bluuebunny/crossref_metadata_2025 huggingface dataset:
The Development of Telegraphy, 1870–1900: A European Perspective on a World History Challenge
Authors: Wenzlhuemer Roland
Published: July 2007

This article puts forward that the study of so‐called information societies and of the interplay of information technology and society in general needs to be amended from a historical perspective. Only by looking back further than the 1960s can the concept of an information revolution be critically evaluated. I argue that the study of information societies must at least go back until the invention and spread of electric telegraphy which has brought about the detachment of telecommunication from transport and thus created a virtual space of information. The essay seeks to provide some initial empirical findings in order to facilitate the identification of regional case studies with different degrees of global connectivity. Statistical data from the ITU archives in Geneva has been collected and indexed in order to illustrate how different regions in Europe and the wider world developed in telegraphic terms between 1870 and 1900. It is hoped and anticipated that these initial findings will be refined and shall eventually provide the structural basis for detailed historical comparisons between regions with different points of connection.
African‐American Committee Chairs in U.S. State Legislatures*
Authors: D'Andra Orey Byron , Overby L. Marvin , Larimer Christopher W.
Published: July 2007

Objective. In this article, we explore whether African‐American state legislators have been able to translate election to office into positions of power, particularly as committee chairs.

Methods. We cull data from all state legislative chambers that contained a black legislator during two time periods, 1989 and 1999. In doing so, we compare the observed numbers of African‐American chairs with their expected numbers. We also examine each state's percentage of black chairs using multiple regression to determine what factors—political, partisan, institutional, cultural—influence the selection of black committee chairs.

Results. Overall, our descriptive analysis reveals that blacks are underrepresented as chairs. They are not, however, significantly underrepresented as chairs of the most important committees and they are generally overrepresented as chairs of committees with jurisdiction over social services. Our multivariate analyses show that the prevalence of black chairs is driven primarily by factors related to partisan control of legislative chambers and size of the black legislative delegation, and that these dynamics have changed over time.

Conclusion. Although the increase in African‐American state legislators has led to an increase in substantive leadership roles, these positions have been limited almost entirely to chambers where the black caucus is a critical element of a Democratic majority.
Slanted Objectivity? Perceived Media Bias, Cable News Exposure, and Political Attitudes*
Authors: Morris Jonathan S.
Published: July 2007

Objectives.This research explores the consequences of a fragmented television news audience. The recent proliferation of a wide array of television news sources has influenced the manner in which a large number of Americans get their information about politics and government. The political consequences of media fragmentation and the polarization of the U.S. television news audience are explored.

Methods.I analyze data on television news‐gathering habits and political attitudes collected from several surveys conducted by the Pew Research Center during the 2004 presidential election campaign.

Results.The Fox News Channel has been the main beneficiary of television news fragmentation by appealing to those individuals who have become disillusioned with what they perceive as a liberally‐biased mainstream media. The findings show that the Fox News audience has a distinct set of political attitudes regarding President Bush and his opposition. Evidence also indicates that the Fox News audience has distinct voting behavior patterns, even when controlling for party identification. Finally, the results illustrate that Fox News watchers have perceptions of political reality that differ from the rest of the television news audience.

Conclusions.The television news audience is divided along political lines. This division could contribute toward further political polarization among the U.S. mass public as the content of television news coverage of politics becomes less and less homogenized.
Leveling the Playing Field: Should Student Evaluation Scores be Adjusted?*
Authors: McPherson Michael A. , Jewell R. Todd
Published: July 2007

Objectives. Colleges and universities routinely use evaluation scores to assess the quality of an instructor's teaching for purposes of promotion and tenure and for merit‐raise allocations. This article attempts to identify the determinants of these scores, and to suggest ways that departments' numerical rankings of instructors might be adjusted.

Method. This article applies a feasible generalized least squares model to a panel of data from master's‐level classes.

Results. We find that instructors can “buy” better evaluation scores by inflating students' grade expectations. Also, the teaching experience of instructors has an impact on evaluation scores, but this effect is largely seen as an increase after tenure is granted. In addition, we find evidence of a bias against nonwhite faculty.

Conclusion. Our results suggest that an adjustment to the usual departmental rankings may be in order.
Structural and Dynamic Process Family Risk Factors: Consequences for Holistic Adolescent Functioning
Authors: Matjasko Jennifer L. , Grunden Leslie N. , Ernst Jody L.
Published: July 2007

This study utilized a dynamic cumulative family risk model to explain changes in adolescent functioning. We used a person‐centered approach to detect patterns of academic, emotional, and behavioral functioning and the stability of these patterns using two waves of the National Longitudinal Study of Adolescent Health (N= 10,173). Four adjustment profiles emerged at both time points. Although most (91%) adolescents remained in the same classifications at both waves, some experienced shifts in functioning. Changes in family process risk factors predicted these shifts in adjustment, whereas changes in structural risk factors predicted stable adjustment. We concluded that even short‐term changes in family processes are significant sources of risk for some adolescents.
Single Parenthood and Children’s Reading Performance in Asia
Authors: Park Hyunjoon
Published: July 2007

Using the data from Program for International Student Assessment, I examine the gap in reading performance between 15‐year‐old students in single‐parent and intact families in 5 Asian countries in comparison to the United States. The ordinary least square regression analyses show negligible disadvantages of students with a single parent in Hong Kong and Korea, once students’ demographic characteristics and socioeconomic background are held constant. Students in single‐parent families in Indonesia and Thailand outperform their peers in intact families. The negative effect of single parenthood remains significant in Japan, even after parent‐child communication is controlled. Interpreting the weak effect of single parenthood in the Asian countries, I consider extended family systems and the relatively high proportion of widowhood among causes of single parenthood.
The modulation of metal bio‐availability as a therapeutic strategy for the treatment of Alzheimer's disease
Authors: Crouch Peter J. , White Anthony R. , Bush Ashley I.
Published: July 2007

The postmortem Alzheimer's disease brain is characterized histochemically by the presence of extracellular amyloid plaques and neurofibrillary tangles. Also consistent with the disease is evidence for chronic oxidative damage within the brain. Considerable research data indicates that these three critical aspects of Alzheimer's disease are interdependent, raising the possibility that they share some commonality with respect to the ever elusive initial factor(s) that triggers the development of Alzheimer's disease. Here, we discuss reports that show a loss of metal homeostasis is also an important event in Alzheimer's disease, and we identify how metal dyshomeostasis may contribute to development of the amyloid‐β, tau and oxidative stress biology of Alzheimer's disease. We propose that therapeutic agents designed to modulate metal bio‐availability have the potential to ameliorate several of the dysfunctional events characteristic of Alzheimer's disease. Metal‐based therapeutics have already provided promising results for the treatment of Alzheimer's disease, and new generations of pharmaceuticals are being developed. In this review, we focus on copper dyshomeostasis in Alzheimer's disease, but we also discuss zinc and iron.
Brazilian health regions and scales: A geographical perspective
Authors: Guimarães Raul Borges
Published: July 2007

Abstract:  This paper offers a geographical perspective on the way in which health regions have been defined and established in São Paulo as part of overall Brazilian health policy. To accomplish this, I first situate the Brazilian case in the international debate over the regionalization of health services. Second, I examine health regionalization in the case of São Paulo and show how the process is dynamic and complex, involving geographical scales that go well beyond the administrative boundaries of Brazilian municipalities.
Imaging Mitochondria in Living Corneal Endothelial Cells Using Autofluorescence Microscopy
Authors: Ramey Nicholas A. , Park Choul Yong , Gehlbach Peter L. , Chuck Roy S.
Published: July 2007

We report noninvasive autofluorescence mitochondrial imaging in cultured human corneal endothelial cells (HCECs). HCECs harvested from eye bank corneas were cultured in thin glass‐bottom plates. Mitochondria were imaged with an autofluorescence microscope using a DAPI filter set (excitation: G365, emission: band pass 445/50) and then, after fixation with 4% paraformaldehyde, cells were stained with MitoTracker™ Green FM (MTG). Both images were aligned using a linear conformal algorithm for image mapping based on manually selected corresponding feature points, and then mathematically compared using two‐dimensional spatial image correlation coefficients. Autofluorescence imaging provided highly resolved mitochondrial signals from living HCECs, comparable to those taken with MTG. Both techniques yielded very similar images at high magnification and high resolution, demonstrating the tubular morphology and cytoplasmic distribution that are characteristic of mitochondria. Image registration using a linear conformal mapping technique and cross‐correlations showed high correlation of overlapping autofluorescence and MTG images. This study validates the novel use of autofluorescence vital imaging as a noninvasive, inexpensive and functional alternative to the mitochondria‐specific dyes in cultured HCEC. This noninvasive mitochondrial imaging technique can be useful in future applications studying mitochondrial biology of ocular cells.
Photodynamic Action of Benzo[a]pyrene in K562 Cells
Authors: De Moraes Vaz Batista Filgueira Daza , Paula Salomão de Freitas Diana , Paula de Souza Votto Ana , Fillmann Gilberto , Maria Monserrat José , Alicia Geracitano Laura , Santos Trindade Gilma
Published: July 2007

Benzo[a]pyrene (BaP) is ubiquitously distributed in the environment, being considered the most phototoxic element among polycyclic aromatic hydrocarbon (PAHs). In presence of oxygen, PAHs can act as a photosensitizer by means of promoting photo‐oxidation of biological molecules (photodynamic action, PDA). Thus, the present study analyzed the photodynamic action of BaP under UVA irradiation (BaP + UVA) and its oxidative effects on K562 cells. The evaluation of BaP kinetics showed that the highest intracellular concentration occurred after 18 h of incubation. Cell viability, reactive oxygen species (ROS) generation, lipid peroxidation, DNA damage (breaks and DNA–protein cross‐link [DNAPC]) were assessed after exposure to BaP, UVA and BaP plus UVA irradiation (BaP + UVA). Cell viability was decreased just after exposure to BaP + UVA. Lipid peroxidation and DNA breaks increased after BaP + UVA exposure, while the DNAPC increased after BaP, UVA and BaP + UVA exposure, suggesting that BaP + UVA effects were a consequence of both type II (producing mainly singlet oxygen) and type I (producing others ROS) mechanisms of PDA.
Modulation of TASK‐like background potassium channels in rat arterial chemoreceptor cells by intracellular ATP and other nucleotides
Authors: Varas Rodrigo , Wyatt Christopher N. , Buckler Keith J.
Published: July 2007

The carotid body's physiological role is to sense arterial oxygen, CO2and pH. It is however, also powerfully excited by inhibitors of oxidative phosphorylation. This latter observation is the cornerstone of the mitochondrial hypothesis which proposes that oxygen is sensed through changes in energy metabolism. All of these stimuli act in a similar manner, i.e. by inhibiting a background TASK‐like potassium channel (KB) they induce membrane depolarization and thus neurosecretion. In this study we have evaluated the role of ATP in modulating KBchannels. We find that KBchannels are strongly activated by MgATP (but not ATP4−) within the physiological range (K1/2= 2.3 mm). This effect was mimicked by other Mg‐nucleotides including GTP, UTP, AMP‐PCP and ATP‐γ‐S, but not by PPior AMP, suggesting that channel activity is regulated by a Mg‐nucleotide sensor. Channel activation by MgATP was not antagonized by either 1 mmAMP or 500 μmADP. Thus MgATP is probably the principal nucleotide regulating channel activity in the intact cell. We therefore investigated the effects of metabolic inhibition upon both [Mg2+]i, as an index of MgATP depletion, and channel activity in cell‐attached patches. The extent of increase in [Mg2+]i(and thus MgATP depletion) in response to inhibition of oxidative phosphorylation were consistent with a decline in [MgATP]iplaying a prominent role in mediating inhibition of KBchannel activity, and the response of arterial chemoreceptors to metabolic compromise.
Skeletal muscle vasodilatation at the onset of exercise
Authors: Clifford Philip S.
Published: July 2007

The mechanism for exercise hyperaemia is a century old enigma. Much of the research on the topic has focused on the factors controlling skeletal muscle blood flow during steady‐state dynamic exercise. It is likely that the factors which initiate the increase in blood flow are distinct from those which sustain the elevated blood flow. There is now convincing evidence that there is rapid vasodilatation following release of muscle contraction. Metabolic, neural and acetylcholine spillover mechanisms do not appear to explain the initial dilatation. Heretofore there has been only circumstantial evidence regarding the role of potassium released by skeletal muscle fibres. Studies which interrupt potassium‐mediated dilatation are just emerging and are not conclusive. In addition, the latency of the vascular smooth muscle response to potassium makes it desirable to identify a mechanism that does not rely on diffusion of a vasoactive agent. Compression of the intramuscular arterioles during contraction could activate a mechanosensitive response by the vascular smooth muscle and/or endothelium. Recent in vitro and in vivo data support the notion that brief periods of mechanical compression elicit rapid vasodilatation. Thus, vascular compression could represent a feedforward mechanism for initiating skeletal muscle vasodilatation at the onset of exercise.
The roles of adenosine and related substances in exercise hyperaemia
Authors: Marshall Janice M.
Published: July 2007

The role of adenosine in exercise hyperaemia has been controversial. Accumulating evidence now demonstrates that adenosine is released into the venous efflux of exercising muscle and that adenosine is responsible for 20–40% of the maintained phase of the muscle vasodilatation that accompanies submaximal and maximal contractions. This adenosine is mainly generated from AMP that is released from the skeletal muscle fibres and dephosphorylated by ecto 5′nucleotidase bound to the sarcolemma. During exercise, the concentration of ecto 5′nucleotidase may be increased by translocation from the cytosol, while release of AMP and affinity of ecto 5′nucleotidase for AMP are increased by acidosis. The adenosine so formed, acts on extraluminal A2A receptors on the vascular smooth muscle. In addition, ATP is released from red blood cells into the plasma during exercise, in association with the unloading of O2 from haemoglobin, while ATP and adenosine may be released from endothelium as a consequence of local hypoxia. It is unlikely that this intraluminal ATP, or adenosine, contributes significantly to exercise hyperaemia, for muscle vasodilatation induced by intraluminal ATP or adenosine is strongly nitric oxide dependent, while vasodilatation induced by adenosine in hypoxia is mediated by A1 receptors. Neither is a recognized feature of exercise hyperaemia.
Image reconstruction via the finite Hilbert transform of the derivative of the backprojection
Authors: Zeng Gengsheng L.
Published: July 2007

An exact analytical image reconstruction method is presented for two‐dimensional imaging. The method performs backprojection, the derivative and finite Hilbert transforms. This method can be applied to many imaging geometries. The backprojection procedure is imaging‐geometry dependent, while the differentiation and the finite Hilbert transform procedures are identical for all imaging geometries. This algorithm is applicable to list‐mode data in nuclear medicine, while other filtered backprojection algorithms cannot be applied directly to the list‐mode data.
Beam hardening: Analytical considerations of the effective attenuation coefficient of x‐ray tomography
Authors: Alles J. , Mudde R. F.
Published: July 2007

Polychromatic x‐ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fluence is one‐to‐one related to the traveled distance in case of a polychromatic beam moving through a given, inhomogeneous material. On the basis of this one‐to‐one relation, it is useful to define a mean attenuation coefficient and study its decrease with depth. Our results are based on a novel parametrization of the energy dependence of the attenuation coefficient that allows for closed form evaluation of certain spectral integrals. This approach underpins the ad hoc semianalytical expressions given in the literature. An analytical model for the average attenuation coefficient is proposed that uses a simple fit of the attenuation coefficient as a function of the photon energy as input. It is shown that a simple extension of this model gives a rather good description of beam hardening for x‐rays traveling through water.
Preliminary validation of a new variable pattern for daily quality assurance of medical image display devices
Authors: Jacobs Jurgen , Rogge Frank , Kotre John , Marchal Guy , Bosmans Hilde
Published: July 2007

This paper reports on a comparative study between the well‐established test patterns for daily quality assurance (QA) of monitors of the American Association of Medical Physicists, Task Group 18 (AAPMtg18) and the Deutsches Institut für Normung e.V (DIN), and a newly proposed variable test pattern. A characteristic of the test patterns currently used for the QA of monitors is their static nature: The same test pattern is always used. This enables a learning effect that may bias the results over time. To address this problem we have developed a variable pattern for the quality assurance of monitors (MoniQA) that allows an evaluation of contrast visibility, geometric distortion, resolution, global image quality including uniformity, and artifacts. The test pattern includes randomly generated elements intended to prevent the observer from learning the test. Examples are random characters that have to be discriminated from the background to evaluate the threshold luminance difference and variable positions of different features in the test pattern. The newly proposed test patterns were generated and visualized on different viewing stations with a software tool developed in JAVA. In this study, we validated these patterns against the well‐known AAPMtg18 and DIN test patterns on 22 monitors. The results showed that the MoniQA test can indicate the same monitor problems as the other well‐known patterns and is significantly quicker to evaluate than the AAPMtg18 test patterns. The MoniQA pattern is a promising alternative for daily quality control of medical viewing stations.
The future of PACS
Authors: Nagy Paul G.
Published: July 2007

How will the future of picture archiving and communication systems (PACS) look, and how will this future affect the practice of radiology? We are currently experiencing disruptive innovations that will force an architectural redesign, making the majority of today's commercial PACS obsolete as the field matures and expands to include imaging throughout the medical enterprise. The common architecture used for PACS cannot handle the massive amounts of data being generated by even current versions of computed tomography and magnetic resonance scanners. If a PACS cannot handle today's technology, what will happen as the field expands to encompass pathology imaging, cone‐beam reconstruction, and multispectral imaging? The ability of these new technologies to enhance research and clinical care will be impaired if PACS architectures are not prepared to support them. In attempting a structured approach to predictions about the future of PACS, we offer projections about the technologies underlying PACS as well as the evolution of standards development and the changing needs of a broad range of medical imaging. Simplified models of the history of the PACS industry are mined for the assumptions they provide about future innovations and trends. The physicist frequently participates in or directs technical assessments for medical equipment, and many physicists have extended these activities to include imaging informatics. It is hoped that by applying these speculative but experienced‐based predictions, the interested medical physicist will be better able to take the lead in setting information technology strategies that will help facilities not only prepare for the future but continue to enjoy the benefits of technological innovations without disruptive, expensive, and unexpected changes in architecture. A good PACS strategy can help accelerate the time required for innovations to go from the drawing board to clinical implementation.
A technique of quantitatively monitoring both respiratory and nonrespiratory motion in patients using external body markers
Authors: Jin Jian‐Yue , Ajlouni Munther , Ryu Samuel , Chen Qing , Li Shidong , Movsas Benjamin
Published: July 2007

The purpose of this study was to develop a technique that could quantitatively monitor the nonrespiratory motion of a patient during stereotactic body radiotherapy (SBRT). Multiple infrared external markers were placed on the patient's chest and abdominal surface to obtain patient motion signals. These motion signals contained both respiratory and nonrespiratory motion information. The respiratory motion usually has much larger amplitude on the abdominal surface than on the chest surface. Assuming that the nonrespiratory motion is a rigid body translation, we have developed a computer algorithm to derive both the respiratory and nonrespiratory motion signals instantly from two sets of motion signals. In first‐order approximation, the respiratory motion was represented by the motion signal on the abdominal surface, and the nonrespiratory motion was represented by the motion signal on the chest surface subtracting its respiratory component. The algorithm was retrospectively tested on 24 patients whose motion signals were recorded during a gated‐CT simulation procedure. The result showed that the respiratory noise in the nonrespiratory motion signal was reduced to less than for almost all patients, demonstrating that the technique was able to detect nonrespiratory motion with a sensitivity of about . It also showed that 50% of the patients had , and 2 patients had slow drift during the 15– simulation procedure, suggesting that nonrespiratory motion could exist during prolonged treatment. This technique can potentially be used to control the nonrespiratory motion during SBRT. However, further validation is required for its clinical use.
Quantitative evaluation of a beam‐matching procedure using one‐dimensional gamma analysis
Authors: Hrbacek Jan , Depuydt Tom , Nulens An , Swinnen Ans , Van den Heuvel Frank
Published: July 2007

This article provides a quantitative evaluation of Varian Medical Systems’ beam matching procedure. A one‐dimensional analysis is employed to investigate the level of agreement of matched beams. A customized concept of one‐dimensional evaluation was designed. Our algorithm first performs a “local” fit of the reference and the evaluated datasets. For a particular point on the fitted evaluated curve, the is derived as the shortest distance between the point and the fitted reference curve. This approach removes variations of the obtained value related to the discrete character and noise in the original datasets. Criteria of distance‐to‐agreement and 1% dose difference were used to evaluate the level of agreement of according profiles. Relative point and profile measurements were performed for all photon and electron beams of two Varian Clinacs 2100C/D. Matched beams show a good level of agreement. 70% of profiles completely pass the chosen criteria. The analysis of remaining 30% of the profiles demonstrates that measurement error becomes a limiting factor in achieving a better score. The highest obtained value was 1.70. The quality of beam matching allowed us to treat according beams of both treatment units as “identical” and to use the reference beam data for the new unit. Nevertheless, the vendor's acceptance criteria of beam matching are much more benevolent. It might happen that the acceptance criteria are met, however, resulting quality of beam matching does not allow full interchangeability of beams.
Experimental verification of beam quality in high‐contrast imaging with orthogonal bremsstrahlung photon beamsa)
Authors: Sarfehnia Arman , Jabbari Keyvan , Seuntjens Jan , Podgorsak Ervin B.
Published: July 2007

Since taken with megavoltage, forward‐directed bremsstrahlung beams, the image quality of current portal images is inferior to that of diagnostic quality images produced by kilovoltage beams. In this paper, the beam quality of orthogonal bremsstrahlung beams defined as the 90° component of the bremsstrahlung distribution produced from megavoltage electron pencil beams striking various targets is presented, and the suitability of their use for improved radiotherapy imaging is evaluated. A electron beam emerging through the research port of a Varian Clinac‐18 linac was made to strike targets of carbon, aluminum, and copper. PDD and attenuation measurements of both the forward and orthogonal beams were carried out, and the results were also used to estimate the effective and mean energy of the beams. The mean energy of a spectrum produced by a carbon target dropped by 83% from in the forward direction to in the orthogonal direction, while for an aluminum target it dropped by 77% to , and for a copper target by 65% to . An in‐depth Monte Carlo study of photon yield and electron contamination was also performed. Photon yield and effective energy are lower for orthogonal beams than for forward beams, and the differences are more pronounced for targets of lower atomic number. Using their relatively low effective energy, orthogonal bremsstrahlung beams produced by megavoltage electrons striking low atomic number targets yield images with a higher contrast in comparison with forward bremsstrahlung beams.
Prostate brachytherapy seed reconstruction using an adaptive grouping technique
Authors: Su Yi , Davis Brian J. , Furutani Keith M. , Herman Michael G. , Robb Richard A.
Published: July 2007

Fluoroscopy‐based three‐dimensional seed localization as a component of intraoperative dosimetry for prostate brachytherapy is an active area of research. A novel adaptive‐grouping‐based reconstruction approach is developed. This approach can recover overlapped seeds that are not detected from the fluoroscopic images. Two versions of the adaptive‐grouping‐based reconstruction approach are implemented and compared to an epipolar geometry‐based seed reconstruction technique. Simulations based on nine patient datasets are used to validate the algorithms. A total of 2259 reconstructions is performed in which different types of error such as random noise in seed image locations and ambiguities in projection geometry are incorporated. Among those reconstructions, nine of the cases with overlapping seeds and the different types of error are performed. It is demonstrated that the adaptive‐grouping‐based reconstruction method is more accurate than the epipolar geometry method and allows faster reconstruction. At a random noise level of , the mean distance error in reconstructed seed locations is approximately for one of the relevant cases examined in detail. The best adaptive‐grouping‐based approach successfully recovered overlapped seeds in the majority of simulated cases (89%), with the remainder of cases generating one false positive seed. Phantom validation is also performed, and overlapped seeds are successfully recovered with all 92 seeds correctly localized and reconstructed. The mean distance error between segmented seed images and projected seeds is in the phantom study.
A temporal interpolation approach for dynamic reconstruction in perfusion CT
Authors: Montes Pau , Lauritsch Günter
Published: July 2007

This article presents a dynamic CT reconstruction algorithm for objects with time dependent attenuation coefficient. Projection data acquired over several rotations are interpreted as samples of a continuous signal. Based on this idea, a temporal interpolation approach is proposed which provides the maximum temporal resolution for a given rotational speed of the CT scanner. Interpolation is performed using polynomial splines. The algorithm can be adapted to slow signals, reducing the amount of data acquired and the computational cost. A theoretical analysis of the approximations made by the algorithm is provided. In simulation studies, the temporal interpolation approach is compared with three other dynamic reconstruction algorithms based on linear regression, linear interpolation, and generalized Parker weighting. The presented algorithm exhibits the highest temporal resolution for a given sampling interval. Hence, our approach needs less input data to achieve a certain quality in the reconstruction than the other algorithms discussed or, equivalently, less x‐ray exposure and computational complexity. The proposed algorithm additionally allows the possibility of using slow rotating scanners for perfusion imaging purposes.
Angular on‐line tube current modulation in multidetector CT examinations of children and adults: The influence of different scanning parameters on dose reduction
Authors: Papadakis Antonios E. , Perisinakis Kostas , Damilakis John
Published: July 2007

The purpose of this study was to assess the potential of angular on‐line tube current modulation on dose reduction in pediatric and adult patients undergoing multidetector computed tomography (MDCT) examinations. Five physical anthropomorphic phantoms that simulate the average individual as neonate, ‐old, ‐old, ‐old, and adult were employed in the current study. Phantoms were scanned with the use of on‐line tube current modulation (TCM). Percent dose reduction (%DR) factors achieved by applying TCM, were determined for standard protocols used for head and neck, shoulder, thorax, thorax and abdomen, abdomen, abdomen and pelvis, pelvis, and whole body examinations. A preliminary study on the application of TCM in MDCT examinations of adult patients was performed to validate the results obtained in anthropomorphic phantoms. Dose reduction was estimated as the percentage difference of the modulated milliamperes for each scan and the preset milliamperes prescribed by the scan protocol. The dose reduction in children was found to be much lower than the corresponding reduction achieved for adults. For helical scans the %DR factors, ranged between 1.6% and 7.4% for the neonate, 2.9% and 8.7% for the old, 2% and 6% for the ‐old, 5% and 10.9% for the ‐old, and 10.4% and 20.7% for the adult individual. For sequential scans the corresponding %DR factors ranged between 1.3% and 6.7%, 4.5% and 11%, 4.2% and 6.6%, 6.4% and 12.3%, and 8.9% and 23.3%, respectively. Broader beam collimations are associated with decreased %DR factors, when other scanning parameters are held constant. TCM did not impair image noise. In adult patients, the %DR values were found to be in good agreement with the corresponding results obtained in the anthropomorphic adult phantom. In conclusion, on‐line TCM may be considered as a valuable tool for reducing dose in routine CT examinations of pediatric and adult patients. However, the dose reduction achieved with TCM in neonates and young children was found to be lower than that obtained for adults. Therefore, on‐line TCM should work as an additional means to reduce dose and should not replace other conventional means of reducing dose, especially in neonates and young children.
Comparison of maximum intensity projection and digitally reconstructed radiographic projection for carotid artery stenosis measurement
Authors: Hyde Derek E. , Habets Damiaan F. , Fox Allan J. , Gulka Irene , Kalapos Paul , Lee Don H. , Pelz David M. , Holdsworth David W.
Published: July 2007

Digital subtraction angiography is being supplanted by three‐dimensional imaging techniques in many clinical applications, leading to extensive use of maximum intensity projection (MIP) images to depict volumetric vascular data. The MIP algorithm produces intensity profiles that are different than conventional angiograms, and can also increase the vessel‐to‐tissue contrast‐to‐noise ratio. We evaluated the effect of the MIP algorithm in a clinical application where quantitative vessel measurement is important: internal carotid artery stenosis grading. Three‐dimensional computed rotational angiography (CRA) was performed on 26 consecutive symptomatic patients to verify an internal carotid artery stenosis originally found using duplex ultrasound. These volumes of data were visualized using two different postprocessing projection techniques: MIP and digitally reconstructed radiographic (DRR) projection. A DRR is a radiographic image simulating a conventional digitally subtracted angiogram, but it is derived computationally from the same CRA dataset as the MIP. By visualizing a single volume with two different projection techniques, the postprocessing effect of the MIP algorithm is isolated. Vessel measurements were made, according to the NASCET guidelines, and percentage stenosis grades were calculated. The paired t‐test was used to determine if the measurement difference between the two techniques was statistically significant. The CRA technique provided an isotropic voxel spacing of . The MIPs and DRRs had a mean signal‐difference‐to‐noise‐ratio of 30:1 and 26:1, respectively. Vessel measurements from MIPs were, on average, larger than those from DRRs . The NASCET‐type stenosis grades tended to be underestimated on average by 2.4% with the MIP algorithm, although this was not statistically significant . The mean interobserver variability (standard deviation) of both the MIP and DRR images was . It was concluded that the MIP algorithm slightly increased the apparent dimensions of the arteries, when applied to these intra‐arterial CRA images. This subpixel increase was smaller than both the voxel size and interobserver variability, and was therefore not clinically relevant.
Recreational boating traffic: A chronic source of anthropogenic noise in the Wilmington, North Carolina Intracoastal Waterway
Authors: Haviland-Howell Genevieve , Frankel Adam S. , Powell Christopher M. , Bocconcelli Alessandro , Herman Russell L. , Sayigh Laela S.
Published: July 2007

The majority of attention on the impact of anthropogenic noise on marine mammals has focused on low-frequency episodic activities. Persistent sources of mid-frequency noise pollution are less well studied. To address this data gap, the contribution of 25 physical, biological and anthropogenic factors to the ambient noise levels in the Wilmington, North Carolina Intracoastal Waterway were analyzed using a principal components analysis and least squares regression. The total number of recreational vessels passing through the waterway per hour is the factor that had the single greatest influence on environmental noise levels. During times of high boat traffic, anthropogenic noise is continuous rather than episodic, and occurs at frequencies that are biologically relevant to bottlenose dolphins. As a daily part of resident bottlenose dolphins’ acoustic environment, recreational boating traffic may represent a chronic source of acoustic harassment.
Detection performances of experienced human operators compared to a likelihood ratio based detector
Authors: Urazghildiiev Ildar R. , Clark Christopher W.
Published: July 2007

This paper compares the detection performances of experienced human operators and an automatic detector that is based on the generalized likelihood ratio test (GLRT). Test data consist of polynomial phase signals and additive white Gaussian noise with signal-to-noise-ratios of 18, 20, 24, and 24dB. Test results demonstrate that, for a given human operator false alarm probability, the GLRT-based detector provided a higher probability of detecting signals than human operators.
Using a signal cancellation technique to assess adaptive directivity of hearing aids
Authors: Wu Yu-Hsiang , Bentler Ruth A.
Published: July 2007

The directivity of an adaptive directional microphone hearing aid (DMHA) cannot be assessed by the method that calls for presenting a “probe” signal from a single loudspeaker to the DMHA that moves to different angles. This method is invalid because the probe signal itself changes the polar pattern. This paper proposes a method for assessing the adaptive DMHA using a “jammer” signal, presented from a second loudspeaker rotating with the DMHA, that simulates a noise source and freezes the polar pattern. Measurement at each angle is obtained by two sequential recordings from the DMHA, one using an input of a probe and a jammer, and the other with an input of the same probe and a phase-inverted jammer. After canceling out the jammer, the remaining response to the probe signal can be used to assess the directivity. In this paper, the new method is evaluated by comparing responses from five adaptive DMHAs to different jammer intensities and locations. This method was shown to be an accurate and reliable way to assess the directivity of the adaptive DMHA in a high-intensity-jammer condition.
Simultaneously measured behavioral and electrophysiological hearing thresholds in a bottlenose dolphin (Tursiops truncatus)
Authors: Schlundt Carolyn E. , Dear Randall L. , Green Linda , Houser Dorian S. , Finneran James J.
Published: July 2007

Dolphin auditory thresholds obtained via evoked potential audiometry may deviate from behavioral estimates by 20dB or more. Differences in the sound source, stimulus presentation method, wave form, and duration may partially explain these discrepancies. To determine the agreement between behavioral and auditory evoked potential (AEP) threshold estimates when these parameters are held constant, behavioral and AEP hearing tests were simultaneously conducted in a bottlenose dolphin. Measurements were made in-air, using sinusoidal amplitude-modulated tones continuously projected via a transducer coupled to the pan region of the dolphin’s lower jaw. Tone trials were presented using the method of constant stimuli. Behavioral thresholds were estimated using a 50% correct detection. AEP thresholds were based on the envelope following response and 50% correct detection. Differences between AEP and behavioral thresholds were within ±5dB, except at 10kHz (12dB), 20kHz (8dB), 30kHz (7dB), and 150kHz (24dB). In general, behavioral thresholds were slightly lower, though this trend was not significant. The results demonstrate that when the test environment, sound source, stimulus wave form, duration, presentation method, and analysis are consistent, the magnitude of the differences between AEP and behavioral thresholds is substantially reduced.
Testing theories of vowel inherent spectral change
Authors: Morrison Geoffrey Stewart , Nearey Terrance M.
Published: July 2007

Three competing accounts of vowel inherent spectral change in English all agree on the importance of initial formant frequencies; however, they disagree about the nature of the perceptually relevant aspects of formant change. The onset+offset hypothesis claims that the final formant values themselves matter. The onset+slope hypothesis claims that only the rate of change counts. The onset+direction hypothesis claims that only the general direction of change in formant frequencies is important. A synthetic-vowel perception experiment was designed to differentiate among the three. Results provide support for the superiority of the onset+offset hypothesis.
Age-related differences in discrimination of an interval separating onsets of successive tone bursts as a function of interval duration
Authors: Fitzgibbons Peter J. , Gordon-Salant Sandra , Barrett Jessica
Published: July 2007

The study measured listener sensitivity to increments in the inter-onset interval (IOI) separating pairs of successive 20-ms 4000-Hz tone pulses. A silent interval between the tone pulses was adjusted across conditions to create reference tonal IOI values of 25–600ms. For each condition, a duration DL for increments of the tonal IOI was measured in listeners comprised of young normal-hearing adults and two groups of older adults with and without high-frequency hearing loss. Discrimination performance of all listeners was poorest for the shorter reference IOIs, and improved to stable levels for longer reference intervals exceeding about 200ms. Temporal sensitivity of the young listeners was significantly better than that of the elderly listeners in each condition, with the largest age-related differences observed for the shortest reference interval. Age-related differences were also observed for duration DLs measured using single 4000-Hz tone bursts set to three reference durations in the range 50–200ms. The tone DLs of all listeners were smaller than the corresponding tone-pair IOI DLs, particularly for the shorter reference stimulus durations. There were no significant performance differences observed between the older listeners with and without hearing loss for either discrimination task.
Observing individual fish behavior in fish aggregations: Tracking in dense fish aggregations using a split-beam echosounder
Authors: Handegard Nils Olav
Published: July 2007

Acoustic instruments are important tools for observing the behavior of aquatic organisms. This paper presents a simple but efficient method for improving the tracking of closely spaced targets using a split-beam echosounder. The traditional method has been a stepwise approach from the detection of echoes, rejection of apparently multiple targets and then tracking the remainder. This is inefficient because the split-beam angles are not included in the initial detection; rather they are only used in the rejection criteria before the subsequent tracking. A simple track-before-detection method is presented, where the phase angles, echo intensities, ranges, and times are used simultaneously, resulting in better detection and tracking of the individual fish. Two test data sets were analyzed to determine the effectiveness of this method at discriminating individual tracks from within dense fish aggregations. The first data set was collected by lowering a split-beam transducer into a herring layer. The second data set, also collected with a split-beam transducer, was from a caged aggregation of feeding herring larvae. Results indicate the potential of target tracking, using a split-beam echosounder, as a tool for understanding interindividual behavior.
Experimental characterization of onset of acoustic instability in a nonpremixed half-dump combustor
Authors: Chakravarthy Satyanarayanan R. , Shreenivasan Obla J. , Boehm Benjamin , Dreizler Andreas , Janicka Johannes
Published: July 2007

This paper reports work on a nonpremixed half-dump combustor, in which methane is injected at the backward-facing step, and mixes and burns with the air flowing past the step in the unsteady recirculation zone. The flow and geometric parameters are widely varied, to gradually change from conditions of low-amplitude noise to excitation of high-amplitude discrete tones. The purpose of the work is to focus on the transition from the former condition to the latter, and to mark the onset of instability. Dimensionless groups such as the Helmholtz and Strouhal numbers are formed based on the observed dominant frequencies, whose variation with the air flow Reynolds number is used to identify the oscillations as those due to the natural acoustic modes or the vortex shedding process. High-speed chemiluminescence imaging reveals shedding of vortical structures in the flame zone. With variation in the conditions, flow-acoustic lock-on and transition from one vortex shedding mode to another is marked by nonlinearity in the corresponding amplitude variations. Such conditions are identified as the onset of instability in terms of the ratio of the flow time scale to the acoustic time scale and mapped against the operating fuel-air equivalence ratio of the combustor.
The time-domain signature of negative acoustic group velocity in microsphere suspensions
Authors: Mobley Joel
Published: July 2007

In the wake of recent reports of superluminal acoustic group velocities in sonic and ultrasonic regions of the acoustic spectrum, this paper describes the time-domain manifestation of such group velocities through simulations of the linear propagation of ultrasonic wave packets in a suspension of elastic microspheres. Conditions under which arbitrarily large and negative group velocities can be observed as the speed of a peak in the envelope of an acoustic pulse are described. Propagation simulations demonstrate the physical signature of negative group velocities, as well as the causal compliance of the superluminal acoustic pulses examined in this work.
Natural Selection Favors a Newly Derived
timeless
Allele in
Drosophila melanogaster
Authors: Tauber Eran , Zordan Mauro , Sandrelli Federica , Pegoraro Mirko , Osterwalder Nicolò , Breda Carlo , Daga Andrea , Selmin Alessandro , Monger Karen , Benna Clara , Rosato Ezio , Kyriacou Charalambos P. , Costa Rodolfo
Published: July 2007

Circadian and other natural clock-like endogenous rhythms may have evolved to anticipate regular temporal changes in the environment. We report that a mutation in the circadian clock gene
timeless
in
Drosophila melanogaster
has arisen and spread by natural selection relatively recently in Europe. We found that, when introduced into different genetic backgrounds, natural and artificial alleles of the
timeless
gene affect the incidence of diapause in response to changes in light and temperature. The natural mutant allele alters an important life history trait that may enhance the fly's adaptation to seasonal conditions.
Are Women Really More Talkative Than Men?
Authors: Mehl Matthias R. , Vazire Simine , Ramírez-Esparza Nairán , Slatcher Richard B. , Pennebaker James W.
Published: July 2007

Women are generally assumed to be more talkative than men. Data were analyzed from 396 participants who wore a voice recorder that sampled ambient sounds for several days. Participants' daily word use was extrapolated from the number of recorded words. Women and men both spoke about 16,000 words per day.