to foster and facilitate coherent and shared decisions, both at individual, staff and institution level. Particularly at the bedside, paternalistic and directive counselling might be avoided, if some core competencies and skills in applied ethics are trained.
Perché? Come? Chi? Tre domande (e alcune risposte) sulla consulenza etica in ambito sanitario
Authors: Semplici Stefano
Published: August 2016

Le questioni sempre più complesse che emergono nella pratica clinica, in conseguenza del progresso scientifico e tecnologico e del crescente pluralismo di valori e stili di vita, hanno rafforzato l’esigenza di una specifica consulenza, con lo scopo di tutelare l’autonomia dei pazienti e offrire loro maggiori e più informate opportunità di scelta. Ci sono tuttavia molte questioni che meritano un approfondimento: il modello della consulenza (interi comitati, piccoli gruppi, singoli consulenti); il ruolo del punto di vista morale dei consulenti; le loro competenze; il rischio che la consulenza possa diventare un privilegio per pochi. ---------- The more and more complex issues that are emerging in clinical practice, as a consequence of scientific and technological progress as well as of growing pluralism of values and lifestyles, have strengthened the need for a specific consultation, aiming at protecting the patients’ autonomy and providing them with greater and more informed opportunities of choice. However, many questions are worth a deeper insight: the models of consultation (full committees, small teams, individual consultants); the role of the consultants’ moral point of view; their expertise; the risk for consultation to become a privilege for few.
Comparison of Immunocytochemistry and Immunohistochemistry on Breast Carcinoma: A Boon or a Bane?
Authors: Geethamala Kempula , Murthy Venkataramappa Srinivasa , Vani Bangalore Ramalingiah , Rao Madireddi Sudha , Thejaswini Malugnalli Uddappa , Padmaja Krishnarajapet Padmanabha
Published: August 2016

Introduction: Breast carcinoma is the most common cancer among women in the urban Indian population. Conventionally, immunohistochemistry (IHC) is done to determine the hormone receptor status of the tumor. Immunocytochemistry (ICC) on fine‑needle aspiration cytology (FNAC) was carried out to determine the same hormone receptor status of the tumor.

Objective: The study was undertaken to evaluate the diagnostic reliability of performing estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (Her2/neu) receptor status on FNAC by ICC and to compare the results with IHC.

Materials and Methods: A 2 years 6 months prospective study conducted in the Department of Pathology, ESIC Medical College and PGIMSR and ESIC Model Hospital, Rajajinagar, Bengaluru, wherein 100 breast carcinoma patients’ samples both cytology and histology were collected. IHC and ICC were done by peroxidase antiperoxidase technique. Validations of the receptor status were analyzed using sensitivity, specificity, positive and negative predictive values (PPV and NPV), and kappa statistics for agreements between ICC and IHC.

Results: ICC was positive for ER, PR, and Her2/neu in 53, 50, and 22 cases, respectively. For ER, a cytohistologic correlation of 98%, with a sensitivity of 96.3%, specificity of 100%, and PPV and NPV being 100% and 95.7%. For PR, concordance of 97%, with a sensitivity of 94.3%, specificity of 100%, and PPV and NPV being 100% and 94%. Her2/neu had an agreement of 89%, with a sensitivity of 72%, specificity of 95.5%, and PPV and NPV being 85.7% and 90.1%.

Conclusion: ICC has been a boon and can be a paramount diagnostic adjunct to the routine investigations.
Internal Carotid Artery Fibromuscular Dysplasia in a Child: Incidental Postmortem Finding after Head Injury
Authors: Subramanian Arulselvi , Aggarwal Garima , Agarwal Deepak , Lalwani Sanjeev
Published: August 2016

Fibromuscular dysplasia (FMD) is a rare, segmental, nonatheromatous, and noninflammatory arterial disease of unknown etiology. It predominantly involves renal artery (60–75%) followed by extracranial part of the internal carotid artery and vertebral arteries (25–30%). The disease typically affects middle-aged women and involves intermediate-sized arteries throughout the body. There are rare case reports of extracranial FMD compounding a trauma case. A patient was brought to trauma center emergency with a history of fall from height. There were one previous episode of seizure and two episodes of vomiting. His Glasgow Coma Scale on admission was E1V1M4. Noncontrast computed tomography of the head showed fracture on the right zygomatic, temporal, and parietal bone, with underlying thin subdural hemorrhage. The patient underwent left frontotemporoparietal decompressive craniectomy and lax duraplasty with bone flap in bone bank. On the 1st postoperative day, he succumbed to his injuries despite timely surgery and necessary interventions. It was only postmortem when FMD was diagnosed in carotid artery by histopathological examination. On microscopy, intimal changes were seen in the form of expansion of subendothelial loose matrix with mesenchymal cells, thickening and hyalinization of the internal elastic lamina, areas of duplication and disruption of internal elastic lamina. Medial wall changes included thickening of the wall, focal loss of the smooth muscle, and replacement with fibrosis (dysplastic change). This case emphasizes the importance of considering this disease in the differential diagnosis of children and young adults with stroke (which subsequently lead to his fall).
Performance of Xpert MTB/RIF on Ascitic Fluid Samples for Detection of Abdominal Tuberculosis
Authors: Rufai Syed Beenish , Singh Sarman , Singh Amit , Kumar Parveen , Singh Jitendra , Vishal Anand
Published: August 2016

Background: Diagnosis of abdominal tuberculosis (TB) from ascitic fluid samples using routinely available diagnostic methods is challenging due to its paucibacillary nature. Although performance of Xpert MTB/RIF assay has been evaluated extensively on pulmonary samples, its performance on extrapulmonary samples is still under evaluation.

Objectives: The objective of this study was to find out the performance of Xpert MTB/RIF on ascitic fluid samples obtained from suspected cases of abdominal TB. Performance was compared with Mycobacterium growth indicator tube-960 (MGIT-960) culture and in-house multiplex polymerase chain reaction (PCR). The latter detects and differentiates Mycobacterium tuberculosis and nontuberculous mycobacteria simultaneously.

Materials and Methods: Sixty-seven patients suspected of probable/possible abdominal TB were included in this observational, prospective study. All samples were tested by Ziehl–Neelsen staining, MGIT-960 culture, in-house multiplex PCR, and Xpert MTB/RIF assay.

Results: All 67 samples were smear negative. Seventeen (25.4%) were MGIT-960 culture positive while 12 (17.9%) were detected positive by the Xpert MTB/RIF assay and 9 (13.4%) by in-house multiplex PCR. Sensitivity and specificity of the Xpert MTB/RIF assay compared with the MGIT-960 culture were 70.6% (95%, confidence interval [CI]: 44.1–89.7) and 100% (95%, CI: 92.8–100) and that of in-house multiplex PCR were 52.9% (95%, CI: 30.9–73.8) and 100% (95%, CI: 92.8–100), respectively.

Conclusions: Diagnostic yield of Xpert MTB/RIF assay on ascitic fluid samples was lower than MGIT-960 culture. We thus emphasize on the need for urgent discovery of new biomarkers for paucibacillary TB.
KINETIC STUDIES ON ALKALINE PHOSPHATASE FROM ECHINOPLUTEI1
Authors: Hsiao Sidney C.
Published: August 2016

Using mass culture of the sea urchin Tripneustes gratilla (L.) eggs, a method was worked out for extracting fairly large quantities of the phosphomonoesterase alkaline phosphatase. The extracted enzyme showed a single ultraviolet absorbance band after elution from a Dowex 2 column, and the material that absorbed most strongly at this wave length contained alkaline phosphatase. It showed two characteristic bands in starch‐gel electrophoresis. When 6.25 mM p‐nitrophenyl phosphate was hydrolyzed in glycine buffer at 38C, the optimum pH was 10.5. The hydrolysis conformed to a first order reaction, and the reaction constant was 0.00864 min‐1. The optimum temperature for enzymatic action was 25–30C, coinciding with the range of fluctuation of the animal's ambient temperature. The temperature–activity curve showed a close conformity to the Arrhenius equation, and the activation energy was 11,250 cal/mole. The value of Km (Michaelis constant) obtained at pH 10.5 (at 25C) is 2.197 × 10‐6 M of p‐NPP/liter.
A MATHEMATICAL MODEL OF REGIONAL VARIATIONS IN PLANKTON
Authors: Riley Gordon A.
Published: August 2016

The relationships of phytoplankton, zooplankton, and a limiting nutrient (phosphate) arc examined in a simple two‐layered model in which the upper layer corresponds with the maximum limits of the euphotic zone and is regulated in its depth by the effect of the chlorophyll content of the phytoplankton upon light absorption. The model is applied to quasi‐steady state conditions in summer, when radiation values are similar over wide geographical areas, so that radiation is treated as a constant. Basic environmental variables include a) phosphate concentration in the deepwater mass underlying the euphotic zone, b) the rate of mixing between the two layers, and c) temperature, which is postulated to be important in affecting the sinking rate of phytoplankton. For any given array of environmental factors, steady state concentrations of phytoplankton, zooplankton, and phosphate in the upper layer can be calculated. In two areas in the Atlantic Ocean, one in boreal waters of the North Sea and one in the subtropics off Bermuda, environmental factors and populations have been determined with sufficient precision for a good test of the model, and the results are realistic. Chlorophyll data are then examined on a broader regional scale, and again there are indications that the model provides a reasonable fit for most of the observed variations.
THE VERTICAL DISTRIBUTION OF THE INVERTEBRATE FAUNA IN THE BED OF A STREAM1
Authors: Coleman Mary J. , Hynes H. B. N.
Published: August 2016

A type of sampler is described that permits the collection of benthic fauna to a depth of 30 cm in the beds of streams. It depends on the colonization of natural substratum placed into the streambed, and invasion can occur both horizontally and vertically downward. When fully colonized, these samplers collect many times the number of animals taken by vigorous stirring of the substratum upstream of a net.

Sets of samplers in which only one of four possible horizontal layers about 7.5 cm deep was available for colonization were emplanted in an Ontario stream and lifted from 1 to 28 days later.

The total numbers of many types of animals increased steadily with time in all 4 layers; more than 28 days are probably needed for full colonization. When all the catches are considered together only about 20% of the total was in the top layer, about 26% was in the bottom layer, and the rest was about evenly distributed in the two middle layers. This type of distribution was found for all the groups of animals present. Only Simulium appeared to be normally confined to the surface of the substratum.

It is suggested that significant numbers of animals occur deep within the substrata of stony streams, and that even samples collected down to 30 cm do not adequately represent the fauna.
THE DIVERSITY OF PIGMENTS IN LAKE SEDIMENTS AND ITS ECOLOGICAL SIGNIFICANCE1
Authors: Sanger Jon E. , Gorham Eville
Published: August 2016

Thin‐layer chromatography shows a large number of pigments (chlorophyll derivatives and carotenoids) in profundal lake sediments, diversity being somewhat greater in eutrophic than in oligotrophic lakes. Sedimentary pigments are much more numerous (24–47) than those of upland vegetation (7–8), aquatic macrophytes (12–15), and planktonic algae (10–21). Algal decomposition, which is accompanied by a marked increase in number of pigments, seems the most likely cause for the extreme diversity of sedimentary pigments.
COMPLEMENTARY FEEDING NICHES SUSTAINED BY SIZE‐SELECTIVE PREDATION1
Authors: Dodson Stanley I.
Published: August 2016

A study of the planktonic communities of 24 similar ponds in the mountains of Colorado supports the hypothesis that one predator population can sustain another as a result of size‐selective predation on the prey of both predators. A highly selective predator excludes its preferred (large) food items and thus favors the presence of suboptimal (smaller‐sized) prey populations which are the preferred food of the second, dependent, predator. The suboptimal prey species are found only with size‐selective predators, and it is probable that these are the only suitable prey species for the dependent predator. This interaction can occur in simple communities but also appears to be common in more diverse, complex communities. To support the discussion of this interaction, the electivity coefficients and predation pressures of three freshwater planktivores were estimated.
Nitrogen fixation in freshwater, estuarine, and marine ecosystems. 2. Biogeochemical controls1
Authors: Howarth Robert W. , Marino Roxanne , Cole Jonathan J.
Published: August 2016

Planktonic nitrogen fixation in lakes is strongly related to lake trophic status, with moderate and high rates usually occurring only in eutrophic lakes. Among eutrophic lakes, nitrogen fixation is related to the ratio of nitrogen loading to phosphorus loading to the lake; significant nitrogen fixation by planktonic organisms generally occurs only when the N: P ratio of the nutrient loading is near or below the Redfield ratio of 16: 1. In contrast, nitrogen fixation by planktonic organisms is generally low in estuaries even when the N: P ratio of nutrients inputs is low.

The tendency toward less nitrogen fixation by plankton in estuaries and coastal marine ecosystems than in lakes subject to similar loadings of nitrogen and phosphorus may be due to a lower availability in oxic seawater of one or more trace elements required for nitrogen fixation, such as molybdenum and iron. Iron concentrations are generally lower in estuarine waters and seawater than in most lakes. And although molybdenum concentrations in seawater are actually higher than in lakes, molybdenum availability is probably lower, since sulfate inhibits molybdate assimilation by microbes. Molybdate is the primary form of molybdenum in oxic seawater, and the ratio of sulfate: molybdate is greater than in lakes. However, even in lakes sulfate is several orders of magnitude more abundant than molybdenum, and the ratio of dissolved sulfate to dissolved molybdenum typically is much greater than the ratio of sulfur to molybdenum apparently required by nitrogen‐fixing cyanobacteria. Consequently, assimilation of molybdate by cyanobacteria is probably an energetically expensive process in all natural waters, but more so in seawater than in freshwaters. High concentrations of dissolved organic matter are known to favor blooms of cyanobacteria, perhaps by increasing iron and/or molybdenum availability through chelation.

The primary controls on nitrogen fixation in sediments, wetlands, macrophyte beds, and cyanobacterial mats may be different from those for fixation by planktonic organisms. Both molybdenum and iron are probably more available in these systems than in oxic waters, since reducing conditions and high DOC concentrations will increase iron solubility and favor the stability of reduced forms of molybdenum; sulfate should not inhibit the assimilation of these reduced molybdenum compounds. Consequently, nitrogenase synthesis (and, therefore, nitrogen fixation) in wetlands and in sediments may be less energetically expensive than in oxic water columns. A major control on nitrogen fixation in sediments may be repression of nitrogenase synthesis by high concentrations of ammonium, a factor less important to planktonic fixation because of the much lower concentrations of ammonium generally found in water columns than in sediments.
A comparison of the ecology of planktonic bacteria in fresh and salt water
Authors: Hobbie John E.
Published: August 2016

The planktonic bacteria inhabiting fresh and salt waters are not physiologically identical; most marine bacteria, for example, require sodium and some marine forms can thrive at 1,000 atm of pressure in the deep sea. Despite this difference, the conclusion of this review is that the ecology of planktonic bacteria is virtually identical in fresh and salt waters.

The differences are small and mostly a matter of relative proportion of various processes. That is, similar bacterial processes occur in fresh and salt waters but in each environment, one process may be more important than another. For example, bacteria in freshwaters are exposed to high amounts of refractory dissolved organic carbon from soil and stream runoff, while many marine bacteria are exposed to relatively more of the labile organic matter from decaying algae. Also, under anaerobic conditions the sulfur cycle will be dominant in the sea while the carbon‐methane cycle will be more important in freshwaters. In spite of the presence of relatively high amounts of methane in the sea, there is thus far little evidence that a significant amount of methane is being oxidized.

Not enough is yet known to determine if there are differences in the grazing of bacteria in the two systems. Small, flagellated protozoans are very important grazers in freshwater and marine systems but there is some evidence from salt waters that ciliates are also important grazers. Marine ecosystems also contain large animals that can filter out bacteria. Sponges are the dominant suspension feeders on coral reefs, mussels and oysters are dominant in estuarine and marsh systems, and a large appendicularian may filter significant amounts of bacteria through a mucous net.

Ecological understanding of the aquatic bacteria has advanced rapidly in the past two decades. One reason is the basic similarity between microbial ecology in fresh and salt waters and the consequent interchangeability of techniques.
Phototrophic picoplankton: An overview from marine and freshwater ecosystems
Authors: Stockner John G.
Published: August 2016

Algal picoplankton are a ubiquitous component of the microbial plankton communities of both marine and freshwater ecosystems. They contribute significantly to the total biomass of phytoplankton communities, and in oligotrophic oceans and lakes can be responsible for up to 80–90% of the total daily or annual carbon production. As part of the “microbial loop,” they are thought to be grazed by flagellates, ciliates, rotifers, copepods, and other metazoans, and contribute to the flow of energy to higher trophic levels. This presentation highlights their discovery, distribution, physiology, production, and contribution to pelagic food webs in marine and freshwater systems.
Comparative ecology of submersed grass beds in freshwater, estuarine, and marine environments1
Authors: Stevenson J. Court
Published: August 2016

Worldwide, there are 500–700 species of submersed angiosperms adapted to freshwater and estuarine environments compared with 50 species adapted to marine waters. In their evolution from freshwater ancestors, seagrasses have undergone extensive anatomical changes (e.g. reduction in floral and leaf structures, reduction of xylem tissue with a lacunal gas transport system), as well as physiological adaptations (bicarbonate utilization in photosynthesis). Seagrasses appear to have more annual production than do their freshwater counterparts because they develop greater standing crops and have the capacity to store photosynthetic products in extensive rhizome systems in the sediments. For example, maximum productivity of >10 g C m−2 d−1 has been reported for tropical seagrass species (Cymodocea nodosa and Thalassia testudinum), but the maximum productivity of temperate freshwater species such as Myriophyllum or tropical freshwater species such as Hydrilla is usually <5 g C m−2 d−1. In addition, the marine environment provides ample supplies of inorganic carbon (C) and increased mixing energies, making CO2 limitation less likely. One calculation suggests that marine macrophytes impact the global C budget by sequestering as much as 109 t of C per year.

Secondary productivities of seagrass communities can also be high. For example, stable isotopic ratios suggest that macrophytic C is important in sustaining several species of commercial fish species in Australia, accounting for >50% of their diets. Also, sea urchins (Diadema antilarum) consume plant material, creating bare halos around tropical patch reefs in the Caribbean Sea. It is difficult to generalize regarding brackish submersed aquatics in estuaries because their coverage is variable due to light limitation and algal overgrowth from eutrophication. Freshwater macrophytes seem rarely grazed by fish (except via exotic introductions of Tilapia or carp), but waterfowl use is often significant at the end of the growing season. Thus, trophic relations in freshwater macrophyte beds may be qualitatively different and much more pulsed than in seagrass systems, with more re‐selection in lakes and more K‐selection in marine environments.
Alkalinity generation in a soft‐water lake: Watershed and in‐lake processes
Authors: Psenner Roland
Published: August 2016

Alkalinity mass balance studies of the oligo‐mesotrophic soft‐water Piburger See (913 m ASL) over a period of 11 yr showed annual rates of in‐lake alkalinity generation from 24 to 144 µeq liter‒1, or 0.33 to 1.97 eq m‒2. From nitrogen, sulfur, and iron budgets, alkalinity generation rates of 21–38 µeq liter‒1 yr‒1 (0.37–0.52 eq m‒2 yr‒1) were inferred. Reduction of the artificial deep‐water discharge by ∼40% led to doubling of the rates of in‐lake alkalinity production. The processes which generated alkalinity in the lake were release of calcium (37%) and magnesium (18%) from sediment or suspended matter and the reduction of sulfate (20%), nitrate (16%), and iron (9%). Budget studies based on alkalinity measurements showed 12–21% lower values than the sum of alkalinity calculated from dissimilation and release. The difference can be explained by uncertainties in the measurement of elemental cycles in the water column (nitrogen fixation vs. denitrification) and sediments (Fe: S stoichiometry of iron sulfide precipitation) and budget errors. The areal rate of net alkalinity generation in the watershed of Piburger See accounted for 5–27% of that produced in the lake. As a whole, the catchment produced 100–500% of the in‐lake alkalinity.
Nitrogen nutrition and physiological state of natural populations of phytoplankton in surface waters of the western Pacific Ocean
Authors: Kanda Jota , Saino Toshiro , Hattori Akihiko
Published: August 2016

Nitrogen nutrition of natural populations of phytoplankton in surface waters of the western North Pacific was investigated with an intracellular 15NH4+‐partitioning technique. At three oligotrophic stations, rate of 15N incorporation into macromolecular components was almost identical with uptake rate, suggesting that phytoplankton are not nitrogen deficient. 15N accumulation in extractable components was inferred from data obtained at two other oligotrophic stations. At these stations, phytoplankton growth is apparently limited by nitrogen supply. At three mesotrophic stations, a similar but less pronounced 15N accumulation in extractable components occurred, which may be attributed to enhanced ammonium uptake caused by the exposure of phytoplankton grown on nitrate to high concentrations of ammonium.
Sex size ratios and their influence on mating success in a calanoid copepod
Authors: Grad Gabriella , Maly Edward J.
Published: August 2016

Mating experiments with 182 individual pairs of Diaptomus birgei Marsh were videotaped in the laboratory. The following were measured and scored: attempted capture of the female by the male, time to successful capture and mounting, duration of copulation, spermatophore placement, time to clutch extrusion, metasomal lengths of all individuals, and sex size ratios (female: male lengths) of all pairs. The percentages of successful copulation and clutch formation were highest between sex size ratios of 1.15 and 1.23. The average sex size ratio of 1.20 is apparently selected for, since it was relatively constant over time in the observed natural populations.
The impact of population abundance on the deposit‐feeding rate of a cosmopolitan polychaete worm
Authors: Wheatcroft Robert A. , Starczak Victoria R. , Butman Cheryl Ann
Published: August 2016

The impact of population abundance on the deposit‐feeding rate of Mediomastus ambiseta (Capitellidae: Polychaeta) was studied in still‐water laboratory experiments. Mean individual pellet production rate (mg worm−1 d−1) decreased monotonically with increasing worm abundance in the range of 6.5 X 103 to 1.3 X l05 worms m−2. Worms fed roughly an order of magnitude slower in the high‐density treatment than in the low‐density treatment. The vertical distribution of pellets (i.e., sites of egestion), however, was insensitive to changes in worm abundance. Despite the high population abundances, the weight‐% of pellets in the highest abundance treatments was <20%. Therefore, contrary to expectations, it was unlikely that feeding rate was limited by the availability of ingestable particles. Rather, some combination of resource depletion and possibly of enhanced physical or chemical interference caused the observed decline in feeding rate at higher population abundances. These results suggest that studies that seek to transfer laboratory‐based measures of deposit‐feeding rate to the field must be careful to match abundances in the two domains.
What controls the mixed‐layer depth in deep‐sea sediments? The importance of particulate organic carbon flux
Authors: Boudreau Bernard P.
Published: August 2016

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Contribution of river‐borne soil organic carbon to the Gulf of Lions (NW Mediterranean)
Authors: Kim J.-H , Zarzycka B. , Buscail R. , Peterse F. , Bonnin J. , Ludwig W. , Schouten S. , Sinninghe Damsté J. S.
Published: August 2016

We determined the spatial distribution patterns of the Branched and Isoprenoid Tetraether (BIT) index, a specific proxy of riverborne soil organic carbon (OC) input from land to the ocean, by analyzing soils from the Têt watershed (France) and surface sediments from the Gulf of Lions (NW Mediterranean) into which the Têet and Rhône Rivers flow. The BIT index pattern in the Têt watershed is heterogeneously distributed, varying between 0.2 and 1.0, with an average BIT value of 0.84 ± 0.14 (n = 58). Soil pH is the major factor controlling soil BIT values among the environmental factors considered on the basis of the statistical analysis of environmental parameters and glycerol dialkyl glycerol tetraether concentrations. In the Gulf of Lions, BIT values range from 0.01 to 0.85, with higher values along the coast compared with those offshore. The soil OC contributions to the total organic carbon (TOC), estimated on the basis of the BIT index, are > 10% along the coast, whereas those from the outer shelf and the continental slope are < 10%.
Methanogenic pathway, 13C isotope fractionation, and archaeal community composition in the sediment of two clear‐water lakes of Amazonia
Authors: Conrad Ralf , Klose Melanie , Claus Peter , Enrich-Prast Alex
Published: August 2016

We studied the methanogenic pathway and archaeal community composition in the sediment of two clearwater lakes, Lake Batata and Lake Mussura, in Amazonia. We measured CH4 production and δ13C of CO2, CH4, and acetate‐methyl in the presence and absence of CH3F, an inhibitor of acetotrophic methanogenesis. The fractionation factor of methanogenesis from CO2 was rather high in both lake sediments, which was consistent with the low concentrations of H2 and the small negative Gibbs free energy of hydrogenotrophic methanogenesis. The δ13C of acetate‐methyl was relatively low compared to that of organic matter and decreased further upon inhibition of acetate consumption by CH3F. Collectively, the data possibly suggest involvement of syntrophic acetate oxidation besides acetotrophic methanogenesis. The isotopic data were used to calculate the percent contribution of CO2 reduction to total methanogenesis, which was rather high (approximately 53–63%). Copy numbers of bacterial and archaeal 16S ribosomal ribonucleic acid (rRNA) genes were about 10‐fold higher in Lake Mussura than in Lake Batata, indicating that microbial numbers were not a limiting factor for production rates of CH4, which were similar in both lake sediments. The composition of the archaeal community was analyzed by cloning and sequencing of the genes coding for 16S rRNA and methyl coenzyme M reductase (mcrA), demonstrating the presence of acetotrophic Methanosaetaceae and different hydrogenotrophic methanogenic orders (Methanomicrobiales, Methanobacteriales, Methanocellales) in both lake sediments. Although methanogenic communities and pathways were principally comparable to those found in lake sediments of the midlatitudes, there were several particularities, e.g., the possible involvement of syntrophic acetate oxidation.
The response of giant kelp (Macrocystis pyrifera) in southern California to low‐frequency climate forcing
Authors: Parnell P. Ed , Miller Eric F. , Cody Cleridy E. Lennert , Dayton Paul K. , Carter Melissa L. , Stebbinsd Timothy D.
Published: August 2016

The nutrient climate on the inner shelf off southern California changed markedly across the 1976‐1977 North Pacific climate regime shift. With respect to giant kelp (Macrocystis pyrifera) canopies off southern California, the nitrate climate shifted from relatively replete conditions prior to the regime shift to depleted conditions afterward, and the dynamics of 14 giant kelp forests appeared to change as a result. The response of giant kelp to nutrient‐replete years before the regime shift was dampened compared to their response afterward. The sensitivity of these kelp‐forest canopies to nutrient limitation appears to have increased since the regime shift. This intensification of physical control after 1977 is evident in the strong correlation of seawater density δ and M. pyrifera density. The linear fit of the percent of time the 25.1 δ t isopycnal bathes the inner shelf, accounted for ~ 71% of the variability in kelp density off Point Loma, and the median depth of this isopycnal has deepened ~ 5 m since the regime shift. The wave climate also intensified beginning in the early 1970s. The dampened kelp response prior to the regime shift was likely due to greater biological control of kelp canopies via consumer and competitive processes (i.e., biological modulation) or decreased physical control at possibly many trophic levels. Our results suggest that the response of kelp forests to El Niño Southern Oscillation events is mediated by lower frequency climate modes that may modulate the regulatory importance of biological and physical processes on giant kelp.
The invasive ctenophore Mnemiopsis leidyi poses no direct threat to Baltic cod eggs and larva
Authors: Jaspers Cornelia , Titelman Josefin , Hansson Lars Johan , Haraldsson Matilda , Ditlefsen Christine Røllike
Published: August 2016

Since its invasion in to the Baltic Sea in 2006, the ctenophore Mnemiopsis leidyi has been suspected of serious predation on the early life stages of Baltic cod (Gadus morhua callarias L.) due to a temporal and spatial overlap in the most important cod spawning ground, the Bornholm Basin. We conducted laboratory incubation experiments and video observations to quantify feeding rates on Baltic cod eggs and larvae. Ingestion rates increased with cod larvae concentrations up to 8 prey L−1, beyond which ingestion remained constant. Neither Mnemiopsis size nor egg concentration (1–16 prey L−1) affected feeding rates on cod eggs. Observed feeding rates pooled from all experiments conducted at nonsaturating prey concentrations were low, with the highest volume‐specific clearance on < 4.5‐d‐old yolk‐sac larvae (0.05 ± 0.02 L (mL Mnemiopsis)−1 h−1), and lower rates on 4.5‐8‐d‐old larvae (0.02 ± 0.02 L (mL Mnemiopsis)−1 h−1) and eggs (0.02 ± 0.03 L (mL Mnemiopsis)−1 h−1). When offered Artemia salina and cod eggs simultaneously, Mnemiopsis passively selected against cod eggs. Video recordings showed that eggs did not trigger the capture response that Mnemiopsis shows toward motile prey, and ingested eggs were often ejected (88%, n = 8). Applying our clearance rates to in situ abundances of cod eggs, larvae, and Mnemiopsis for the peak of the spawning season, we demonstrate that the predation pressure of the invasive ctenophore is negligible. We conclude that Mnemiopsis constitutes no direct threat to the Baltic cod population.
Nitrogen transformations in a through‐flow wetland revealed using whole‐ecosystem pulsed 15N additions
Authors: O'Brien Jonathan M. , Hamilton Stephen K. , Kinsman-Costello Lauren E. , Lennon Jay T. , Ostrom Nathaniel E.
Published: August 2016

We used pulsed and continuous additions of 15N together with whole‐ecosystem metabolism measurements to elucidate the mechanisms of nitrogen (N) transformations in a small (1170 m2) through‐flow wetland situated along a stream. From measurements of the wetland inflow and outflow, we observed a consistent decrease in nitrate (by 10% of inflow concentrations), while ammonium increased by an order of magnitude. Outflow ammonium concentrations oscillated in a diel cycle, inverse to the concentration of dissolved oxygen (i.e., greater ammonium export at night). The pulsed 15N additions showed little uptake of nitrate over time in the wetland and rapid daytime uptake of ammonium from the water column (rate constant, kt = 0.11 h−1). A steady‐state 15N‐ammonium addition demonstrated a similar rate of ammonium uptake (kt = 0.067 h−1), no detectable nitrification, and highlighted the spatial pattern of ammonium and nitrate uptake within the wetland. Porewater concentration profiles suggest high rates of net ammonium diffusion from the sediments. Ecosystem metabolism measurements indicate that release was attenuated during the day by autotrophic uptake, resulting in lower ammonium export during the day. Denitrification rates were modeled from dissolved N2 : Ar ratios, but they were not sufficient to account for the observed loss in nitrate. Nitrate was removed near the pond inflow but not actively cycled throughout the pond, while the balance between sediment release and subsequent uptake of ammonium from the water‐column dominated N cycling in this wetland.