bluuebunny/crossref_metadata_2025 huggingface dataset:
Biopsy needle tips with markers—MR compatible needles for high‐precision needle tip positioning
Authors: Müller‐Bierl Bernd M. , Martirosian Petros , Graf Hansjörg , Boss Andreas , König Claudius , Pereira Philippe L. , Schick Fritz
Published: June 2008

Needle tip visualization is of high importance in magnetic resonance imaging (MRI) guided interventional procedures, for example for taking biopsies from suspicious lesions in the liver or kidney. The exact position of the needle tip is often obscured by image artifacts arising from the magnetic properties of the needle. The authors investigated two special biopsy needle tip designs using diamagnetic coatings. For common interventional MR sequences, the needle tip can be identified in the MR image by several equidistant dark spots arranged along a straight line. A dotted instead of a solid line allows for an improved control of the movement of the needle, not only if the needle is tilted toward the imaging plane, but also if the needle leaves an empty canal with signal extinction, which cannot be distinguished from the needle material itself. With the proposed design the position of the needle tip can be estimated with a precision of approximately 1 mm using conventional FLASH, FISP, and TSE sequences, as used for interventional MR. Furthermore, the size of the biopsy probe can be estimated from the artifact. In using needles with a properly designed tip coating, taking biopsies under MR control is beginning to be greatly simplified. The approach to design artifacts using diamagnetic material in combination with paramagnetic material paves the way toward new instruments and implants, suitably tailored to the needs of the interventional radiologist.
Radiochromic film dosimetry: Reflection vs transmission scanning
Authors: Kalef‐Ezra J. , Karava K.
Published: June 2008

The objective of this study was to compare the transmission and the reflection scanning reading modes of radiochromic MD‐55 films of a document scanner. The use of the red channel of the red‐green‐blue images results in measurement accuracy that did not differ between the two reading modes. On the other hand, the scanner uniformity and temporal stability, the long‐term stability of the film readings and the dynamic range is superior using the reflection mode. The dynamic range of dose measurements can be extended up to least using the alternative color channels by both reading techniques. Similar backscattering dose factors close to high inhomogeneities were found using both scanning modes. In conclusion, the use of reflection scanning mode of MD55 films was superior to the traditionally used transmission mode.
Proximal femur segmentation in conventional pelvic x ray
Authors: Pilgram Roland , Walch Claudia , Kuhn Volker , Schubert Rainer , Staudinger Roland
Published: June 2008

A solid and accurate proximal femur segmentation technique using the popular active shape model (ASM) is proposed. For generating an optimal shape prior, the minimum description length, based on 200 supervised manual segmented proximal femur shapes, is used. The segmentation is based on a coarse to fine scaling technique including a profile scale space method. The segmentation results are compared using an optimal defined initial pose and a pose based on a registration technique. Using ideal template initialization, 95% of the shapes have been recovered exactly (average point‐to‐point errorpixels, average point‐to‐boundary errorpixels). Using a template‐based initialization based on a registration technique, a successful segmentation rate ofis achieved, with an average point‐to‐point errorpixels, and an average point‐to‐boundary errorpixels. With an adequate template initialization and an improved ASM, this method seems to provide an accurate tool for segmentation of the proximal femur shapes on conventional hip overview x‐ray images.
Vision 20/20: Increased image resolution versus reduced radiation exposure
Authors: Ritman Erik L.
Published: June 2008

This is a review of methods, currently and potentially, available for significantly reducing x‐ray exposure in medical x‐ray imaging. It is stimulated by the radiation exposure implications of the growing use of helical scanning, multislice, x‐ray computed tomography for screening, such as for coronary artery atherosclerosis and cancer of the colon and lungs. Screening requires high‐throughput imaging with high spatial and contrast resolution to meet the need for high sensitivity and specificity of detection and classification of specific imaged features. To achieve this goal beyond what is currently available with x‐ray imaging methods requires increased x‐ray exposure, which increases the risk of tissue damage and ultimately cancer development. These consequences limit the utility of current x‐ray imaging in screening of at‐risk subjects who have not yet developed the clinical symptoms of disease. Current methods for reducing x‐ray exposure in x‐ray imaging, mostly achieved by increasing sensitivity and specificity of the x‐ray detection process, may still have potential for an up‐to‐tenfold decrease. This could be sufficient for doubling the spatial resolution of x‐ray CT while maintaining the current x‐ray exposure levels. However, a spatial resolution four times what is currently available might be needed to adequately meet the needs for screening. Consequently, for the proposed need to increase spatial resolution, an additional order of magnitude of reduction of x‐ray exposure would be needed just to keep the radiation exposure at current levels. This is conceivably achievable if refraction, rather than the currently used attenuation, of x rays is used to generate the images. Existing methods that have potential for imaging the consequences of refracted x ray in a clinical setting are (1) by imaging the edge enhancement that occurs at the interfaces between adjacent tissues of different refractive indices, or (2) by imaging the changes in interference patterns resulting from moving grids which alter the refraction of x rays, that have passed through the body, in a predictable fashion, and (3) theoretically, by an image generated from the change in time‐of‐flight of x‐ray photons passing through the body. Imaging phase shift or change in time‐of‐flight, rather than attenuation, of x‐ray photons through tissues presents formidable technological problems for whole‐body 3D imaging. However, if achievable in a routine clinical setting, these approaches have the potential for greatly expanding the use of x‐ray imaging for screening. This overview examines the increased contrast resolution and reduced radiation exposure that might be achievable by the above‐mentioned methods.
MLC quality assurance using EPID: A fitting technique with subpixel precision
Authors: Mamalui‐Hunter Maria , Li Harold , Low Daniel A.
Published: June 2008

Amorphous silicon based electronic portal imaging devices (EPIDs) have been shown to be a good alternative to radiographic film for routine quality assurance (QA) of multileaf collimator (MLC) positioning accuracy. In this work, we present a method of acquiring an EPID image of a traditional strip‐test image using analytical fits of the interleaf and leaf abutment image signatures. After exposure, the EPID image pixel values are divided by an open field image to remove EPID response and radiation field variations. Profiles acquired in the direction orthogonal to the leaf motion exhibit small peaks caused by interleaf leakage. Gaussian profiles are fitted to the interleaf leakage peaks, the results of which are, using multiobjective optimization, used to calculate the image rotational angle with respect to the collimator axis of rotation. The relative angle is used to rotate the image to align the MLC leaf travel to the image pixel axes. The leaf abutments also present peaks that are fitted by heuristic functions, in this case modified Lorentzian functions. The parameters of the Lorentzian functions are used to parameterize the leaf gap width and positions. By imaging a set of MLC fields with varying gaps forming symmetric and asymmetric abutments, calibration curves with regard to relative peak height (RPH) versus nominal gap width are obtained. Based on this calibration data, the individual leaf positions are calculated to compare with the nominal programmed positions. The results demonstrate that the collimator rotation angle can be determined as accurate as . A change in MLC gap width of leads to a change in RPH of about 10%. For asymmetrically produced gaps, a MLC leaf gap width change causes 0.2 pixel peak position change. Subpixel resolution is obtained by using a parameterized fit of the relatively large abutment peaks. By contrast, for symmetrical gap changes, the peak position remains unchanged with a standard deviation of 0.05 pixels, or . A trial run of 36 test images, each with gap widths varying from 0.4 to , were used to analyze 8640 abutments. The leaf position variations were detected with a precision of at a 95% confidence level, with a mean of and a standard deviation of . The proposed method is robust and minimizes the effect of image noise and pixel size and may help physicists to establish reliable and reasonable action levels in routine MLC QA.
A moving slanted‐edge method to measure the temporal modulation transfer function of fluoroscopic systems
Authors: Friedman S. N. , Cunningham I. A.
Published: June 2008

Lag in fluoroscopic systems introduces a frame‐averaging effect that reduces measurements of image noise and incorrectly inflates measurements of the detective quantum efficiency (DQE). A correction can be implemented based on measurements of the temporal modulation transfer function (MTF). We introduce a method of measuring the temporal MTF under fluoroscopic conditions using a moving slanted edge, a generalization of the slanted‐edge method used to measure the (spatial) MTF, providing the temporal MTF of the entire imaging system. The method uses a single x‐ray exposure, constant edge velocity, and assumes spatial and temporal blurring are separable. The method was validated on a laboratory x‐ray image intensifier (XRII) system by comparison with direct measurements of the XRII optical response, showing excellent agreement over the entire frequency range tested . With proper access to linearized data and continuous fluoroscopy, this method can be implemented in a clinical setting on both XRII and flat‐panel detectors. It is shown that the temporal MTF of the CsI‐based validation system is a function of exposure rate. The rising‐edge response showed more lag than the falling edge, and the temporal MTF decreased with decreasing exposure rate. It is suggested that a small‐signal approach, in which the range of exposure rates is restricted to a linear range by using a semitransparent moving edge, would be appropriate for measuring the DQE of these systems.
Radio‐frequency ablation electrode displacement elastography: A phantom study
Authors: Bharat Shyam , Varghese Tomy , Madsen Ernest L. , Zagzebski James A.
Published: June 2008

This article describes the evaluation of a novel method of tissue displacement for use in the elastographic visualization of radio‐frequency (rf) ablation‐induced lesions. The method involves use of the radio‐frequency ablation electrode as a displacement device, which provides localized compression in the region of interest. This displacement mechanism offers the advantage of easy in vivo implementation since problems such as excessive lateral and elevational displacements present when using external compression are reduced with this approach. The method was tested on a single‐inclusion tissue‐mimicking phantom containing a radio‐frequency ablation electrode rigidly attached to the inclusion center. Full‐frame rf echo signals were acquired from the phantom before and after electrode displacements ranging from 0.05 to 0.2 mm. One‐dimensional cross‐correlation analysis between pre‐and postcompression signals was used to measure tissue displacements, and strains were determined by computing the gradient of the displacement. The strain contrast, contrast‐to‐noise ratio, and signal‐to‐noise ratio were estimated from the resulting strain images. Comparisons are drawn between the elastographically measured dimensions and those known a priori for the single‐inclusion phantom. Electrode displacement elastography was found to slightly underestimate the inclusion dimensions. The method was also tested on a second tissue‐mimicking phantom and on in vitro rf‐ablated lesions in canine liver tissue. The results validate previous in vivo findings that electrode displacement elastography is an effective method for monitoring rf ablation.
Evaluation of linear accelerator performance standards using an outcome oriented approach
Authors: Rangel Alejandra , Ploquin Nicolas , Kay Ian , Dunscombe Peter
Published: June 2008

Radiation therapy, along with other branches of medicine, is moving towards a firmer basis in evidence to optimally utilize resources. As new treatment technology and strategies place greater demands on quality assurance resources, the need to objectively evaluate equipment and process performance standards from the perspective of predicted clinical impact becomes more urgent. This study evaluates the appropriateness of recommended quality control tolerance and action levels for linear accelerators based on the calculated dosimetric impact of suboptimal equipment performance. A method is described to quantify the dosimetric changes, as reflected by the changes in the outcome surrogate, equivalent uniform dose (EUD), of machine performance deviations from the optimal, specifically in the range of tolerance and action levels promulgated by the Canadian Association of Provincial Cancer Agencies (CAPCA). Linear accelerator performance deviations were simulated for the treatment of prostate, breast, lung, and brain using 3D conformal techniques, and the impact evaluated in terms of the changes in the EUD of the target volumes and two principal organs at risk (OARs) per site. The eight key performance characteristics examined are: Output constancy, beam flatness, gantry angle, collimator angle, field size indicator, laser alignment (three directions) and, by inference, the optical distance indicator. Currently accepted CAPCA tolerance levels for these eight performance characteristics are shown to maintain average EUD deviations to within 2% for the targets and for the OARs. However, within the 2% or range, the recommended tolerance levels are found to have markedly different effects on the EUDs of the structures of interest.
Digital tomosynthesis of the chest for lung nodule detection: Interim sensitivity results from an ongoing NIH‐sponsored trial
Authors: Dobbins James T. , McAdams H. Page , Song Jae‐Woo , Li Christina M. , Godfrey Devon J. , DeLong David M. , Paik Sang‐Hyun , Martinez‐Jimenez Santiago
Published: June 2008

The authors report interim clinical results from an ongoing NIH‐sponsored trial to evaluate digital chest tomosynthesis for improving detectability of small lung nodules. Twenty‐one patients undergoing computed tomography (CT) to follow up lung nodules were consented and enrolled to receive an additional digital PA chest radiograph and digital tomosynthesis exam. Tomosynthesis was performed with a commercial CsI/‐Si flat‐panel detector and a custom‐built tube mover. Seventy‐one images were acquired in 11 s, reconstructed with the matrix inversion tomosynthesis algorithm at 5‐mm plane spacing, and then averaged (seven planes) to reduce noise and low‐contrast artifacts. Total exposure for tomosynthesis imaging was equivalent to that of 11 digital PA radiographs (comparable to a typical screen‐film lateral radiograph or two digital lateral radiographs). CT scans (1.25‐mm section thickness) were reviewed to confirm presence and location of nodules. Three chest radiologists independently reviewed tomosynthesis images and PA chest radiographs to confirm visualization of nodules identified by CT. Nodules were scored as: definitely visible, uncertain, or not visible. 175 nodules (diameter range 3.5–25.5 mm) were seen by CT and grouped according to size: , 5–10, and . When considering as true positives only nodules that were scored definitely visible, sensitivities for all nodules by tomosynthesis and PA radiography were and , respectively, . Digital tomosynthesis showed significantly improved sensitivity of detection of known small lung nodules in all three size groups, when compared to PA chest radiography.
Resource Letter GW-2: Global Warming
Authors: Mastrandrea Michael D. , Schneider Stephen H.
Published: June 2008

This Resource Letter provides a guide to the literature on human-induced climate change, also known as global warming [Resource Letter GW-1: Global Warming, John W. Firor, Am. J. Phys. 62, 490–495 (1994)]. After an introductory overview, journal articles, books, and websites are cited for the following topics: the greenhouse effect and radiative forcing, detection and attribution of human-induced climate change, carbon cycle feedbacks, paleoclimate, climate models and modeling uncertainties, projections of future climate change and climate impacts, and mitigation and adaptation policy options.
Planets on the table: A laboratory experiment on radiation and planetary effective-temperature concepts
Authors: Karabanov Oleksandr , St. John James C. , Chameides William
Published: June 2008

A new undergraduate laboratory experiment demonstrates radiation laws and their applications to climatology and environmental science. The experiment emphasizes the planetary energy budget and effective-temperature concepts. A close look at “planets on the table” brings some unanticipated results that challenge students to think critically, to interpret the results of measurements, and to come to valid scientific conclusions.
Preparing physics graduate students to be educators
Authors: Price Edward , Finkelstein Noah
Published: June 2008

We discuss two efforts that support the preparation of graduate students for their roles as professional physicists, particularly in the areas of teaching and education research. The Preparing Future Physicists program and the Teaching and Learning Physics course are mutually supportive, address broader graduate roles, and support the development of physics education research. Students’ participation in these activities increases their mastery of physics, develops their interest in education and teaching, and engages them in research projects in physics education. We describe these efforts and identify critical features of their successes.
Relativistic transformation of perpendicular velocity components from the constancy of the speed of light
Authors: Hu Ben Yu-Kuang
Published: June 2008

Mermin has derived the relativistic addition of the parallel components of velocity directly from the constancy of the speed of light. In this note the derivation is extended to the perpendicular components of the velocity.
Point Mutation in the Group B Streptococcal
pbp2x
Gene Conferring Decreased Susceptibility to β-Lactam Antibiotics
Authors: Dahesh Samira , Hensler Mary E. , Van Sorge Nina M. , Gertz Robert E. , Schrag Stephanie , Nizet Victor , Beall Bernard W.
Published: June 2008

Beta-lactam antibiotics (BLAs) are the first-line agents used against group B streptococci (GBS) infection. A clonal set of four independent, invasive GBS isolates with elevated MICs to BLAs were identified that shared a
pbp2x
mutation (Q557E) corresponding to a resistance-conferring pneumococcal mutation. BLA sensitivity was restored through allelic replacement or complementation with the wild-type
pbp2x
.
Constitutive Activation of the PrfA Regulon Enhances the Potency of Vaccines Based on Live-Attenuated and Killed but Metabolically Active
Listeria monocytogenes
Strains
Authors: Lauer Peter , Hanson Bill , Lemmens Edward E. , Liu Weiqun , Luckett William S. , Leong Meredith L. , Allen Heather E. , Skoble Justin , Bahjat Keith S. , Freitag Nancy E. , Brockstedt Dirk G. , Dubensky Thomas W.
Published: June 2008

Recombinant vaccines derived from the facultative intracellular bacterium
Listeria monocytogenes
are presently undergoing early-stage clinical evaluation in oncology treatment settings. This effort has been stimulated in part due to preclinical results that illustrate potent activation of innate and adaptive immune effectors by
L. monocytogenes
vaccines, combined with efficacy in rigorous animal models of malignant and infectious disease. Here, we evaluated the immunologic potency of a panel of isogenic vaccine strains that varied only in
prfA
. PrfA is an intracellularly activated transcription factor that induces expression of virulence genes and encoded heterologous antigens (Ags) in appropriately engineered vaccine strains. Mutant strains with PrfA locked into a constitutively active state are known as PrfA* mutants. We assessed the impacts of three PrfA* mutants, G145S, G155S, and Y63C, on the immunologic potencies of live-attenuated and photochemically inactivated nucleotide excision repair mutant (killed but metabolically active [KBMA]) vaccines. While PrfA* substantially increased Ag expression in strains grown in broth culture, Ag expression levels were equivalent in infected macrophage and dendritic cell lines, conditions that more closely parallel those in the immunized host. However, only the
prfA
(
G155S
) allele conferred significantly enhanced vaccine potency to KBMA vaccines. In the KBMA vaccine background, we show that PrfA*(G155S) enhanced functional cellular immunity following an intravenous or intramuscular prime-boost immunization regimen. These results form the basis of a rationale for including the
prfA
(
G155S
) allele in future live-attenuated or KBMA
L. monocytogenes
vaccines advanced to the clinical setting.
An Iron-Binding Protein, Dpr, Decreases Hydrogen Peroxide Stress and Protects
Streptococcus pyogenes
against Multiple Stresses
Authors: Tsou Chih-Cheng , Chiang-Ni Chuan , Lin Yee-Shin , Chuang Woei-Jer , Lin Ming-T. , Liu Ching-Chuan , Wu Jiunn-Jong
Published: June 2008

Streptococcus pyogenes
does not produce catalase, but it can grow in aerobic environments and survive in the presence of peroxide. One of the stress proteins of this organism, peroxide resistance protein (Dpr), has been studied to examine its role in resistance to hydrogen peroxide, but the protective mechanism of Dpr is not clear. The aim of this study was to characterize the
dpr
gene and its role in dealing with different stresses. A
dpr
deletion mutant was constructed by double-crossover mutagenesis. The
dpr
mutant was more sensitive to H
2
O
2
, and complementation could partially restore the defect in the mutant. Pretreatment with the iron chelator deferoxamine mesylate rescued the survival activity of the mutant under oxidative stress conditions. The
dpr
mutant also showed a low survival rate in the long-term stationary phase, when it was treated with extreme acids, and under alkaline pH conditions compared to the wild-type strain. The growth of the
dpr
mutant was slower than that of the wild-type strain in iron-limiting conditions. The
dpr
mutant showed high sensitivity to iron and zinc but not to manganese, copper, nickel, and calcium. Recombinant Dpr protein was purified and showed iron-binding activity, whereas no DNA-binding activity was found. These data indicate that an iron-binding protein, Dpr, provides protection from hydrogen peroxide stress by preventing the Fenton reaction, and Dpr was identified as a novel stress protein that protects against several stresses in group A streptococci.
Shiga Toxin 2 Causes Apoptosis in Human Brain Microvascular Endothelial Cells via C/EBP Homologous Protein
Authors: Fujii Jun , Wood Katie , Matsuda Fumiko , Carneiro-Filho Benedito A. , Schlegel Keilo H. , Yutsudo Takashi , Binnington-Boyd Beth , Lingwood Clifford A. , Obata Fumiko , Kim Kwang S. , Yoshida Shin-ichi , Obrig Tom
Published: June 2008

Shiga toxin 1 (Stx1) and Stx2 produced byEscherichia coliO157 are known to be cytotoxic to Vero and HeLa cells by inhibiting protein synthesis and by inducing apoptosis. In the present study, we have demonstrated that 10 ng/ml Stx2 induced DNA fragmentation in human brain microvascular endothelial cells (HBMEC), with cleavage activation of caspase-3, -6, -8, and -9. A microarray approach used to search for apoptotic potential signals in response to Stx2 revealed that Stx2 treatment induced a marked upregulation of C/EBP homologous protein (CHOP)/growth arrest and DNA damage-inducible protein 153 (GADD153). Increased CHOP expression was dependent on enzymatically active Stx1. Knockdown of CHOP mRNA reduced the activation of caspase-3 and prevented apoptotic cell death. These results suggest that Stx2-induced apoptosis is mediated by CHOP in HBMEC and involves activation of both the intrinsic and extrinsic pathways of apoptosis.
Temperature Preference and Avoidance Responses of the Crayfish, Orconectes obscurus, and Associated Statistical Problems
Authors: Mathur Dilip , Schutsky Robert M. , Purdy Jr. Edmund J.
Published: June 2008

Acute temperature selection and avoidance responses of the crayfish, Orconectes obscurus, acclimated at field collection temperatures of 1.5–26.0 °C and determined in a spatial thermal gradient, were similar to those noted for fishes. Acclimation temperature was positively correlated with the acute preferred and avoided temperatures; both were several degrees higher than the acclimation temperature. A large proportion of the total variance in these data was unexplained. Most variable responses occurred at low acclimation temperatures. The estimated final preferred temperature ranged from 29.8 to 33.9 °C depending upon the method of calculation. Methods of estimating final preferenda from acute tests are considered arbitrary due to statistical problems and the associated high variability. Statistical problems were also noted in the determination of avoidance temperatures of crayfish due to nonindependence of observations on the same organism. No differences were noted (P < 0.05) between the preferred or avoided temperatures when the direction of field temperatures was rising or falling. A statistical comparison of the new and published data on this species revealed general similarities, particularly over an acclimation temperature range of 18.0–30.0 °C. The analysis minimizes the importance of site-specific studies on this species using the current acute testing methods.Key words: crayfish, temperature preference, avoidance, populational variation, statistics, experimental and statistical problems
Decline of Lake Herring (Coregonus artedii) In Lake Superior: An Analysis of the Wisconsin Herring Fishery, 1936–78
Authors: Selgeby James H.
Published: June 2008

Annual harvests of lake herring (Coregonus artedii) in American waters of Lake Superior declined from an average of 2 million kg in 1936–62 to less than 25 000 kg in 1978. Analysis of commercial fishing records revealed that the sequential overexploitation of discrete unit stocks caused the collapse of the herring population in Wisconsin waters. In each of six major spawning areas, catch exceeded the productive capacity of the stock and the stock failed. Because stocks in the six areas were exploited sequentially, mostly in groups of two or three simultaneously, the demise of the stocks was not readily apparent until the last two failed in the early 1960s. After the collapse of the last major spawning stock, the fishery dwindled but may have continued to overexploit the remaining small stocks. The residual populations were apparently able only to replace themselves. Some form of density-independent mortality was apparently operating to prevent their recovery during the 1960s and 1970s.Key words: lake herring, overfishing, Lake Superior
Early Trend Determination of Organochlorine Contamination from Residue Ratios in the Sea Lamprey (Petromyzon marinus) and its Lake Whitefish (Coregonus clupeaformis) Host
Authors: Kaiser Klaus L. E.
Published: June 2008

A detailed statistical evaluation of the levels of organochlorine contaminants in sea lamprey (Petromyzon marinus) and simultaneously caught lake whitefish (Coregonus clupeaformis) from the northern parts of Lakes Huron and Michigan is described. The analysis of residue ratios, both within each species and between, allows an immediate recognition of rising and falling trends of contamination with a high degree of confidence. This improvement over the conventional method of monitoring one species over several years is accomplished with comparatively little effort in sampling and chemical contaminant analysis. The described technique exploits the unique biological relationship of the lamprey and its host and is also based on the significantly shorter lifespan of the (adult) lamprey compared to that of the host. Rising trends in PCB and DDE contamination and declining trends for the levels of DDT, dieldrin, endrin, chlordane, hexachlorobenzene, heptachlorepoxide, and α-hexachlorocyclohexane were observed in 1978, the year of collection.Key words: organochlorine, contamination, trend, ratio, Petromyzon marinus, Coregonus clupeaformis
Seaward Movement of Coho Salmon (Oncorhynchus kisutch) Fry in Carnation Creek, an Unstable Coastal Stream in British Colombia
Authors: Hartman G. F. , Andersen B. C. , Scrivener J. C.
Published: June 2008

The seaward movement of coho (Oncorhynchus kisutch) fry was monitored over a 10-yr period as a part of a major watershed study. The time period over which downstream movement took place varied widely during different years of study. Coho fry moved seaward earlier, and terminated the main period of movement earlier, following winters in which stream temperatures were warmer. It is presumed that they underwent more rapid development during winters in which stream temperatures were relatively high. Winter stream temperatures were primarily dependent on air temperatures. During seaward movement daily numbers fluctuated widely. Peaks of movement were coincident with or slightly before freshet peaks. In 94 of 122 cases (77%) the number of fry moving seaward during the night of peak discharge, or during the night before, was higher than in any of the three preceding nights. Movement in these cases may have been initiated by rainfall or falling water temperature or a combination of both. Aggressive behavior among coho fry is considered to be an underlying cause of seaward movement. In Carnation Creek, particularly in the early part of the period of seaward movement, the effects of such social behavior on movement patterns may be masked by the effect of freshets and related conditions. By autumn the number of fry remaining in the stream ranged from 9000 to 13 000 over the 10-yr study. Much of the downward adjustment to this resident fry population size occurred after the most active period of seaward movement.Key words: coho fry, social behavior, seaward movement, stream ecology, coho management
Statistical Determination of Data Requirements for Assessment of Lake Restoration Programs
Authors: Trautmann Nancy Morton , McCulloch Charles E. , Oglesby Ray T.
Published: June 2008

To test the effectiveness of lake restoration programs, monitoring must be carried out both before and after any change is made. Statistical techniques are presented for calculation of these sampling requirements both for individual lakes and for groups of lakes analyzed collectively. Illustration of these techniques is made using data on productivity of New York State's Finger Lakes before and after the state ban on phosphate detergents. Existing pre-ban data on mean summer phytoplankton standing crop are shown to be insufficient for conclusive evidence of a post-ban productivity change in individual lakes no matter how many years of post-ban data could be obtained. When the lakes are analyzed as a group rather than individually, however, the conclusion is reached that there is a probability of only 0.7% that a chlorophyll drop at least as large as the one observed would have occurred without the effect of the phosphate detergent ban. Use of power calculations before sampling is begun will help to maximize the efficiency of data collection efforts in lake restoration programs.Key words: lake sampling design, statistical analysis, summer chlorophyll, data requirements, lake restoration, eutrophication
Stock Identification of Sockeye Salmon (Oncorhynchus nerka) with Scale Pattern Recognition
Authors: Cook Rodney C.
Published: June 2008

The non-Gaussian density functions underlying polynomial discrimant functions are employed in a classification scheme designed for sockeye salmon (Oncorhynchus nerka). A leaving-one-out approach is used to estimate the smoothing parameters in the density functions and to obtain nearly unbiased estimates of expected actual error rates in the classification scheme. The result is that all available observations of known origin may be used to determine the discriminant rule and estimate classification error rates. These are needed to obtain point estimates of the proportions of subpopulations present in areas of intermingling. Several additional improvements over the polynomial discriminant method are noted. The scheme is applied to scale measurement data of sockeye salmon from Bristol Bay, the Gulf of Alaska, and the Kamchatka Peninsula.Key words: stock identification, discriminant analysis, sockeye salmon
Paleolimnological Evidence of Early Eutrophication in Lake Erie
Authors: Harris Graham P. , Vollenweider Richard A.
Published: June 2008

Data obtained on diatom remains found in a core taken from the central Basin of Lake Erie have allowed the reinterpretation of the observed changes in the lake in the light of the existing literature, new data, and some new ideas on the operation of planktonic ecosystems. The basic conclusion is that Lake Erie has exhibited mesotrophic to eutrophic conditions, at least in parts, since approximately 1850, and that the initial disturbance to the lake's metabolism was the most important one. In common with other planktonic ecosystems, Lake Erie exhibits some long-term fluctuations which make the interpretation of long-term trends very difficult. Events in the basin over the last 50 to 60 years must be viewed in the light of these long-term fluctuations and must be interpreted with care.Key words: paleolimnology, eutrophication, plankton, ecosystems, Lake Erie, metabolism, phosphorus, loadings, fluctuations
Geodock (Panope generosa: Bivalvia) Age as Determined by Internal Growth Lines in the Shell
Authors: Shaul Warren , Goodwin Lynn
Published: June 2008

Geoduck (Panope generosa) age was determined by counting internal growth lines in the hinge plates of the shells. Several experiments substantiated the hypothesis that one growth line is deposited every year. Growth line deposition was found to occur during the winter.Key words: age, geoducks, Bivalvia, growth lines
Ammonia Excretion in Corophium volutator: Using an Automated Method
Authors: Hawkins Christopher M. , Keizer Paul D.
Published: June 2008

Rates of ammonia excretion for Corophium volutator were determined for 99 individuals using an automated method. The method allowed rapid and precise determination of excretion rates for single animals as a function of time. Excretion rates for Corophium ranged from 0.66 to 24.4 ng-atm∙mg−1∙h−1 for animals weighing 0.10–1.87 mg dry weight.Key words: ammonia, excretion rate, Corophium volutator
Methemoglobin Levels in Channel Catfish, Ictalurus punctatus, Exposed to Nitrite and Tricaine Methanesulfonate
Authors: Huey D. W. , Beitinger T. L.
Published: June 2008

Channel catfish (Ictalurus punctatus) were exposed for 24 h to one of the following: 4.0 mg/L nitrite, 4.0 mg/L nitrite + 40 mg/L TMS-222, 40 mg/L TMS-222 and control in which neither chemical was added. Methemoglobin concentrations reported as percentage of total hemoglobin equalled mean ± SD (n) 65.9 ± 10.8 (10), 45.7 ± 9.1 (15), 13.7 ± 5.9 (26), and 2.2 ± 0.4 (10) in the four groups, respectively. Mean methemoglobin in each o f the three treatment groups was significantly greater than controls and significantly different among each other. As expected, nitrite-induced methemoglobinemia was slightly reduced in the presence of TMS-222 for this short-term exposure. The most important finding was that catfish exposed to TMS-222 had methemoglobin levels 6 times greater than those of controls.
Growth Rates and Protein Turnover in Atlantic Cod,Gadus morhua
Authors: Houlihan D. F. , Hall S. J. , Gray C. , Noble B. S.
Published: June 2008

Atlantic cod, Gadus morhua, were maintained on different ration levels or starved to produce a variety of growth rates. The in vivo rates of protein synthesis and degradation were determined for the whole fish and various tissues. As ration level, and hence growth rates, increased, both whole-animal protein synthesis and degradation rates increased linearly; growth occurred because of the preponderance of synthesis over degradation. On average, a 300-g cod growing at 1.0%∙d−1synthesised 1.25 g of protein with 0.4 g of this protein remaining as growth. The proportion of total protein synthesis which was retained as growth increased with increasing growth rate; at a maximum growth rate of 2%∙d−1, over 40% of the protein synthesised was retained as growth. The ranking of the tissues in terms of fractional rates of protein synthesis was liver > gills > intestine > spleen > ventricle > stomach > gonads > white muscle. The white muscle, gills, liver, stomach, spleen, and ventricle all showed similar patterns of increased protein synthesis with increased growth rate. The white muscle has the highest efficiency of retention of protein and accounts for 40% of the total protein accretion per day. In starving fish there was a constant level of protein synthesis, irrespective of the rate of weight loss. However, degradation rates increased in the whole animal and in white muscle as the rate of weight loss increased.
The Fowlkes–Mallows Statistic and the Comparison of Two Independently Determined Dendrograms
Authors: Nemec A. F. L. , Brinkhurst R. O.
Published: June 2008

When interpreting the results of a cluster analysis, it is important to understand why specific clustering patterns arise. Comparison of a "dependent" dendrogram with a second, independently determined "covariate" dendrogram (i.e. one that is based solely on information provided by various explanatory variables) is a simple way of investigating the role played by the covariates. The Fowlkes–Mallows statistic, which is a measure of the degree of similarity between two dendrograms, can be used to test the null hypothesis that two dendrograms are unrelated. We show that the Fowlkes–Mallows test can be usefully employed in the systematic comparison of a dependent dendrogram and covariate dendrogram. Since the test is nonparametric, it is applicable to a wide range of problems. As an illustrative example, a species abundance matrix for several benthic communities is subjected to a standard cluster analysis, and the resultant (dependent) dendrogram is compared with a clustering based on the geographic location of the communities. At least some of the clustering seen in the dependent dendrogram can be attributed to the geographic proximity of the stations.
Thermal Significance of the Topographical Distribution of Blubber in Ringed Seals (Phoca hispida)
Authors: Ryg Morten , Smith Thomas G. , Øritsland Nils Are
Published: June 2008

The distribution of blubber in ringed seals (Phoca hispida) and relationships between surface area, body mass, and linear dimensions are described. The blubber was distributed in such a way that the ratio of blubber thickness to body radius is nearly constant over the body, maximizing the available blubber for insulation. The hind part of the body has a higher thickness to radius ratio and is thus "overinsulated." During periods of mass loss, fat is lost fastest from this overinsulated region, thus reducing the negative thermal effects of the fat loss. We present formulae for calculating body surface area and an effective, or "equivalent blubber thickness," for calculations of heat loss and suggest that these formulae are independent of size and shape. By combining these equations, we arrive at a general formula for calculating a lower limit for heat loss from marine mammals. According to this formula, thermal stability can be maintained when blubber is lost if mass is simultaneously lost from the body core.
Relative Selectivities of Miller High-Speed Samplers and Light Traps for Collecting Ichthyoplankton
Authors: Gregory R. S. , Powles P. M.
Published: June 2008

Comparative studies on the relative selectivities of Miller high-speed samplers and light traps in Chemung Lake, Ontario, were made over 29 "site-nights" from May 13 to June 25, 1982. Yellow perch (Perca flavescens), Iowa darter (Etheostoma exile), and pumpkinseed sunfish (Lepomis gibbosus) constituted 97.2% of the 4376 specimens collected. A percent similarity index indicated a high uniformity in the size and species composition of the catch (~70% for much of the study); similarity was least on the earliest sample date (May 13, 3.5%). Smaller darters (<6.0 mm total length) were excluded from the Miller sampler catch. We suggest that extrusion of prolarval and early postlarval darters through the tow nets is responsible for low percent similarity index values in early May. We propose that investigators consider a mixture of passive and active sampling techniques to alleviate existing selectivity biases.
Underwater Spectral Attenuation and Its Effect on the Maximum Depth of Angiosperm Colonization
Authors: Chambers P. A. , Prepas E. E.
Published: June 2008

Data collected from 23 Alberta lakes and literature values for 45 other north temperate lakes were used to develop regression models to evaluate the effect of underwater light quality on the maximum depth of angiosperm colonization. Unlike most north temperate lakes, eutrophic Alberta lakes have unusually low levels of dissolved colour and, as a result, transmit blue light particularly well. Comparison of regression equations relating the maximum depth of angiosperm colonization (zc) and Secchi depth (D) for lakes with low colour [Formula: see text] and with high colour [Formula: see text] showed that for any Secchi depth, aquatic angiosperms colonized to greater depths in lakes with low colour. These results demonstrate that light quality as well as light quantity determine the maximum depth of angiosperm colonization in lakes. Regional differences in the relation between zc and Secchi depth may therefore be due to variations in the underwater light spectrum.
Growth of Juvenile Coho Salmon (Oncorhynchus kisutch) off Oregon and Washington, USA, in Years of Differing Coastal Upwelling
Authors: Fisher J. P. , Pearcy W. G.
Published: June 2008

Estimated growth rates, condition, and stomach fullness of juvenile coho salmon (Oncorhynchus kisutch) caught in the ocean in early summer, when mortality was most variable, were as high in 1983 and 1984, years of very low survival and low early upwelling, as in 1981, 1982, and 1985, years of higher survival and higher early upwelling. Chronic food shortage leading to starvation, poor condition, or slow growth apparently was not the cause of the increased mortality of juvenile coho salmon in 1983 and 1984. Survival of juvenile coho salmon was positively correlated with purse seine catches of fish in June and with early summer upwelling, 1981–85. Hence, year-class success probably was determined early in the summer, soon after most juvenile coho salmon entered the ocean. Spacing of the first five ocean circuli, which was positively correlated with growth rate, was not significantly different for fish caught early in the summer and those caught late in the summer, suggesting that growth rate selective mortality in the ocean was not strong. The increase in mortality in 1983 and 1984 may have been caused by increased predation on juvenile coho salmon due to decreased numbers of alternative prey for predators.
Accumulation of Cadmium by Rainbow Trout, Salmo gairdneri, during Extended Exposure
Authors: Giles Michael A.
Published: June 2008

Adult rainbow trout, Salmo gairdneri, were exposed to 3.6 and 6.4 μg Cd/L for 178 d. Cadmium accumulated most rapidly in gill tissue which became saturated at levels 100-fold higher than controls within 24 and 52 d in the high- and low-metal exposures, respectively. Liver cadmium increased 250- to 400-fold over the test period but accumulation exhibited a plateau between 52 and 129 d followed by a rapid rise by 178 d. Kidney cadmium increased consistently throughout the test period to levels approximately 50- to 100-fold higher than control values. Cadmium in the gut and skin increased 10- and 5-fold, respectively, while no increase was recorded in white muscle. A maximum of 2.1% of the cadmium available in a commercial diet (0.2 μg Cd/g dry food} was accumulated in control fish. Although cadmium was not detected in the urine, urinary zinc excretion was elevated in trout exposed to 6.4 μg Cd/L such that 7 mol of zinc was excreted per 1 mol of cadmium accumulated during the initial 24 d of exposure. The whole-body burden of cadmium increased linearly with time in both treatments with a time constant of 0.366 and 0.554%/d for trout exposed to 3.6 and 6.4 μg Cd/L, respectively.
DNA-Level Polymorphism as a Tool in Fisheries Science
Authors: Hallerman Eric M. , Beckmann Jacques S.
Published: June 2008

Several methods for the visualization of genetic polymorphisms at the nucleic acid level have been developed. Such polymorphisms promise to be exceedingly numerous, and may form the basis for a number of scientific and practical applications in fisheries science. An expanded number of genetic markers should increase the statistical power of marker-based studies in population genetics, for example, improving the sensitivity of biological stock assessments and of studies assessing the impact of stocking programs upon natural populations. Utilization of such genomic markers could contribute to the rapid elaboration of piscine genomic maps and to development of markers for health- and production-related traits in fishes.
Uncoupling of Somatic and Otolith Growth Rates in Arctic Char (Salvelinus alpinus) as an Effect of Differences in Temperature Response
Authors: Mosegaard Henrik , Svedäng Henrik , Taberman Kjell
Published: June 2008

Experiments were conducted to study the effect of temperature, fish size, and somatic growth rate on mean daily otolith growth rate in Arctic char (Salvelinus alpinus) fry fed maximum rations. Long-term experiments at two different temperatures (8 and 13 °C) showed exponential relationships between otolith weight and fish wet weight, with the exponent of wet weight for the higher temperature being significantly higher than for the lower temperature. Increasing exponents at each sampling date indicated a difference in growth rates of the char and its otoliths. Short-term experiments showed that specific growth rate of the fry at six different temperatures was that of an optimum curve whereas the otolith growth rate continued to increase with increasing temperatures. A clear uncoupling between otolith growth rate and fish growth rate was demonstrated whereas temperature and fish wet weight modeled otolith growth rate reasonably well. It was found that otolith growth rate expressed as daily increase in weight gave a model with better fit and higher generality than growth rate along various radii. Several examples of uncoupling between fish growth rate and otolith growth rate in the literature were reexamined, and an explanation of otolith growth rate in terms of a metabolic expression was suggested.