bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of Pancreatic β-Cell Death in Type 1 and Type 2 Diabetes
Authors: Cnop Miriam , Welsh Nils , Jonas Jean-Christophe , Jörns Anne , Lenzen Sigurd , Eizirik Decio L.
Published: March 2007

Type 1 and type 2 diabetes are characterized by progressive β-cell failure. Apoptosis is probably the main form of β-cell death in both forms of the disease. It has been suggested that the mechanisms leading to nutrient- and cytokine-induced β-cell death in type 2 and type 1 diabetes, respectively, share the activation of a final common pathway involving interleukin (IL)-1β, nuclear factor (NF)-κB, and Fas. We review herein the similarities and differences between the mechanisms of β-cell death in type 1 and type 2 diabetes. In the insulitis lesion in type 1 diabetes, invading immune cells produce cytokines, such as IL-1β, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ. IL-1β and/or TNF-α plus IFN-γ induce β-cell apoptosis via the activation of β-cell gene networks under the control of the transcription factors NF-κB and STAT-1. NF-κB activation leads to production of nitric oxide (NO) and chemokines and depletion of endoplasmic reticulum (ER) calcium. The execution of β-cell death occurs through activation of mitogen-activated protein kinases, via triggering of ER stress and by the release of mitochondrial death signals. Chronic exposure to elevated levels of glucose and free fatty acids (FFAs) causes β-cell dysfunction and may induce β-cell apoptosis in type 2 diabetes. Exposure to high glucose has dual effects, triggering initially “glucose hypersensitization” and later apoptosis, via different mechanisms. High glucose, however, does not induce or activate IL-1β, NF-κB, or inducible nitric oxide synthase in rat or human β-cells in vitro or in vivo in Psammomys obesus. FFAs may cause β-cell apoptosis via ER stress, which is NF-κB and NO independent. Thus, cytokines and nutrients trigger β-cell death by fundamentally different mechanisms, namely an NF-κB–dependent mechanism that culminates in caspase-3 activation for cytokines and an NF-κB–independent mechanism for nutrients. This argues against a unifying hypothesis for the mechanisms of β-cell death in type 1 and type 2 diabetes and suggests that different approaches will be required to prevent β-cell death in type 1 and type 2 diabetes.
Transcriptional profiling of subjects from the Iowa adoption studies
Authors: Philibert Robert A. , Ryu Gi‐Yung , Yoon Jae‐Geun , Sandhu Harinder , Hollenbeck Nancy , Gunter Tracy , Barkhurst Amanda , Adams William , Madan Anup
Published: March 2007

Transcriptional profiling has been used to identify gene expression patterns indicative of general medical illnesses such as atherosclerosis. However, whether these methods can identify common psychiatric disorders has not been established. To answer this question with respect to nicotine use, we used genome‐wide expression profiling lymphoblast cell lines from six actively smoking Iowa Adoption Studies (IAS) subjects and nine “clean” control subjects, followed by real‐time PCR (RT‐PCR) of gene expression patterns in lymphoblast derived RNA from 94 subjects in the IAS. As compared to those from controls without a history of smoking (n = 9), the expression levels of 579 of 29,098 genes were significantly up‐regulated and expression levels of 584 of 29,098 genes were significantly down‐regulated in lymphoblast lines from currently smoking subjects (n = 6). RT‐PCR confirmation of four select RNA levels confirmed the validity of the overall profile and revealed highly significant relationships between the expression of some of these transcripts and (1) major depression, (2) antisocial personality, (3) nicotine dependence, and (4) cannabis dependence. We conclude that the use of expression profiling may contribute significant insights into the biology of complex behavioral disorders. © 2007 Wiley‐Liss, Inc.
Biological relationship between central and South American Chibchan speaking populations: Evidence from mtDNA
Authors: Melton Phillip E. , Briceño I. , Gómez A. , Devor E.J. , Bernal J.E. , Crawford M.H.
Published: March 2007

We examined mitochondrial DNA (mtDNA) haplogroup and haplotype diversity in 188 individuals from three Chibchan (Kogi, Arsario, and Ijka) populations and one Arawak (Wayuú) group from northeast Colombia to determine the biological relationship between lower Central American and northern South American Chibchan speakers. mtDNA haplogroups were obtained for all individuals and mtDNA HVS‐I sequence data were obtained for 110 samples. Resulting sequence data were compared to 16 other Caribbean, South, and Central American populations using diversity measures, neutrality test statistics, sudden and spatial mismatch models, intermatch distributions, phylogenetic networks, and a multidimensional scaling plot. Our results demonstrate the existence of a shared maternal genetic structure between Central American Chibchan, Mayan populations and northern South American Chibchan‐speakers. Additionally, these results suggest an expansion of Chibchan‐speakers into South America associated with a shift in subsistence strategies because of changing ecological conditions that occurred in the region between 10,000–14,000 years before present. Am J Phys Anthropol, 2007. © 2007 Wiley‐Liss, Inc.
Carbon nanotubes‐reinforced PET nanocomposite by melt‐compounding
Authors: Anand K Anoop , Agarwal U. S. , Joseph Rani
Published: March 2007

Poly(ethylene terephthalate) (PET) nanocomposites with single‐walled carbon nanotubes (SWNTs) have been prepared by a simple melt compounding method. With increasing concentration (0–3 wt %) of SWNTs, the mechanical and dynamic mechanical properties improved, corresponding to effective reinforcement. Melt rheological characterization indicated the effective entanglements provided by SWNTs in the melt state as well. Thermogravimetric analysis suggested no influence of SWNTs on the thermal stability of PET. Electrical conductivity measurements on the composite films pointed out that the melt compounded SWNTs can result in electrical percolation albeit at concentrations exceeding 2 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation of grafted copolymers via oxidized polypropylene
Authors: Dang V. , Fezza R. , Shu C. , Phan T. , Song C.
Published: March 2007

A new and novel class of oxidized polypropylene containing bound peroxide functionalities can be used as polymerization initiators to produce polypropylene‐grafted copolymers. Upon heat treatment, the peroxide functionalities in the oxidized polypropylene act as a source of free radicals, reacting with the unsaturated double bonds of the monomer and initiating polymerization. The grafting reaction is carried out in the solid state in a reactor. The advantage of grafting via this new class of oxidized polypropylene is the elimination of expensive and environmentally unfriendly organic peroxides. A number of monomers have been grafted using oxidized polypropylene, including vinyl acetate, vinyl pyrrolidinone, methacrylic anhydride, and maleic anhydride. Oxidized polypropylene‐grafted copolymers are effective compatibilizers for PP/ETP blends and good coupling agents in glass‐ reinforced formulations. Preparation, characterization, and mechanical properties of terpolymers prepared from sequential grafting of oxidized polypropylene are also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Effect of poly(ethylene‐co‐glycidyl methacrylate) compatibilizer content on the morphology and physical properties of ethylene vinyl acetate–wood fiber composites
Authors: Dikobe D. G. , Luyt A. S.
Published: March 2007

In this study, ethylene vinyl acetate (EVA)–wood fiber (WF) (uncompatibilized) and EVA/poly(ethylene‐co‐glycidyl methacrylate) (EGMA)‐WF (compatibilized) were blended, and their morphology as well as mechanical, thermal, O2 permeability, and water absorption properties were investigated. It is shown that there is a possible interaction between EVA and WF. This interaction seems to be very weak, and the resulting composites have poor properties. The presence of EGMA in the composite improved most of the investigated properties. IR analysis shows that there is a grafting reaction between EGMA and WF. The resulting composites have better properties than EVA or its uncompatibilized composites. The amount of compatibilizer has an effect on the properties of the composites. The mechanical properties improved with increasing EGMA content, but thermal stability decreased with increasing EGMA content. Oxygen permeability and water absorption decreased with an increase in EGMA content in the composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Die Bicentenario‐Chiloe‐Brücke: Seismische und dynamische Untersuchungen
Authors: Sadegh‐Azar Hamid
Published: March 2007

In diesem Beitrag wird die seismische und dynamische Analyse der Bicentenario‐Chiloe‐Brücke in Chile präsentiert. Die Brücke soll den Chacao‐Kanal (Canal De Chacao) überqueren und die Insel Chiloe mit dem Chilenischen Festland verbinden. Der vorgesehene Standort der Brücke liegt in einer der seismisch aktivsten und höchst gefährdeten Zonen der Welt. In unmittelbarer Umgebung wurde das bisher stärkste Erdbeben der Welt registriert (Valdivia‐Erdbeben von 1960 mit einer Magnitude von 9.5). Die Bemessung der Hängebrücke wird somit maßgeblich durch den Lastfall Erdbeben beeinflußt. Die besondere Herausforderung hierbei ist die genaue Berücksichtigung des Einflusses des Baugrunds auf die seismische Einwirkung und die konsistente Erfassung der Boden‐Brücken‐Wechselwirkung. In diesem Aufsatz werden einige wichtige Aspekte und Probleme der seismischen Analyse einer solchen Hängebrücke dargestellt und Lösungswege dafür aufgezeigt. Hierbei wird versucht, die teilweise etwas komplizierten Berechnungsmethoden durch verständliche Formulierungen vereinfacht darzustellen, so daß der Aufsatz für den praktizierenden Ingenieur verständlich bleibt.
Synthesis of (S)‐2‐Ethoxy‐3‐Phenylpropanoic Acid Derivatives and Their Insulin‐Sensitizing Activity
Authors: Wu Ying‐Hua
Published: March 2007

A series of (S)‐2‐ethoxy‐3‐phenylpropanoic acid derivatives were synthesized and their insulin‐sensitizing activities were evaluated in 3T3‐L1 cells. Compounds 1b, 1d, 1e and 1f exhibited more potent insulin‐sensitizing activity than rosiglitazone.
Substituent Effect on N‐Benzylideneanilines by DFT Energy Partition
Authors: Ma Yan‐Ping , Bao Peng , Yu Zhong‐Heng
Published: March 2007

To investigate the substituent effect on π‐electron delocalization of the N‐benzylideneaniline (NBA), the vertical resonance energies ΔEV(θ) of eleven substituted NBAs were separated into π and σ parts at the B3LYP/6‐311G(d) level of the Density Functional Theory (DFT). When substituted with an electron‐releasing group –OH, the calculated ΔEV(θ) of NBA was increased, indicative of more resonance destabilization than the mother molecule. However, when substituted with an electron‐withdrawing group –NO2, the calculated ΔEV(θ) values indicated less resonance destabilization. The most destabilizing effect was observed especially when the
–OH group located at the ortho‐position of the aromatic ring in the fragment –NCH–Ar. For most of the substituted NBA molecules, it was the destabilized σ framework that determined the destabilizing feature of the vertical resonance energy, instead of the stabilized π system. When the –NO2 substituent at the para‐position of the aromatic ring of the –NCH–Ar group, the π system had the highest stabilizing effect while the ( framework exhibited the highest destabilizing effect. While the –NO2 substituent was at the para‐position of the left aromatic ring (Ar–), the NBA had the least vertical resonance energy value.
Study on the Supramolecular Interaction of β‐Cyclodextrin with Gemfibrozil by Spectrofluorimetry and Its Analytical Application
Authors: Huang Hui , Liu Fang , Jia Bao‐Xiu , Xu Ke‐Hua , Chen Zhen‐Zhen , Tang Bo
Published: March 2007

The supramolecular interaction of gemfibrozil with β‐cyclodextrin (β‐CD) was studied by spectrofluorimetry. The mechanism of the inclusion was discussed by spectrofluoremetry, infrared spectrum and 1H NMR spectrum. The results showed that a 1:1 (β‐CD:gemfibrozil) complex was formed with an apparent association constant of 3.844×103 L·mol−1. Based on the enhancement of the fluorescent intensity of gemfibrozil, a spectrofluorimetric method for the determination of gemfibrozil in bulk aqueous solution in the presence of β‐CD was developed. The linear range was 3.30 ng·mL−1–6.00 µg·mL−1 with the detection limit of 0.980 ng·mL−1. There was no interference from the excipients normally used in tablet composition and the serum main compositions. The proposed method was then successfully applied to the determination of gemfibrozil in capsules and serum.
A Novel Electrogenerated Chemiluminescence Reaction Scheme Using Core‐Shell Luminol‐Based SiO2 Nanoparticles as a Regulator and Its Analytical Application
Authors: Zhang Li‐Li , Zheng Xing‐Wang , Guo Zhi‐Hui
Published: March 2007

A novel core‐shell luminol‐based SiO2 nanoparticle was synthesized by two step micro‐emulsion method. While these nanoparticles were used as electrogenerated chemiluminescence (ECL) reagent, the electrochemical (EC) reaction as well as the subsequent chemiluminescence (CL) reaction not only could be separated spatially, but also presented high efficiency for analytical purpose. In this case, the core‐shell luminol‐based SiO2 nanoparticles offered more potential to avoid the contradiction between the EC and the CL reaction conditions. A new ECL method based on the nanoparticle was developed, and isoniazid was selected as a model analyte to illustrate the characteristics of this new ECL method. Under the selected conditions, the proposed ECL response to isoniazid concentration was linear in the range of 1.0×10−10 to 1.0×10−6 g/mL with 2×10−11 g/mL detection limit.
Highly Efficient One‐Pot Synthesis of 2‐Arylmethyl N‐Substituted Anilines via Yb(OTf)3 Catalyzed Three‐Component Reaction
Authors: Wang Li‐Min , Zhang Liang , Hu Liang , Tian He
Published: March 2007

An efficient method has been developed for one‐pot three‐component coupling reactions of various aldehydes, 1‐cyclohexen‐2‐one, and primary or secondary amines in the presence of a catalytic amount of Yb(OTf)3 under mild conditions to afford the corresponding 2‐arylmethyl N‐substituted anilines in good yields. In addition, the catalyst was easily recovered and could be reused for at least four cycles without any loss of activity.
Synthesis and Enantioselective Discrimination of Chiral Fluorescence Receptors Bearing Amino Acid Units
Authors: Xu Kuo‐Xi , He Yong‐Bing , Qing Guang‐Yan , Qin Hai‐Juan , Liu Shun‐Ying , Meng Ling‐Zhi
Published: March 2007

Two chiral fluorescence receptors (1, 2) were synthesized, and their structures were characterized by IR, 1H NMR, 13C NMR, mass spectra and elemental analysis. The chiral recognition of receptors was studied by 1H NMR and fluorescence spectra. The results demonstrate that receptors and dibenzoyl tartrate anion formed a 1:1 complex. The receptor 1 exhibited a good enantioselective recognition ability toward the enantiomers of dibenzoyl tartrate anion.
Calculation of Nuclear Spin Relaxation Times
Authors: L. Sudmeier James , E. Anderson Stanley , S. Frye James
Published: March 2007

This paper summarizes the equations for calculating nuclear spin relaxation times and nuclear Overhauser effects. The relaxation equations deal with the dipolar, quadrupolar, scalar, chemical shift anisotropy, paramagnetic, and spin‐rotation mechanisms for the simplest case of isotropic reorientation of rigid molecules. All equations are defined using consistent units, showing the similarities among various terms and giving numerical examples.
The use of freely diffusible, NMR‐detectable tracers for measuring organ perfusion
Authors: Neil Jeffrey J.
Published: March 2007

The application of NMR techniques to tracer methods for measuring organ perfusion is a relatively recent development. The general theory for measurement of organ perfusion after the administration of exogenous, freely diffusible tracers is discussed with special attention to NMR‐detectable tracers. Different routes of tracer administration are available and are presented in the context of the effect of route of administration on data analysis. A review of the recent literature validating the use of deuterium and fluorine as NMR flow tracers is provided.
Nuclear magnetic resonance measurements of intracellular pH: Biomedical implications
Authors: Malhotra Deepak , Shapiro Joseph I.
Published: March 2007

The measurement of intracellular pH is of crucial importance in biomedical investigation. Nuclear magnetic resonance (NMR) spectroscopy methods allow investigators to monitor this essential parameter in a variety of experimental conditions. Although a number of NMR spectroscopy methods for measuring intracellular pH have been described, the method of using the chemical shift of inorganic phosphate has been employed most widely. In this review, we discuss the various NMR methodologies which allow for measurement of intracellular pH as well as selected topics where these measurements have been employed. Because of the volume of work which has been published using NMR to monitor intracellular pH, we have not attempted to be exhaustive in our review, but rather have tried to highlight the importance of this methodology by reviewing several topics in biology and medicine where NMR measurements of intracellular pH have played an important role in improving our understanding.
PD‐L1 (B7‐H1) expression by urothelial carcinoma of the bladder and BCG‐induced granulomata
Authors: Inman Brant A. , Sebo Thomas J. , Frigola Xavier , Dong Haidong , Bergstralh Eric J. , Frank Igor , Fradet Yves , Lacombe Louis , Kwon Eugene D.
Published: March 2007

BACKGROUND

PD‐L1 (programmed death ligand 1, B7‐H1) is a cell surface glycoprotein that can impair T‐cell function. PD‐L1 is aberrantly expressed by multiple human malignancies and has been shown to carry a highly unfavorable prognosis in patients with kidney cancer. The role of PD‐L1 was evaluated as a mechanism for local stage progression in urothelial carcinoma (UC) of the bladder.

METHODS

Using immunohistochemistry, PD‐L1 expression was evaluated in a cohort of 280 high‐risk UCs of the bladder. PD‐L1 was modeled as a predictor of bladder cancer stage using ordinal logistic regression. Other covariates evaluated as potential confounders included age, gender, tumor grade, and lymphocytic infiltration. Further, PD‐L1 was evaluated as a potential mechanism of bacillus Calmette‐Guerin (BCG) failure in the subset of high‐risk nonmuscle‐invasive tumors that received this treatment.

RESULTS

PD‐L1 expression was observed in 7% of pTa, 16% of pT1, 23% of pT2, 30% of pT3/4, and 45% of carcinoma in situ (CIS) tumors. PD‐L1 expression was associated with high‐grade tumors (odds ratio [OR] = 2.4, P = .009) and tumor infiltration by mononuclear cells (OR = 5.5, P = .004). We observed that the key determinants of stage progression in this cohort were World Health Organization/International Society of Urologic Pathology (WHO/ISUP) high‐grade tumor pathology (OR = 4.77, 95% confidence interval [CI]: 2.73–8.34; P < .001) and PD‐L1 expression (OR = 2.20, P = .012). PD‐L1 expression was found to be extremely abundant in the BCG‐induced bladder granulomata in 11 of 12 patients failing BCG treatment.

CONCLUSIONS

Collectively, these data indicate that tumor PD‐L1 may facilitate localized stage‐advancement of UC and attenuate responses to BCG immunotherapy by neutralizing T cells that normally guard against cancer invasion from the epithelium into the bladder musculature. Cancer 2007. © 2007 American Cancer Society.
Characterization of Pericyclic Reactions Using Multicenter Electron Delocalization Analysis
Authors: Mandado Marcos , González‐Moa María J. , Mosquera Ricardo A.
Published: March 2007

This work investigates the applicability of multicenter delocalization analysis to the characterization of pericyclic reactions. The results indicate that multicenter delocalization indices are a powerful tool for studying concerted processes, allowing the characterization of aromatic transition states with a significant increase in the electron delocalization. Moreover, an advantage over magnetic‐based indices is that multicenter delocalization indices are not influenced by local electron currents but by the electron delocalization along the multiple (n) centers, and provide, in a quantitative sense, more reliable results. A thorough comparison with magnetic‐based indices is carried out for the trimerization reaction of acetylene. Tracking the values of multicenter delocalization indices along the reaction path allows investigation of the nature of concerted mechanisms. Six‐center electron delocalization displays a maximum at the transition state of the Diels–Alder reaction, whereas a similar maximum of four‐center electron delocalization is slightly displaced to butadiene for the ring opening of cyclobutene. The profile of multicenter electron delocalization indices along the reaction path of [2+2] cycloaddition of ketene to ethene shows the presence of the two independent mechanisms that agree with the two HOMO/LUMO orbital interactions previously proposed to dominate this reaction.
Pivotal Steps Towards Quantification of Molecular Diffusion Coefficients by NMR
Authors: Zhang Shanmin
Published: March 2007

Using nuclear magnetic resonance (NMR) spectroscopy with a pair of pulsed field gradients (PFGs), Stajeskal and Tanner successfully measured molecular diffusion coefficients in solution in 1965. This method has since been used extensively in various applications, especially after the PFG was implemented in commercial NMR probes. Due to the nonuniformity of the PFG and radio frequency (RF) fields, molecules distributed throughout the sample experience different PFG and RF fields and contribute unevenly to the measured diffusion coefficients, resulting in considerable errors in conventional NMR diffusion experiments. By selective excitation of a central sample region with an offset‐independent adiabatic inversion pulse and a PFG, a uniform RF field can be assumed, and the PFG can be represented as a linear approximation. Under these conditions, the molecules diffuse as if they were all experiencing the same effective gradient ge, leading to a Gaussian signal decay as a function of the PFG strength. Quantitative measurement of molecular diffusion coefficients is therefore made possible. From the diffusion coefficient of a 90 % H2O/10 % D2O sample, it is convenient to calibrate ge with a Java program. In a similar way the nonlinearity of the PFG can be corrected.
Recovery of boron from borax sludge using solid–liquid extraction followed by ion exchange with amberlite resin
Authors: Özdemir Mine , Kıpçak İlker
Published: March 2007

To recover boron from borax sludge, initially solid–liquid extraction with dilute sulfuric acid was utilized in a batch reactor. The optimum working conditions for boron extraction were determined. A maximum extraction yield of 85.0% for boron was obtained. In the process, 9.14% of the calcium and 16.8% of the magnesium contained in the solid waste passed to the extraction solution. Subsequently, batch ion‐exchange studies were performed using Amberlite IRA‐743‐boron specific resin for the separation of boron from the calcium and magnesium components in the extraction solution. The effects of contact time and resin dosage on the ion‐exchange process were investigated. A second order kinetic model seemed to be appropriate for the boron ion‐exchange. The boron, which was sorbed on the resin, was eluted completely using a 0.5 M sulfuric acid solution. It was seen that the calcium and magnesium components were not present in the elution solution. In this process, boron was successfully separated from the calcium and magnesium species. It was determined that approximately 98.70% of the boron in the extraction solution could be recovered at a pH value of 8, a contact time of 24 h, an initial boron concentration of 500 mg/L, a resin dosage of 2.5 g of resin/50 mL of extraction solution, and a temperature of 25°C. © 2007 American Institute of Chemical Engineers Environ Prog, 2007
The effect of single vegetation elements on wind speed and sediment transport in the Sahelian zone of Burkina Faso
Authors: Leenders J. K. , Boxel J. H. van , Sterk G.
Published: March 2007

Soil loss caused by wind erosion is a widespread phenomenon in the Sahelian zone of West Africa. According to Sahelian farmers, scattered vegetation standing in amongst the crop has the potential for a wind erosion control strategy. This study was conducted to study the effect of single vegetation elements on the pattern of average wind speed and sediment transport. This was done by two experiments that were carried out during the rainy seasons of 2002 and 2003 in north Burkina Faso, West Africa. Wind speeds were measured using three sonic anemometers, at a sampling frequency of 16 Hz. Sediment transport was determined by calculating the mass fluxes from 17 MWAC catchers. In this study, a shrub was defined as a vegetation element with branches until ground and a tree as a vegetation element with a distinctive trunk below a canopy.

Behind shrubs wind speed near the soil surface was reduced up to approximately seven times the height of the shrub. The observed reduction in wind speed in the area where wind speed was reduced was 15 per cent on average. At the sides of the shrub, wind speed was increased, by on average 6 per cent. As the area of increase in wind speed is one‐third of the area of decrease in wind speed, the net effect of a shrub is a reduction in wind speed. A similar pattern was visible for the pattern of sediment transport around a shrub. Downwind of a shrub, sediment transport was diminished up to seven times the height of the shrub. Probably most of this material was trapped by the shrub. Trees showed a local increase of wind around the trunk, which is expected to relate to an increase in sediment transport around the trunk. Mass flux measurements of sediment transport were not made, but visual observations in the field substantiate this. Behind the canopy of a tree, a tree acts similarly to a shrub regarding its effects on average wind speed, but as a tree is generally a larger obstacle than a shrub the extent of this effect is larger than for shrubs. Thus, whereas shrubs are more effective than trees regarding their direct effect on soil loss by trapping sand particles near the soil surface, trees are more effective in affecting soil loss indirectly by reducing the wind speed downwind more effectively than shrubs. Therefore, to reduce soil loss in an area, the presence of both trees and shrubs is crucial. Copyright © 2007 John Wiley & Sons, Ltd.
A historical view of imaging systems and technology
Authors: Robinson Enders A.
Published: March 2007

When approached from a historical viewpoint the development of many important imaging systems throughout history often share common ground. Extremely important was the development of the idea of mathematical projection which provides methods for making an image that conformally represents the object. The prime example is the discovery of the stereographic projection by Hipparchus of Nicaea in the second century BC. The stereographic projection provided the basis for the astrolabe, an astronomical device that acted both as an instrument of observation and as an analog computer. The stereographic projection and similar ones also provided the basis for the world maps of the ancients which utilized a grid of longitude and latitude. When the ancient Greek books were rediscovered in the Renaissance, the maps provided the impetus for the age of exploration. The Mercator projection of the sixteenth century was obtained as a logarithmic transformation of the stereographic projection. The Mercator projection provided sea captains with maps that had a rectangular grid of latitude and longitude and also had the property that straight lines represented courses of constant compass directions. The development of the telescope and microscope in the early seventeenth century provided means to obtain images that could not be seen by the unaided eye. Galileo's discovery of the moons of Jupiter led to Roemer's determination in 1676 that light travels at a finite velocity. Unknowingly, Roemer also discovered the relativistic Doppler effect, which in the present century helped to establish our concept of the expanding universe. The relativistic Doppler factor mathematically is none other than the expression for the stereographic projection of Hipparchus. The development of high energy physics in this century has led to images of the microworld of subatomic particles. In this environment Einstein's equation E = mc2 finds verification. This equation is a result of the theory of special relativity. The basic mathematics of special relativity is contained in the Lorentz transform. Again we can return to Hipparchus, because the Lorentz transform follows from a sequential application of the stereographic projection.
An iterative reconstruction algorithm for single photon emission computed tomography with cone beam geometry
Authors: Gullberg Grant T. , Zeng Gengsheng L. , Tsui Benjamin M. W. , Hagius John T.
Published: March 2007

An iterative EM reconstruction algorithm for single photon emission computed tomography is implemented for cone beam geometry that uses a ray‐driven projector‐backprojector. The cone beam projector‐backprojector models the attenuated Radon transform of a source distributed within an attenuator as line integrals of discrete voxels representing the source and attenuation distributions. The attenuation coefficient distribution for each voxel is assumed to be equal to the average value over a cubical region, and the integral of the source concentration through each voxel is obtained by interpolating between the source values at eight neighboring voxels. The calculation of the attenuation factors requires a specification of the attenuation distribution, estimated either from an assumed constant distribution with an estimated body outline or from transmission measurements. The distribution of attenuation coefficients is stored in memory, and the attenuation factors are calculated for each voxel during the projection and backprojection operations instead of using precalculated values. Computer simulations of half‐scan and full‐scan reconstructions show that the algorithm is able to compensate for attentuation and to suppress the propagation of artifacts that can result with limited angular sampling. The simulations verify that the algorithm has important application to cardiac SPECT imaging; because of variable attentuation through the thorax, it is necessary to use an iterative algorithm with an attenuation map in order to quantify radiopharmaceutical distributions in the heart.
Developments in high‐resolution positron emission tomography at MGH
Authors: Brownell G. L. , Burnham C. A. , Stearns C. W. , Chesler D. A. , Brownell A.‐L. , Palmer M. R.
Published: March 2007

The development of high resolution PET systems is important for the wider application of this techniques. The resolution of PET is limited by a number of physical factors such as positron range, small angle deviation, and sampling frequency. The design of the detector array and its sensitivity remain critical factors; designs incorporating analog coding have proven to be useful. PCR‐I, a single plane PET system, has demonstrated the concept and has produced useful images in animal studies. PCR‐II will extend the concept to a two dimensional detector array resulting in a system with high resolution and high sensitivity.
New examples of a recursive algorithm for calculating the echo pattern from a multilayered structure: Application to four‐layered structures
Authors: Lees Sidney
Published: March 2007

It was previously shown that the sonic echo wave pattern from a thin layer embedded between two thick layers can be readily and accurately calculated using a recursive expression (1). Two three‐layered experimental structures were described where the calculated and experimental wave patterns were successfully compared. It was shown that marked drastic changes in the echo wave pattern result from a layer much thinner than the pulse length.

The mathematical technique lends itself readily to computer calculation and can be employed in situations with an arbitrary number of layers. The power of the algorithm will be demonstrated here on a four‐layered structure. The material in the next section is taken directly from Ref. 1.
Estimating rigid‐body motion from three‐dimensional data without matching point correspondences
Authors: Lin Zse‐Cherng , Lee Hua , Huang Thomas S.
Published: March 2007

The estimation of the three‐dimensional (3‐D) motion parameters of a rigid body is a very important subject in scene analysis and trajectory prediction. Motion parameters can be estimated from two sets of object feature points before and after the motion. In general, the matching correspondences of the feature points are available, and the motion parameters can be estimated by solving equations associated with the correspondences. In this paper, we present a new method for motion estimation from 3‐D data without requiring the knowledge of matching correspondences.

In the noise‐free case, this approach identifies four candidates for the rotation matrix. The rotation matrix giving the best match of the point features can then be selected from the four candidates, and the matching correspondences are subsequently established. Possible ambiguities due to symmetrical feature points are also discussed in this paper. In the presence of noise, this method provides an initial estimate of the motion, which is then used to establish the matching correspondences. Subsequently, a new estimate of the motion parameters can be obtained with the established matching correspondence information. The effects of random zero‐mean noise are studied. Simulated results are shown to demonstrate the effectiveness and accuracy of this technique.
Inverse scattering, seismic traveltime tomography, and neural networks
Authors: Lu Shin‐Yee , Berryman James G.
Published: March 2007

Inverse scattering methods for reconstructing sound‐wave‐speed structure in the dimensions have been shown to be equivalent to inverting line integrals when the scattered field is of sufficiently high frequency and the scattering is sufficiently weak. Seismic traveltime tomography uses first arrival traveltime data to invert for wave‐speed structure. Of course, the traveltime is itself a line integral along a refracting ray path through the medium being probed. The similarity between these two inversion problems is discussed. One type of neural network‐the Hopfield net‐may be used to improve the traveltime inversion. We find that, by taking advantage of the general relationship between least‐squares solution and generalized inverses, the neural networks approach eliminates the need for inverting singular or poorly conditioned matrices and therefore also eliminates the need for the damping term often used to regularize such inversions. This procedure produces reconstructions with fewer artifacts and faster convergence than those attained previously using damped least‐squares methods.
Contour reconstruction in diffraction tomography
Authors: Ladas Kostas T. , Tsihrintzis George A.
Published: March 2007

We address the problem of reconstructing the directional derivative and/or the Laplacian of an object function f characterizing a weakly inhomogeneous scatterer directly from data collected in a set of scattering experiments. We employ the Rytov approximation to model the complex phase of the scattered wavefields and show that a minimum‐norm least‐squares solution can be obtained from the well known filtered backpropagation algorithm of diffraction tomography with appropriate modification of the tomographic filters employed in the filtering step of the algorithm. The procedure is illustrated by a computer simulation study.
Imaging of earthquake sources
Authors: Morales Jorge , McMechan George A.
Published: March 2007

Elastic waves, produced by temporally and spatially finite fault ruptures during earthquakes, propagate through the Earth. Recordings of these waves at the Earth's surface provide the data for reconstruction of the source properties, including location, spatial and temporal extents, and rupture velocities. A 2D finite‐difference solution of the elastic wave equation is used to numerically extrapolate synthetic observations backward in time to create images of the energy release during an earthquake.
Solid modeling of space stations in a concurrent processing environment
Authors: Saleh A. , Adeli H.
Published: March 2007

This article presents solid modeling of space station structures in a multiprocessing environment such as the Cray YMP 8/864. A space station is modeled as a collection of space trusses. Elements of trusses are created concurrently using constructive solid geometry. Concurrent solid modeling of large structures can be integrated with parallel algorithms for optimization of such structures in order to fully automate their computer‐aided design in a multiprocessing environment.
Planetary cameras
Authors: Anderson J. L. , Collins S. A. , Klaasen K. P. , Reilly T. H.
Published: March 2007

The “first look” phase of planetary imaging has been completed, with many spectacular discoveries made by a wide variety of cameras and spacecraft. Now that planetary scientists have a better idea about what is out there, new cameras can be developed to address specific questions in greater depth. Ideally, these cameras would be fully optimized to carry out their scientific objectives. In reality, however, the numerous constraints and severe environments of a planetary spacecraft often influence the camera design as strongly as the science. New developments in optics, detectors, microcomputers, and structural materials have greatly expanded the capabilities that can be built into a small, lightweight, low‐power instrument, and further progress is expected in the coming decade. The new camera designs will be used on a variety of flyby, orbiter, lander, and rover missions now in preparation by NASA and other space agencies throughout the world.
Design and development of the mars observer camera
Authors: Malin M. C. , Danielson G. E. , Ravine M. A. , Soulanille T. A.
Published: March 2007

The Mars Observer Camera (MOC) consists of three integrated optical subassemblies (one narrow‐angle and two wide‐angle cameras) with common electronics, designed to take high‐spatial‐resolution pictures of the surface of Mars and lower‐spatial‐resolution, synoptic coverage of the planet's surface and atmosphere. It incorporates several advanced technologies, including the use of graphite/epoxy structural materials, 32‐bit microprocessors, 108‐bit digital buffers, and high‐speed custom integrated circuits. The cameras use the “push broom” technique to build pictures, one line at a time, as the spacecraft orbits the planet. The narrow‐angle camera can acquire images of areas ranging from 2.9 × 2.9 km2 to 2.9 × 25.2 km2 at a resolution of 1.4 m/pixel. Additionally, lowerresolution pictures (to a lowest resolution of about 11 m/pixel) can be acquired through the narrow‐angle camera by pixel averaging; these images can be much longer (up to 2.9 × 500 km at 11 m/pixel). The wide‐angle cameras are capable of viewing Mars from horizon to horizon and, in a single 24‐hour period, can acquire a complete global image of the planet at a resolution of at least 7.5 km/pixel. Regional areas (covering hundreds of kilometers on a side) may be photographed at a resolution of better than 250 m/pixel at the nadir. The two wide‐angle cameras image through a different spectral filter, allowing the construction of color images. The MOC is a cylinder 88 cm in length and about 40 cm in diameter; the redundant electronics, equivalent in complexity and computational power to two engineering workstations, fit within a volume 40 cm in diameter and 10 cm long behind the narrow‐angle primary mirror. NASA's Mars Observer mission has adopted a distributed operations philosophy: all uplink and downlink activities for the MOC and the other payload experiments will occur remote from the Jet Propulsion Laboratory's command centers. Following its year‐long flight to Mars (launch is scheduled for 16 September 1992), Mars Observer is planned to acquire data for one Mars year (687 Earth days). During that time, MOC will acquire about 2 × 1012 bits of image and engineering data. During the last three months of the mission, Mars Observer will use a French‐supplied relay system to acquire an additional 2 × 109 bits of data from balloons deployed as part of the Soviet Mars '94 mission. These data will be collected and transferred to the Earth through the MOC electronics.
A multiangle imaging spectroradiometer for terrestrial remote sensing from the earth observing system
Authors: Diner David J. , Bruegge Carol J. , Martonchik John V. , Bothwell Graham W. , Danielson Eric D. , Floyd Elmer L. , Ford Virginia G. , Hovland Larry E. , Jones Kenneth L. , White Mary L.
Published: March 2007

The Multiangle Imaging SpectroRadiometer (MISR) instrument for the Earth Observing System (EOS) will provide a unique opportunity for studying the ecology and climate of the Earth through the acquisition of systematic, global multiangle imagery in reflected sunlight. MISR employs nine discrete cameras pointed at fixed angles, viewing the nadir direction and forward and aftward along the spacecraft ground track. Each camera is a charge‐coupled‐device –based pushbroom imager. Within a 7‐minute period, every point in a 204‐km‐wide swath is imaged at the nine viewing angles, ensuring observations acquired under virtually identical illumination and atmospheric conditions. The cameras will image the Earth in the nadir direction and at 30.7°, 45.6°, 60.0°, and 72.5° forward and aftward of the local vertical at the Earth's surface. Images at each angle will be obtained in four spectral bands centered at 440, 550, 670, and 860 nm. MISR is capable of taking image data in two different spatial resolution modes: Local Mode, in which selected targets are observed with 240‐m spatial sampling, and Global Mode, where the entire sunlit Earth is observed continuously with 1.92‐km sampling. Absolute radiometric calibration of the MISR instrument will be performed in‐flight using special on‐board hardware. The data produced by MISR will be valuable in a number of scientific discipline areas, and MISR images and geophysical products will be archived at the EOS Data and Information System to make them available to the broad scientific community.
Using image pyramids for the visualization of large terrain data sets
Authors: Stanfill Daniel F.
Published: March 2007

Viewing terrain data from various remote sensors in three dimensions has proven to be a valuable tool for scientists in understanding a variety of problems. A technique is presented for using image pyramids in such visualization of large terrain data sets, providing up to two orders of magnitude performance enhancement over simpler techniques, while at the same time eliminating false high‐frequency information, which causes animations to sparkle.
On the uniqueness of determination of a polyhedron by its edges with applications to the inverse potential problem
Authors: Brodsky M. A. , Strakhov V. N.
Published: March 2007

The uniqueness of determination of a polyhedron homeomorphic to a bali by its edge graph is proved in the most general situation. Consequences are given that arise from this result in the inverse potential problem. Unsolved problems are formulated.
Recent advances in scanning tomographic acoustic microscopy
Authors: Chiao Richard Y. , Lee Hua
Published: March 2007

We present the recent developments of the Scanning Tomographic Acoustic Microscope (STAM). The STAM was proposed as a method to achieve 3D imaging capability for the Scanning Laser Acoustic Microscope (SLAM). With the addition of a quadrature receiver, the complex scattered wave field can now be detected, and consequently the STAM is capable of subsurface holographic and tomographic imaging. The resolution improvement of the STAM can be attributed directly to the detection of the phase information and the image reconstruction technique. The STAM is sensitive to phase errors in the tomographic projections. In particular, the quadrature phase error and the initial phase error in the complex projections are critical to the tomographic reconstruction process. For multiple‐angle tomography, high‐precision projection registration and alignment become necessary. By obtaining solutions to these implementation problems, we have succeeded in obtaining images superior to the original SLAM images. In addition, quantitative ultrasonic imaging is possible with the STAM, and a method is presented to image the velocity parameter of simple specimens. With these capabilities, the STAM may become a useful tool for high‐resolution subsurface nondestructive evaluation.
Alternative approach to the shape from shading problem
Authors: Fain V. S.
Published: March 2007

The shape from shading procedure is not the only way to interpret the grey‐scale image of a surface independently on illumination conditions. An alternative approach is reported that considers a new surface as an unknown combination of fragments of know shapes, those shapes offering certain invariances to the illumination changeability.
Image analysis research and development in hungary
Authors: Chetverikov Dmitry , Álló Géza
Published: March 2007

We present a brief survey of recent Hungarian activities in digital image analysis, pattern recognition, and their application. Special attention in paid to the work done at Computer and Automation Institute (SzTAKI) and Computer Institute and Innovation Center (SzKI).
Construction of recognition decision rules in the class of logical functions
Authors: Lbov G. S.
Published: March 2007

We consider the class of logical decision rules of pattern recognition and introduce the concept of optimal rules from the given class. It is shown that the methods of construction of logical rules have a set of positive characteristics. A short description of program system LASTAN, which realizes the methods of data analysis, is given.