bluuebunny/crossref_metadata_2025 huggingface dataset:
An Examination of Rater Drift Within a Generalizability Theory Framework
Authors: Harik Polina , Clauser Brian E. , Grabovsky Irina , Nungester Ronald J. , Swanson Dave , Nandakumar Ratna
Published: February 2009

The present study examined the long‐term usefulness of estimated parameters used to adjust the scores from a performance assessment to account for differences in rater stringency. Ratings from four components of the USMLE® Step 2 Clinical Skills Examination data were analyzed. A generalizability‐theory framework was used to examine the extent to which rater‐related sources of error could be eliminated through statistical adjustment. Particular attention was given to the stability of these estimated parameters over time. The results suggest that rater stringency estimates obtained at a point in time and then used to adjust ratings over a period of months may substantially decrease in usefulness. In some cases, over several months, the use of these adjustments may become counterproductive. Additionally, it is hypothesized that the rate of deterioration in the usefulness of estimated parameters may be a function of the characteristics of the scale.
Self‐Organized Permeability in Carbonate Aquifers
Authors: Worthington S.R.H. , Ford D.C.
Published: February 2009

Advances over the past 40 years have resulted in a clear understanding of how dissolution processes in carbonate rocks enhance aquifer permeability. Laboratory experiments on dissolution rates of calcite and dolomite have established that there is a precipitous drop in dissolution rates as chemical equilibrium is approached. These results have been incorporated into numerical models, simulating the effects of dissolution over time and showing that it occurs along the entire length of pathways through carbonate aquifers. The pathways become enlarged and integrated over time, forming self‐organized networks of channels that typically have apertures in the millimeter to centimeter range. The networks discharge at point‐located springs. Recharge type is an important factor in determining channel size and distribution, resulting in a range of aquifer types, and this is well demonstrated by examples from England. Most carbonate aquifers have a large number of small channels, but in some cases large channels (i.e., enterable caves) can also develop. Rapid velocities found in ground water tracer tests, the high incidence of large‐magnitude springs, and frequent microbial contamination of wells all support the model of self‐organized channel development. A large majority of carbonate aquifers have such channel networks, where ground water velocities often exceed 100 m/d.
Effectiveness of check dams in the control of general transitory bed scouring in semiarid catchment areas (South‐East Spain)
Authors: Conesa‐García C. , García‐Lorenzo R.
Published: February 2009

The semiarid areas of the Spanish Mediterranean region are environments that are severely threatened by desertification. Hydrological‐forestry restoration is a very useful tool to fight these processes in programmes and projects of basin management. Check dams particularly can control bed erosion in ephemeral channels, among other things. The main aim of this study, then, is to evaluate how much check dams influence the degree of transitory general scouring in dry alluvial channels that function only sporadically and as torrents. Two areas were chosen: the Cárcavo and Torrecilla catchments (River Segura basin), both drained by ephemeral gullies and both having undergone hydrological correction projects during the 1970s. Equations based on grain bed movement commencement criteria were applied for floods of different water depths, bearing in mind bed texture changes and slope adjustment brought about by dam construction. The results are contrasted with the critical velocity values, which in turn depend on the flow depth and the cross‐section area before flooding. Finally, a comparison between real and predicted scouring is established for the cases analysed, including bankfull flow. Especially, the usefulness of Neill's method has been tested in relation to net erosion values measured in the field with successful results.
In Defense of Bioethics
Authors: Baker Robert
Published: February 2009

Reading Scofield’s scathing indictment of my field, bioethics, reminded me of how it felt, as an American liberal committed to the cause of racial justice, to read Soviet diatribes against American racism published during the Cold War. I shared with the authors a deep commitment to rectify the injustices they protested. Yet, like Scofield, they proffered accounts of events so radically selective and decontextualized that their version of history seemed more akin to fiction than to fact.
Teaching Health Law
Authors: Leonard Elizabeth Weeks
Published: February 2009

In long Midwestern winters, two things are certain: snow and basketball. But two things that you cannot count on are snow day school closures and a home-team collegiate basketball championship. In Kansas last winter, we had both. Winter precipitation was much above average, resulting in a rare invocation of the University's inclement weather policy to cancel classes in early February. And the Kansas Jayhawks basketball team brought home the National Collegiate Athletic Association championship trophy for the first time in two decades. The Chancellor commemorated the achievement with a campuswide celebration, including all-day class cancellation. This is all well and good. I am all for respecting Mother Nature's forces and celebrating remarkable athletic accomplishments.

But the combination of events does leave law professors nearing the end of the semester in a bit of a quandary. How to make up the cancelled classes to ensure compliance with American Bar Association accreditation instructional hours requirements? How to cover the missed course content? How to find mutually agreeable make-up class times and locations with a group of busy, upper-level law students?
Recent Developments in Health Law
Authors: Ang Ching Ping , Wolpin Joseph , Baron Elisha
Published: February 2009

As of July 1, 2008, females aged 11-26 years seeking status as permanent residents in the United States must produce documentation that they have received the human papillomavirus (HPV) vaccine before the U.S. Citizenship and Immigration Services will approve their status adjustment. Immigration rights activists and public health officials have objected to this new requirement on the grounds that it is unnecessary and imposes unreasonable barriers to lawful immigration due to its expense. The Supreme Court has generally upheld mandatory vaccination requirements for citizens and non-citizens and has tolerated federal immigration regulations that would be unconstitutional if applied to citizens. However, the HPV vaccination requirement may be arbitrary, unnecessary, and discriminatory as applied to green card applicants who pose no greater threat to public health than citizens who are not subject to the same requirements. Furthermore, the requirement may also impose unreasonable restraints on aliens individual liberties as well as real barriers to immigration.
Effect of Extrusion Cooking on Functional Properties and in vitro Starch Digestibility of Barley‐Based Extrudates from Fruit and Vegetable By‐Products
Authors: Altan A. , McCarthy K.L. , Maskan M.
Published: February 2009

ABSTRACT:  Barley flour and barley flour–pomace (tomato, grape) blends were extruded through a co‐rotating twin‐screw extruder. The aim of the present study was to investigate the effects of die temperature, screw speed, and pomace level on water absorption index (WAI), water solubility index (WSI), degree of starch gelatinization, and in vitro starch digestibility using a response surface methodology. The selected extrudate samples were examined further using differential scanning calorimetry (DSC) and polarized light microscopy, respectively. The WAI of barley–pomace extrudates was affected by increasing pomace level. Temperature had significant effect on all types of extrudate but screw speed had significant linear effect only on barley and barley–grape pomace extrudates on degree of starch gelatinization. Although no gelatinization peak was detected, an endotherm was observed on all selected extrudates. In general, extrusion cooking significantly increased in vitro starch digestibility of extrudates. However, increasing level of both tomato and grape pomace led to reduction in starch digestibility.
Retinal Conformation and Dynamics in Activation of Rhodopsin Illuminated by Solid‐state 2H NMR Spectroscopy†
Authors: Brown Michael F. , Martínez‐Mayorga Karina , Nakanishi Koji , Salgado Gilmar F. J. , Struts Andrey V.
Published: February 2009

Solid‐state NMR spectroscopy gives a powerful avenue for investigating G protein‐coupled receptors and other integral membrane proteins in a native‐like environment. This article reviews the use of solid‐state 2H NMR to study the retinal cofactor of rhodopsin in the dark state as well as the meta I and meta II photointermediates. Site‐specific 2H NMR labels have been introduced into three regions (methyl groups) of retinal that are crucially important for the photochemical function of rhodopsin. Despite its phenomenal stability 2H NMR spectroscopy indicates retinal undergoes rapid fluctuations within the protein binding cavity. The spectral lineshapes reveal the methyl groups spin rapidly about their three‐fold (C3) axes with an order parameter for the off‐axial motion of For the dark state, the 2H NMR structure of 11‐cis‐retinal manifests torsional twisting of both the polyene chain and the β‐ionone ring due to steric interactions of the ligand and the protein. Retinal is accommodated within the rhodopsin binding pocket with a negative pretwist about the C11=C12 double bond. Conformational distortion explains its rapid photochemistry and reveals the trajectory of the 11‐cis to trans isomerization. In addition, 2H NMR has been applied to study the retinylidene dynamics in the dark and light‐activated states. Upon isomerization there are drastic changes in the mobility of all three methyl groups. The relaxation data support an activation mechanism whereby the β‐ionone ring of retinal stays in nearly the same environment, without a large displacement of the ligand. Interactions of the β‐ionone ring and the retinylidene Schiff base with the protein transmit the force of the retinal isomerization. Solid‐state 2H NMR thus provides information about the flow of energy that triggers changes in hydrogen‐bonding networks and helix movements in the activation mechanism of the photoreceptor.
Structural Coupling of 11‐cis‐7‐Methyl‐retinal and Amino Acids at the Ligand Binding Pocket of Rhodopsin†
Authors: Aguilà Mònica , Toledo Darwin , Morillo Margarita , Dominguez Marta , Vaz Belén , Alvarez Rosana , De Lera Angel R. , Garriga Pere
Published: February 2009

It was previously shown that opsin can be regenerated with the newly synthesized 11‐cis‐7‐methyl‐retinal forming an artificial visual pigment. We now extend this study to include mutants at positions close to the retinal to further dissect the interactions of native and artificial chromophores with opsin. Several mutants at M207, W265 and Y268 have been obtained and regenerated with 11‐cis‐retinal and the 7‐methyl analog. M207 is the site of the point mutation M207R associated with the retinal degenerative disease retinitis pigmentosa. All the studied mutants regenerated with 11‐cis‐retinal except for M207C which proved to be completely misfolded. The naturally occurring M207R mutant formed a pigment with an unprotonated Schiff base linkage, altered photobleaching and low MetarhodopsinII stability. Mutants regenerated with the 7‐methyl analog showed altered photobleaching reflecting a structural perturbation in the vicinity of M207. The newly obtained mutants at M207 also showed reduced levels of transducin activation with M207R showing essentially no transducin activation. Our results highlight the tight coupling of the vicinity of C7 of retinal and M207 and support the involvement of this amino acid residue in the conformational changes associated with rhodopsin photoactivation.
Mineralogical Characteristics and Cationic Exchange Properties of a Zeolite Mineral from Romana, NW Sardinia, Italy
Authors: Fercia Maria L. , Lonis Roberto , Peretti Roberto , Sau Antonio , Serci Antonello , Zucca Antonio
Published: February 2009

An investigation was conducted into the Tertiary ignimbrite formations in the Romana area in NW Sardinia. Scanning electron microscopy–energy‐dispersive spectrometry indicated the presence of clinoptilolite and subordinate smectite, quartz, mordenite and calcite. Laboratory analyses of representative samples collected from the deposit indicated a cation exchange capacity ranging from 85 to 135 mEq per 100 g. Ion exchange experiments conducted in flasks containing different initial cation concentrations and in columns supplied with solution having constant cation concentration, showed different selectivity towards the cations examined, in the order: NH4+> Pb2+> Cd2+> Cu2+> Zn2+> Mn2+> Ni2+. Compared to the untreated material, under the experimental conditions used and considering the eluate, and the Italian regulatory limits for discharge into surface waters, the zeolite treated with a 1‐N NaCl solution yielded a 1.3–5‐fold increase in the volume of treated water, depending on the cation examined. The experimental results obtained show that the cationic exchange properties of the zeolite rock from the Romana deposit are comparable with the average quality of zeolites currently imported into Italy from non‐European countries.
Identity and dynamics of putative N2‐fixing picoplankton in the Baltic Sea proper suggest complex patterns of regulation
Authors: Farnelid Hanna , Öberg Tomas , Riemann Lasse
Published: February 2009

Heterocystous filamentous cyanobacteria are regarded as the main N2‐fixing organisms (diazotrophs) in the Baltic Sea. However, some studies indicate that picoplankton may also be important. The aim of this study was to examine the composition of putative diazotrophs in the picoplankton (< 3 µm) and to identify links to environmental factors. Nitrogenase (nifH) genes were amplified from community DNA by nested PCR, followed by cloning and sequencing. Clone libraries from nine environmental samples collected from the central Baltic Sea (April–October 2003, 3 m depth) and a negative control yielded a total of 433 sequences with an average clone library coverage of 92%. The sequences fell within nifH Clusters I, II and III and formed 15 distinct groups (> 96% amino acid similarity). Most of the sequences (77%) fell into nifH Cluster I (cyanobacteria and α‐, β‐ and γ‐Proteobacteria). However, only 26 sequences were related to cyanobacteria (e.g. Pseudanabaena) and among these no unicellular phylotypes were found. Sequences clustering with alternative nitrogenases (anfH) and Archaea were found in one sample while sequences related to anaerobic phylotypes were found in six samples distributed throughout the season. The identified phylogenetic groups showed covariance with several environmental factors but no strong links could be established. This suggests a variable and complex regulation of diazotrophic groups within Baltic Sea picoplankton.
Maximizing Throughput of Bucket Brigades on Discrete Work Stations
Authors: Lim Yun Fong , Yang Kum Khiong
Published: February 2009

One way to coordinate workers along an assembly line that has fewer workers than work stations is to form a bucket brigade. The throughput of a bucket brigade on discrete work stations may be compromised due to blocking even if workers are sequenced from slowest to fastest. For a given work distribution on the stations we find policies that maximize the throughput of the line. When workers have very different production rates, fully cross‐training the workers and sequencing them from slowest to fastest is almost always the best policy. This policy outperforms other policies for most work distributions except for some cases in which limiting the work zones of workers produces higher throughput. In environments where the work can be adjusted across stations, we identify conditions for a line to prevent blocking.
Influence of Power Cycling Durations on Thermal and Fatigue Reliability Characteristics of Board-Level Chip-Scale Packages
Authors: Wang Tong Hong , Lee Chang-Chi , Lai Yi-Shao , Lee Kuo-Yuan
Published: February 2009

The sequential thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, was performed in this work to investigate thermal characteristics along with fatigue reliability of a thin-profile fine-pitch ball grid array chip-scale package subjected to power cycling. The numerical model was calibrated using steady-state and power cycling experiments. Following the calibrated numerical model, different power cycling durations on the thermal characteristics and fatigue reliability of the solder joints were examined. Numerical results indicate that, compared with thermal cycling, power cycling requires many more cycles to achieve a stabilized plasticity index between test cycles. The fatigue reliability would therefore be greatly underestimated if only such an index of the first several cycles is followed in the predictions.
Integration of Ta–N Thin Film Resistors on Anodic Alumina MCM-D Substrate
Authors: Zhu Dapeng , Lin Xiaoqin , Luo Le
Published: February 2009

The aim of this work is to evaluate the changes in microstructures and electrical properties of a tantalum nitride (Ta–N) thin film integrated on an aluminum anodization multichip module deposited (MCM-D) substrate. A Ta–N resistor with a thickness of 100 nm was integrated at the bottom layer of the MCM-D substrate using rf reactive sputtering. Effects of aluminum anodization process on the Ta–N thin film resistor were studied. The results show that the oxide bulges composed of Ta2O5 and Ta–O–N are formed at the Ta–N film surface due to the effect of the upper layer of porous anodic alumina. The resistivity and the temperature coefficient of resistance of the Ta–N resistor remain unchanged. The integrated resistor is more stable owing to the protection of the oxide bulges.
Chimney Effect on Natural Convection Cooling of a Transistor Mounted on a Cooling Fin
Authors: De Mey G. , Wójcik M. , Pilarski J. , Lasota M. , Banaszczyk J. , Vermeersch B. , Napieralski A. , De Paepe M.
Published: February 2009

The thermal impedance Zth(jω) has been measured for the junction of a transistor mounted on a cooling fin. The setup was put inside a chimney in order to enhance the natural convection cooling. From the thermal impedance Zth(jω) the influence of the chimney on the reduction in thermal resistance Rth=Zth(jω=0) is clearly visible. A maximum improvement of almost 20% has been observed experimentally. Measuring the thermal impedance as a function of the angular frequency ω provides specific information about the thermal path being influenced by the chimney.
Characterization of Chemical Cure Shrinkage of Epoxy Molding Compound With Application to Warpage Analysis
Authors: Hu Guojun , Luan Jing-En , Chew Spencer
Published: February 2009

After encapsulation, thermomechanical deformation builds up within the electronic packages due to the temperature coefficient of expansion mismatch between the respective materials within the package as it cools to room temperature. At the same time, the chemical cure shrinkage exerts important influence on the total deformation. Due to the complexity and time consuming of the calculation, it is almost impossible for an industry to carry out the numerical simulation using viscoelastic property, which is the most close to the real material property of polymer material. However, finite element analysis (FEA) using temperature-dependent elastic property, temperature-dependent thermal expansion coefficient, and accurate chemical cure shrinkage can help to improve the accuracy on the stress and warpage prediction. This study has developed an evaluation method for the chemical cure shrinkage based on the measurement of the warpage of bimaterial model. The results show that FEA simulations without chemical cure shrinkage fail to accurately predict the package warpage. On the other hand, FEA simulations with chemical cure shrinkage are outlined, which show fair agreement with experimental measurements of package warpage over a range of temperatures. Furthermore, this study has evaluated the effect of silica filler percentage on the chemical cure shrinkage and confirmed that the chemical cure shrinkage decreases with the increase in silica filler percentage.
Nondestructive Failure Analysis and Simulation of Encapsulated 0402 Multilayer Ceramic Chip Capacitors Under Thermal and Mechanical Loading
Authors: Wunderle B. , Braun T. , May D. , Michel B. , Reichl H.
Published: February 2009

The use of multilayer ceramic chip capacitors as integrated passive in, e.g., system in package applications needs methods to examine and predict their reliability. Therefore, a nondestructive failure analytical technique is described to detect cracks in the ceramic and the metallic layers within encapsulated 0402 surface mount device (SMD) capacitors. After choosing from techniques to reproducibly generate cracks, it is shown that an in situ capacitance measurement is a convenient method to detect these failures unambiguously. Finite element simulations support the experimental results. A reliability estimate for capacitor integrity under given loading conditions is given.
Vibration Durability Assessment of Sn3.0Ag0.5Cu and Sn37Pb Solders Under Harmonic Excitation
Authors: Zhou Y. , Al-Bassyiouni M. , Dasgupta A.
Published: February 2009

In this paper, the vibration durability of both SAC305 and Sn37Pb interconnects are investigated with narrow-band harmonic vibration tests conducted at the first natural frequency of the test, printed wiring board, using constant-amplitude excitation. A time-domain approach, reported by Upadhyayula and Dasgupta (1998, “Guidelines for Physics-of-Failure Based Accelerated Stress Test,” Proceedings, Reliability and Maintainability Symposium, pp. 345–357), was adapted in this study for the fatigue analysis. The test board consists of daisy-chained components, to facilitate real-time failure monitoring. The response of the test specimens was characterized, and accelerated fatigue tests were conducted at different loading amplitudes to obtain a mix of low-cycle fatigue (LCF) and high-cycle fatigue data points. The SAC305 interconnects were found to have lower fatigue durability than comparable Sn37Pb interconnects, under the narrow-band harmonic excitation levels used in this study. This trend is consistent with most results from broadband vibration tests by Zhou et al. (2006, “Vibration Durability Comparison of Sn37Pb vs. SnAgCu Solders,” Proceedings of ASME International Mechanical Engineering Congress and Exposition, Chicago, IL, Paper No. 13555), Zhou and Dasgupta (2006, “Vibration Durability Investigation for SnPb and SnAgCu Solders With Accelerated Testing and Modeling,” IEEE-TC7 Conference on Accelerated Stress Testing & Reliability, San Francisco, CA), and Woodrow (2005, “JCAA/JG-PP No-Lead Solder Project: Vibration Test,” Boeing Electronics Materials and Processes Technical Report) and from repetitive mechanical shock tests by Zhang et al. (2005, “Isothermal Mechanical Durability of Three Selected Pb-Free Solders: Sn3.9Ag0.6Cu, Sn3.5Ag and Sn0.7Cu,” ASME J. Electron. Packag., 127, pp. 512–522), but counter to findings from quasistatic, LCF, and mechanical cycling studies by Cuddalorepatta and Dasgupta (2005, “Cyclic Mechanical Durability of Sn3.0Ag0.5Cu Pb-Free Solder Alloy,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Orlando, FL, Paper No. 81171). Failure analysis revealed two competing failure modes, one in the solder and another in the copper trace under the component. Thus solder fatigue properties extracted with the help of finite element simulation of the test article should be treated as lower-bound estimates of the actual fatigue curves.
Characterization of a fiber‐coupled luminescence dosimetry system for online in vivo dose verification during brachytherapy
Authors: Andersen Claus E. , Nielsen Søren Kynde , Greilich Steffen , Helt‐Hansen Jakob , Lindegaard Jacob Christian , Tanderup Kari
Published: February 2009

A prototype of a new dose‐verification system has been developed to facilitate prevention and identification of dose delivery errors in remotely afterloaded brachytherapy. The system allows for automatic online in vivo dosimetry directly in the tumor region using small passive detector probes that fit into applicators such as standard needles or catheters. The system measures the absorbed dose rate (0.1 s time resolution) and total absorbed dose on the basis of radioluminescence (RL) and optically stimulated luminescence (OSL) from aluminum oxide crystals attached to optical fiber cables (1 mm outer diameter). The system was tested in the range from 0 to 4 Gy using a solid‐water phantom, a Varian GammaMed Plus PDR afterloader, and dosimetry probes inserted into stainless‐steel brachytherapy needles. The calibrated system was found to be linear in the tested dose range. The reproducibility (one standard deviation) for RL and OSL measurements was 1.3%. The measured depth‐dose profiles agreed well with the theoretical expectations computed with the EGSNRC Monte Carlo code, suggesting that the energy dependence for the dosimeter probes (relative to water) is less than 6% for source‐to‐probe distances in the range of 2–50 mm. Under certain conditions, the RL signal could be greatly disturbed by the so‐called stem signal (i.e., unwanted light generated in the fiber cable upon irradiation). The OSL signal is not subject to this source of error. The tested system appears to be adequate for in vivo brachytherapy dosimetry.
A noninvasive eye fixation monitoring system for CyberKnife radiotherapy of choroidal and orbital tumors
Authors: Daftari I. K. , Petti P. L. , Larson D. A. , O'Brien J. M. , Phillips T. L.
Published: February 2009

A new noninvasive monitoring system for fixing the eye has been developed to treat orbital and choroidal tumors with CyberKnife‐based radiotherapy. This device monitors the eye during CT/MRI scanning and during treatment. The results of this study demonstrate the feasibility of the fixation light system for CyberKnife‐based treatments of orbital and choroidal tumors and supports the idea that larger choroidal melanomas and choroidal metastases could be treated with CyberKnife without implanting fiducial markers.
Integral dose conservation in radiotherapy
Authors: Reese Adam S. , Das Shiva K. , Curle Charles , Marks Lawrence B.
Published: February 2009

Treatment planners frequently modify beam arrangements and use IMRT to improve target dose coverage while satisfying dose constraints on normal tissues. The authors herein analyze the limitations of these strategies and quantitatively assess the extent to which dose can be redistributed within the patient volume. Specifically, the authors hypothesize that (1) the normalized integral dose is constant across concentric shells of normal tissue surrounding the target (normalized to the average integral shell dose), (2) the normalized integral shell dose is constant across plans with different numbers and orientations of beams, and (3) the normalized integral shell dose is constant across plans when reducing the dose to a critical structure. Using the images of seven patients previously irradiated for cancer of brain or prostate cancer and one idealized scenario, competing three‐dimensional conformal and IMRT plans were generated using different beam configurations. Within a given plan and for competing plans with a constant mean target dose, the normalized integral doses within concentric “shells” of surrounding normal tissue were quantitatively compared. Within each patient, the normalized integral dose to shells of normal tissue surrounding the target was relatively constant (1). Similarly, for each clinical scenario, the normalized integral dose for a given shell was also relatively constant regardless of the number and orientation of beams (2) or degree of sparing of a critical structure (3). 3D and IMRT planning tools can redistribute, rather than eliminate dose to the surrounding normal tissues (intuitively known by planners). More specifically, dose cannot be moved between shells surrounding the target but only within a shell. This implies that there are limitations in the extent to which a critical structure can be spared based on the location and geometry of the critical structure relative to the target.
Diagnostic detection of diffuse glioma tumors in vivo with molecular fluorescent probe‐based transmission spectroscopy
Authors: Gibbs‐Strauss Summer L. , O'Hara Julia A. , Srinivasan Subhadra , Hoopes P. Jack , Hasan Tayyaba , Pogue Brian W.
Published: February 2009

The diffuse spread of glioma tumors leads to the inability to image and properly treat this disease. The optical spectral signature of targeted fluorescent probes provides molecular signals from the diffuse morphologies of glioma tumors, which can be a more effective diagnostic probe than standard morphology‐based magnetic resonance imaging (MRI) sequences. Three orthotopic xenograft glioma models were used to examine the potential for transmitted optical fluorescence signal detection in vivo, using endogenously produced protoporphyrin IX (PpIX) and exogenously administered fluorescently labeled epidermal growth factor (EGF). Accurate quantification of the fluorescent signals required spectral filtering and signal normalization, and when optimized, it was possible to improve detection of sparse diffuse glioma tumor morphologies. The signal of endogenously produced PpIX provided similar sensitivity and specificity to MRI, while detection with fluorescently labeled EGF provided maximal specificity for tumors with high EGF receptor activity. Optical transmitted fluorescent signal may add significant benefit for clinical cases of diffuse infiltrative growth pattern glioma tumors given sufficient optimization of the signal acquisition for each patient.
A simple approach to using an amorphous silicon EPID to verify IMRT planar dose maps
Authors: Lee Christopher , Menk Fred , Cadman Patrick , Greer Peter B.
Published: February 2009

A simplified method of verifying intensity modulated radiation therapy (IMRT) fields using a Varian aS500 amorphous silicon electronic portal imaging device (EPID) is demonstrated. Unlike previous approaches, it does not involve time consuming or complicated analytical processing of the data. The central axis pixel response of the EPID, as well as the profile characteristics obtained from images acquired with a 6 MV photon beam, was examined as a function of field size. Ion chamber measurements at various depths in a water phantom were then collected and it was found that at a specific depth , the dose response and profile characteristics closely matched the results of the EPID analysis. The only manipulation required to be performed on the EPID images was the multiplication of a matrix of off axis ratio values to remove the effect of the flood field calibration. Similarly, was found for 18 MV. Planar dose maps at in a water phantom for a bar pattern, a strip pattern, and 14 clinical IMRT fields from two patient cases each being from a separate anatomical region, i.e., head and neck as well as the pelvis, for both energies were generated by the Pinnacle planning system (V7.4). EPID images of these fields were acquired and converted to planar dose maps and compared directly with the Pinnacle planar dose maps. Radiographic film dosimetry and a MapCHECK dosimetry device (Sun Nuclear Corporation, Melbourne, FL) were used as an independent verification of the dose distribution. Gamma analysis of the EPID, film, and Pinnacle planar dose maps generated for the clinical IMRT fields showed that approximately 97% of all points passed using a 3% dose/3mm DTA tolerance test. Based on the range of fields studied, the author's results appear to justify using this approach as a method to verify dose distributions calculated on a treatment planning system, including complex intensity modulated fields.
JPEG2000 3D compression vs 2D compression: An assessment of artifact amount and computing time in compressing thin‐section abdomen CT images
Authors: Kim Bohyoung , Lee Kyoung Ho , Kim Kil Joong , Richter Thomas , Kang Heung‐Sik , Kim So Yeon , Kim Young Hoon , Seo Jinwook
Published: February 2009

To assess the advantages of the Joint Photographic Experts Group (JPEG)2000 3D (part 2) over JPEG2000 in compressing thin‐section abdomen CT data sets, 60 thin‐section (0.67 mm) scans from 35 males and 25 females, ranging from 23 to 95 years of age (mean, 58 years), were compressed reversibly (as a negative control) and irreversibly to 4:1, 6:1, 8:1, 10:1, and 12:1 using JPEG2000 3D and JPEG2000 algorithms. Encoding and decoding times and peak signal‐to‐noise ratios (PSNRs) were measured. For 60 (one image per scan) representative sections containing abnormalities, three radiologists independently compared original and compressed images and graded compression artifacts as 0 (none, indistinguishable), 1 (barely perceptible), 2 (subtle), or 3 (significant). According to pooled radiologists’ responses, the range of visually lossless threshold (VLT, the highest compression ratio at which a compressed image is indistinguishable from its original) was determined as one of , 4:1–6:1, 6:1–8:1, 8:1–10:1, 10:1–12:1, and . Wilcoxon signed rank tests and exact tests for paired proportions were used for the comparisons between the two compressions. At each irreversible compression ratio, compared to JPEG2000, JPEG2000 3D required two‐ or threefold greater computing times and introduced less artifacts in terms of PSNR and the grade ( at 6:1 or higher) and the presence of perceived artifacts (, at 6:1 for all readers and at 8:1 for two readers). According to PSNR and readers’ responses, 6:1 and 8:1 JPEG2000 3D compressions showed more artifacts than 4:1 and 6:1 JPEG2000 compressions, respectively, and 10:1 and 12:1 JPEG2000 3D compressions showed similar artifacts to those of 8:1 and 10:1 JPEG2000 compressions, respectively. The determined VLT range was higher for JPEG2000 3D than for JPEG2000 : the 3D compression showed the VLT ranges of 4:1–6:1, 6:1–8:1, and 8:1–10:1 for 24 (40%), 30 (50%), and 6 (10%) of the 60 original images, respectively, while the 2D compression showed the VLT ranges of , 4:1–6:1, and 6:1–8:1 for 1 (1.7%), 40 (66.7%), and 19 (31.6%) images, respectively. Compared to JPEG2000, JPEG2000 3D increased the VLT range in 23 of the 60 original images by one or two ranges , while the remaining 37 images had the same VLT range between the two compressions. In conclusion, compared to JPEG2000 compression, JPEG2000 3D compression yields less artifacts in compressing thin‐section abdomen CT images but requires significantly greater computing times. For the tested data set compressed to the range from 4:1 to 12:1, JPEG2000 3D could increase compression level reasonably (by 2 or less in terms of compression ratio) compared to JPEG2000 for the same amount of artifacts.
Application‐ and patient size‐dependent optimization of x‐ray spectra for CT
Authors: Kalender Willi A. , Deak Paul , Kellermeier Markus , van Straten Marcel , Vollmar Sabrina V.
Published: February 2009

Although x‐ray computed tomography (CT) has been in clinical use for over 3 decades, spectral optimization has not been a topic of great concern; high voltages around 120 kV have been in use since the beginning of CT. It is the purpose of this study to analyze, in a rigorous manner, the energies at which the patient dose necessary to provide a given contrast‐to‐noise ratio (CNR) for various diagnostic tasks can be minimized. The authors used cylindrical water phantoms and quasianthropomorphic phantoms of the thorax and the abdomen with inserts of 13 mm diameter mimicking soft tissue, bone, and iodine for simulations and measurements. To provide clearly defined contrasts, these inserts were made of solid water with a 1% difference in density (DD) to represent an energy‐independent soft‐tissue contrast of 10 Hounsfield units (HU), calcium hydroxyapatite (Ca) representing bone, and iodine (I) representing the typical contrast medium. To evaluate CT of the thorax, an adult thorax phantom plus extension rings up to a size of to mimic different patient cross sections were used. For CT of the abdomen, we used a phantom of and an extension ring of . The CT scanner that the authors used was a SOMATOM Definition (Siemens Healthcare, Forchheim, Germany) at 80, 100, 120, and 140 kV. Further voltage settings of 60, 75, 90, and 105 kV were available in an experimental mode. The authors determined contrast for the density difference, calcium, and iodine, and noise and 3D dose distributions for the available voltages by measurements. Additional voltage values and monoenergetic sources were evaluated by simulations. The dose‐weighted contrast‐to‐noise ratio (CNRD) was used as the parameter for optimization. Simulations and measurements were in good agreement with respect to absolute values and trends regarding the dependence on energy for the parameters investigated. For soft‐tissue imaging, the standard settings of 120–140 kV were found as adequate choices with optimal values increasing for larger cross sections, e.g., for large abdomens voltages higher than 140 kV may be indicated. For bone and iodine imaging the optimum values were generally found at significantly lower voltages of typically below 80 kV. This offers a potential for dose reduction of up to 50%, but demands significantly higher power values in most cases. The authors concluded that voltage settings in CT should be varied more often than is common in practice today and should be chosen not only according to patient size but also according to the substance imaged in order to minimize dose while not compromising image quality. A reduction from 120 to 80 kV, for example, would yield a reduction in patient dose by more than half for coronary CT angiography. The use of lower voltages has to be recommended for contrast medium studies in cardiac and pediatric CT.
Evaluation of clinical image processing algorithms used in digital mammography
Authors: Zanca Federica , Jacobs Jurgen , Van Ongeval Chantal , Claus Filip , Celis Valerie , Geniets Catherine , Provost Veerle , Pauwels Herman , Marchal Guy , Bosmans Hilde
Published: February 2009

Screening is the only proven approach to reduce the mortality of breast cancer, but significant numbers of breast cancers remain undetected even when all quality assurance guidelines are implemented. With the increasing adoption of digital mammography systems, image processing may be a key factor in the imaging chain. Although to our knowledge statistically significant effects of manufacturer‐recommended image processings have not been previously demonstrated, the subjective experience of our radiologists, that the apparent image quality can vary considerably between different algorithms, motivated this study. This article addresses the impact of five such algorithms on the detection of clusters of microcalcifications. A database of unprocessed (raw) images of 200 normal digital mammograms, acquired with the Siemens Novation DR, was collected retrospectively. Realistic simulated microcalcification clusters were inserted in half of the unprocessed images. All unprocessed images were subsequently processed with five manufacturer‐recommended image processing algorithms (Agfa Musica 1, IMS Raffaello Mammo 1.2, Sectra Mamea AB Sigmoid, Siemens OPVIEW v2, and Siemens OPVIEW v1). Four breast imaging radiologists were asked to locate and score the clusters in each image on a five point rating scale. The free‐response data were analyzed by the jackknife free‐response receiver operating characteristic (JAFROC) method and, for comparison, also with the receiver operating characteristic (ROC) method. JAFROC analysis revealed highly significant differences between the image processings (, ), suggesting that image processing strongly impacts the detectability of clusters. Siemens OPVIEW2 and Siemens OPVIEW1 yielded the highest and lowest performances, respectively. ROC analysis of the data also revealed significant differences between the processing but at lower significance (, ) than JAFROC. Both statistical analysis methods revealed that the same six pairs of modalities were significantly different, but the JAFROC confidence intervals were about 32% smaller than ROC confidence intervals. This study shows that image processing has a significant impact on the detection of microcalcifications in digital mammograms. Objective measurements, such as described here, should be used by the manufacturers to select the optimal image processing algorithm.
LocalBorrelia burgdorferisensu stricto andBorrelia afzeliistrains in a single mixed antigen improves western blot sensitivity: Table 1
Authors: Mavin S , Evans R , Milner R M , Chatterton J M W , Ho-Yen D O
Published: February 2009

Aims:

This study evaluates the use of localBorrelia burgdorferisensu stricto andBorrelia afzeliistrains in a single mixed antigen for in-house IgG western blots in the routine diagnostic setting by comparing it with the current in-house protocol.

Methods:

Sera from 233 patients from areas of Scotland with low and high prevalence for Lyme borreliosis were tested by western blots prepared from reference strain antigen (B burgdorferisensu stricto) and mixed antigen (B burgdorferisensu stricto andB afzelii). Results were scored using original and revised criteria, and results were compared.

Results:

The mixed antigen produced significantly more bands than the reference antigen. Using the original interpretation criteria the mixed antigen produced more positive results than the reference antigen (90 versus 85). When the revised criteria were applied to the mixed antigen there were 14 more patients with positive results than with the reference antigen (99 versus 85); this difference was significant. Although 22 patients were positive with the mixed antigen and revised criteria, but negative/equivocal with the reference antigen, eight patients who were positive with reference antigen remained negative with the mixed antigen. The positive predictive value of the two antigen preparations was the same (96%). The negative predictive value of the mixed antigen with revised criteria was higher than the reference antigen (96% versus 88%), but the specificity was similar (97% versus 98%).

Conclusions:

The mixed antigen and revised interpretation criteria have been successfully incorporated into the routine diagnostic testing service, increasing the sensitivity of the in-house IgG western blot test for Scottish patients.
Acid phosphatases of Ipomoea sp. cultured in vitro. 2. Influence of gibberellic acid on the formation of phosphatases
Authors: Zink M.W.
Published: February 2009

The levels and developmental patterns of the two acid phosphatases in the two strains of Ipomoea sp. (morning glory) grown in vitro are influenced differently by gibberellic acid (GA3). In the strain that requires a number of exogenously added hormones for growth (original strain), GA3 appears to show little effect on the specific activity of the phosphatases during the initial 3 days of growth but represses their levels in the growth medium, soluble and particulate fractions upon further growth. The repressive effect of both inorganic phosphate and GA3 on the enzymes appears to be additive. In the strain that does not require exogenously added hormones for growth (NH strain), the level of enzymes in the soluble fraction increases in the presence of GA3 during the early stages of growth and then decreases with culture age. GA3 also elevates the level of the enzymes in the particulate fraction over that in the controls. This elevation increases as phosphate level in the medium is increased. However, GA3 greatly decreases secretion, or leaching of the enzymes from the cells.
Resource limitation of fruit and seed production in some Asclepias species
Authors: Willson Mary F. , Price Peter W.
Published: February 2009

Effects of modifying resource availability were studied on three species of milkweed, Asclepias syriaca, A. verticillata, and A. incarnata. The influence of mineral fertilizer, leaf removal, and shading were investigated to test the hypothesis that milkweed species are resource limited. Addition of mineral fertilizer resulted in increased numbers of mature pods per stem in A. syriaca and A. verticillata, and numbers of seeds per pod and seed weight in A. syriaca. Defoliation tended to result in a reduction of number of mature pods produced per stem. Results from shading showed a similar trend but few significant differences were observed.
LONG-TIME ASYMPTOTICS OF THE TODA LATTICE FOR DECAYING INITIAL DATA REVISITED
Authors: KRÜGER HELGE , TESCHL GERALD
Published: February 2009

The purpose of this article is to give a streamlined and self-contained treatment of the long-time asymptotics of the Toda lattice for decaying initial data in the soliton and in the similarity region via the method of nonlinear steepest descent.
FINDING GALOIS REPRESENTATIONS CORRESPONDING TO CERTAIN HECKE EIGENCLASSES
Authors: DEWITT MEGHAN , DOUD DARRIN
Published: February 2009

In 1992, Ash and McConnell presented computational evidence of a connection between three-dimensional Galois representations and certain arithmetic cohomology classes. For some examples, they were unable to determine the attached representation. For several Hecke eigenclasses (including one for which Ash and McConnell did not find the Galois representation), we find a Galois representation which appears to be attached and show strong evidence for the uniqueness of this representation. The techniques that we use to find defining polynomials for the Galois representations include a targeted Hunter search, class field theory and elliptic curves.
STRINGS OF CONSECUTIVE PRIMES IN FUNCTION FIELDS
Authors: TANNER NOAM
Published: February 2009

In a recent paper, Thorne [5] proved the existence of arbitrarily long strings of consecutive primes in arithmetic progressions in the polynomial ring 𝔽q[t]. Here we extend this result to show that given any k there exists a string of k consecutive primes of degree D in arithmetic progression for all sufficiently large D.
THE NUMBER OF REPRESENTATIONS OF A POSITIVE INTEGER BY CERTAIN QUATERNARY QUADRATIC FORMS
Authors: ALACA AYŞE , ALACA ŞABAN , LEMIRE MATHIEU F. , WILLIAMS KENNETH S.
Published: February 2009

Some theta function identities are proved and used to give formulae for the number of representations of a positive integer by certain quaternary forms x2 + ey2 + fz2 + gt2 with e, f, g ∈ {1, 2, 4, 8}.
GENERATING FUNCTIONS FOR HECKE OPERATORS
Authors: AL HAJJ SHEHADEH HALA , JAAFAR SAMAR , KHURI-MAKDISI KAMAL
Published: February 2009

Fix a prime N, and consider the action of the Hecke operator TN on the space [Formula: see text] of modular forms of full level and varying weight κ. The coefficients of the matrix of TN with respect to the basis {E4i E6j | 4i + 6j = κ} for [Formula: see text] can be combined for varying κ into a generating function FN. We show that this generating function is a rational function for all N, and present a systematic method for computing FN. We carry out the computations for N = 2, 3, 5, and indicate and discuss generalizations to spaces of modular forms of arbitrary level.
Chemoinformatics—an introduction for computer scientists
Authors: Brown Nathan
Published: February 2009

Chemoinformatics is an interface science aimed primarily at discovering novel chemical entities that will ultimately result in the development of novel treatments for unmet medical needs, although these same methods are also applied in other fields that ultimately design new molecules. The field combines expertise from, among others, chemistry, biology, physics, biochemistry, statistics, mathematics, and computer science. In this general review of chemoinformatics the emphasis is placed on describing the general methods that are routinely applied in molecular discovery and in a context that provides for an easily accessible article for computer scientists as well as scientists from other numerate disciplines.