bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluations of Unformulated and FormulatedDendrimer-Based Microbicide Candidates in Mouse and Guinea PigModels of GenitalHerpes
Authors: Bernstein D. I. , Stanberry L. R. , Sacks S. , Ayisi N. K. , Gong Y. H. , Ireland J. , Mumper R. J. , Holan G. , Matthews B. , McCarthy T. , Bourne N.
Published: November 2003

Prevention
of sexually transmitted infections is a priority in developed and
developing countries. One approach to prevention is the use of topical
microbicides, and one promising approach is the use of dendrimers,
highly branched macromolecules synthesized from a polyfunctional core.
Three new dendrimer products developed to provide stable and
cost-efficient microbicides were initially evaluated in vitro for
anti-herpes simplex virus activity and then in vivo by using a mouse
model of genital herpes. From these experiments one product, SPL7013,
was chosen for further evaluation to define the dose and duration of
protection. Unformulated SPL7013 provided significant protection from
genital herpes disease and infection at concentrations as low as 1
mg/ml and for at least 1 h following topical (intravaginal)
administration of 10 mg/ml. This compound was then formulated into
three vehicles and further evaluated in mouse and guinea pig models of
genital herpes infection. In the murine evaluations each of the
formulations provided significant protection at concentrations of 10
and 50 mg/ml. Formulated compounds provided protection for at least
1 h at a concentration of 10 mg/ml. From these experiments
formulation 2V was chosen for dose ranging experiments using the guinea
pig model of genital herpes. The guinea pig evaluations suggested that
doses of 30 to 50 mg/ml were required for optimal protection. From
these studies a lead compound and formulation (2V of SPL7013) was
chosen for ongoing evaluations in primate models of simian
immunodeficiency virus and
Chlamydia trachomatis
infection.
aph(3′)-IIb
, a Gene Encoding anAminoglycoside-Modifying Enzyme, Is under the Positive Control ofSurrogate RegulatorHpaA
Authors: Zeng Lin , Jin Shouguang
Published: November 2003

Pseudomonas
aeruginosa
harbors a chromosomal aminoglycoside phosphotransferase
gene,
aph(3′)-IIb
, which confers
P.
aeruginosa
resistance to several important aminoglycoside
antibiotics, including kanamycin A and B, neomycin B and C, butirosin,
and seldomycin F5. The
aph(3′)-IIb
gene has been found
to be regulated by an AraC-type transcriptional regulator (HpaA)
encoded by a gene located upstream of the
aph(3′)-IIb
gene. In the presence of 4-hydroxyphenylacetic acid (4-HPA), HpaA
activates the expression of
aph(3′)-IIb
as well as
that of the
hpa
regulon which encodes metabolic enzymes for
the utilization of 4-HPA.
hpaA
and
aph(3′)-IIb
form an operon, and in response to the
presence of 4-HPA, the wild-type
P. aeruginosa
strain PAK (but
not its
hpaA
mutant strain) displays increased resistance to
neomycin. A survey of 39 clinical and 19 environmental isolates of
P. aeruginosa
demonstrated in all of them the presence of an
hpaA-aph
gene cluster, while 56 out of the 58 isolates are
able to utilize the 4-HPA as a sole carbon source, suggesting a feature
common to
P. aeruginosa
strains. Interestingly, a larger
portion of clinical isolates than environmental isolates showed
4-HPA-induced resistance to neomycin. The
aph(3′)-IIb
gene product is likely to function as a metabolic enzyme which has a
cross-reactivity with aminoglycosides. These findings provide new
insight into the possible mechanism of
P. aeruginosa
antibiotic
resistance.
Carbapenem-Resistant Strain of
Klebsiellaoxytoca
Harboring Carbapenem-Hydrolyzingβ-LactamaseKPC-2
Authors: Yigit Hesna , Queenan Anne Marie , Rasheed J. Kamile , Biddle James W. , Domenech-Sanchez Antonio , Alberti Sebastian , Bush Karen , Tenover Fred C.
Published: November 2003

We
investigated a
Klebsiella oxytoca
isolate demonstrating
resistance to imipenem, meropenem, extended-spectrum cephalosporins,
and aztreonam. The MICs of both imipenem and meropenem were 32μ
g/ml. The β-lactamase activity against imipenem and
meropenem was inhibited in the presence of clavulanic acid. Isoelectric
focusing studies demonstrated five β-lactamases with pIs of 8.2
(SHV-46), 6.7 (KPC-2), 6.5 (unknown), 6.4 (probable OXY-2), and 5.4
(TEM-1). The presence of the
bla
SHV
and
bla
TEM
genes was confirmed by specific PCR assays
and DNA sequence analysis. Transformation and conjugation studies with
Escherichia coli
showed that the β-lactamase with a pI
of 6.7,
Klebsiella pneumoniae
carbapenemase-2 (KPC-2), was
encoded on an approximately 70-kb conjugative plasmid that also carried
SHV-46, TEM-1, and the β-lactamase with a pI of 6.5. The
bla
KPC-2
determinant was cloned in
E. coli
and conferred resistance to imipenem, meropenem, extended-spectrum
cephalosporins, and aztreonam. The amino acid sequence of KPC-2 showed
a single amino acid difference, S174G, when compared with KPC-1,
another carbapenem-hydrolyzing β-lactamase from
K.
pneumoniae
1534. Hydrolysis studies showed that purified KPC-2
hydrolyzed not only carbapenems but also penicillins, cephalosporins,
and aztreonam. KPC-2 had the highest affinity for meropenem. The
kinetic studies revealed that KPC-2 was inhibited by clavulanic acid
and tazobactam. An examination of the outer membrane proteins of the
parent
K. oxytoca
strain demonstrated that it expressed
detectable levels of OmpK36 (the homolog of OmpC) and a
higher-molecular-weight OmpK35 (the homolog of OmpF). Thus, carbapenem
resistance in
K. oxytoca
3127 is due to production of the Bush
group 2f, class A, carbapenem-hydrolyzing β-lactamase KPC-2.
This β-lactamase is likely located on a transposon that is part
of a conjugative plasmid and thus has a very high potential for
dissemination.
ON THE COMPUTATIONAL POWER OF PHYSICAL INTERACTIONS: BOUNDS ON THE NUMBER OF TIME STEPS FOR SIMULATING ARBITRARY INTERACTION GRAPHS
Authors: JANZING DOMINIK , WOCJAN PAWEL , BETH THOMAS
Published: November 2003

The most popular model of quantum computation is the quantum circuit model using single and two qubit gates as elementary transformations. Definitions of quantum complexity usually refer to this model. In contrast, we consider the physical interactions among the qubits as the basic computational resource that allows to carry out complex transformations on the quantum register. One method to compare the computational power of different interactions is to examine the complexity of the so-called mutual simulation of interaction Hamiltonians. The physical interaction can simulate other interactions by interspersing the natural time evolution with external control operations. In previous papers we have considered mutual simulation of n-partite pair-interaction Hamiltonians. We have focussed on the running time overhead of general simulations, while considering the required number of time steps only for special cases (decoupling and time-reversal). These two complexity measures differ significantly. Here we derive lower bounds on the number of time steps for simulations of general interaction graphs. In particular, the simulation of interaction graphs with irrational spectrum requires at least n steps. We discuss as examples graphs that correspond to graph codes and nearest neighbor interactions in 1- and 2-dimensional lattices. In the latter case the lower bounds are almost tight.
A ROBUST SUBSPACE ALGORITHM FOR PRINCIPAL COMPONENT ANALYSIS
Authors: WEINGESSEL ANDREAS , HORNIK KURT
Published: November 2003

We present a noise robust PCA algorithm which is an extension of the Oja subspace algorithm and allows tuning the noise sensitivity. We derive a loss function which is minimized by this algorithm and interpret it in a noisy PCA setting. Results on the local stability analysis of this algorithm are given and it is shown that the locally stable equilibria are those which minimize the loss function.
THE NONLINEAR PREDICTABILITY OF THE ELECTROTELLURIC FIELD VARIATIONS DATA ANALYZED WITH SUPPORT VECTOR MACHINES AS AN EARTHQUAKE PRECURSOR
Authors: IFANTIS A. , PAPADIMITRIOU S.
Published: November 2003

This work investigates the nonlinear predictability of the Electro Telluric Field (ETF) variations data in order to develop new intelligent tools for the difficult task of earthquake prediction. Support Vector Machines trained on a signal window have been used to predict the next sample. We observe a significant increase at this short-term unpredictability of the ETF signal at about two weeks time period before the major earthquakes that took place in regions near the recording devices. The unpredictability increase can be attributed to a quick time variation of the dynamics that produce the ETF signal due to the earthquake generation process. Thus, this increase can be taken into advantage for signaling for an increased possibility of a large earthquake within the next few days in the neighboring region of the recording station.
Heterogeneity of Chinese Medical Herbs in Singapore Assessed by Fluorescence AFLP Analysis
Authors: Yuan Meifang , Hong Yan
Published: November 2003

There are conflicting records on the identity of Chinese medical herbs, and it is known that different plant materials are used under the same common names in different regions in China. However, there is no study on the genetic heterogeneity of medical herbs in any market outside of China. In this report, Chinese medical herbs under common names Radix Quinquefolii (American Ginseng or Xiyangshen), Radix Astragali (Huangqi), Radix Notoginseng (Tianqi), Coxtex Cinnamomum (Guipi), Radix Isatidis (Banlangen), Radix Codonopsis (Dangshen) and Radix Rehmannia (Shengdi) were collected from three independent herbal shops in Singapore and their DNAs were isolated and subjected to fluorescence Amplified Fragment Length Polymorphism (AFLP) analysis. While samples for Radix Quinquefolii and Radix Astragali were homogenous genetically [similarity index (SI) = 0.85 – 1.00] across the three shops, genetic heterogeneity was found for the other herbs (SI < 0.7). For example, four samples of Radix Codonopsis were of three distinct patterns (SI < 0.6). Our results highlight the situation that genetically distinct herbal materials are labeled and marketed under the same common names in an international market of Chinese medical herbs, which may contribute to inconsistency in quality and efficacy.
The Pain-Relieving Effects Induced by Electroacupuncture with Different Intensities at Homotopic and Heterotopic Acupoints in Humans
Authors: Xu Wei-Dong , Zhu Bing , Rong Pei-Jing , Bei Hui , Gao Xin-Yan , Li Yu-Qing
Published: November 2003

The purpose of the present study was to investigate the relationship between the distribution of the analgesic area when different intensities of stimulation were applied to homotopic and heterotopic acupoints. The experiments were performed on volunteers; the left sural nerve was stimulated by a volley of eight rectangular pulses delivered at a frequency of 400 Hz. Electromyographic reflex responses (EMGs) were recorded from the ipsi-lateral biceps femoris muscle. Electroacupuncture stimuli were given on the skin overlying the Zusanli point (St 36), and the strengths chosen were times of the threshold eliciting a nociceptive reflex (TRIII) response (0.6, 0.8, 1.0, TRIII and Tsupra-RIII , respectively). The effects of homotopic and heterotopic stimuli applied to St 36 on the pain sensation and the RIII reflex elicited by stimulation of the left sural nerve were observed to explore the pain-relief and RIII reflex-inhibition produced by stimulation of the St 36 point with different intensities. Both the nociceptive reflex and painful sensation evoked by stimulating the sural nerve were similarly inhibited by electroacupuncture at less than TRIII applied to the ipsi-lateral acupoint. In other words, acupuncture with an innocuous intensity can produce homotopic pain-alleviating effects and reflex suppression. With contra-lateral electroacupuncture at the St 36 acupoint, innocuous intensities cannot produce heterotopic pain-relieving effects; these inhibitions were only observed at electroacupuncture intensities similar to the TRIII threshold. These results suggest that local acupuncture-induced analgesia is effective with activation of large afferent fibers, whereas heterotopic acupuncture-induced analgesia is only effective with intensities strong enough to excite small afferent fibers. Local analgesic effects of acupoint stimulation involve segmental inhibition, whereas systemic analgesic effects of acupoint stimulation are involved in contra-lateral effects. The latter may recruit the diffuse noxious inhibitory controls (DNIC) system. The specific function of an acupoint is determined by the anatomical relationship between the disease focus and the segmental location of the acupoint.
STANDARD MODEL CP VIOLATION IN B → Xdℓ+ℓ- DECAYS
Authors: EYGI ZEYNEP DENIZ , TURAN GÜRSEVIL
Published: November 2003

We investigate the CP violating asymmetry, the forward backward asymmetry and the CP violating asymmetry in the forward–backward asymmetry for the inclusive B → Xdℓ+ℓ- decays for the ℓ = e,μ,τ channels in the standard model. It is observed that these asymmetries are quite sizeable and B → Xdℓ+ℓ- decays seem promising for investigating CP violation.
THE ROLE OF ISOVECTOR MESON EXCHANGES TO NUCLEON–NUCLEON ELASTIC CROSS-SECTION
Authors: LI QINGFENG , ZHAO ENGUANG
Published: November 2003

The contributions of δ-isovector-scalar and ρ-isovector-vector meson-exchanges to nucleon–nucleon elastic cross-sections (ECS) are studied based on QHD-type effective Lagrangian within the framework of the RBUU transport theory. The detailed expressions of ECS for symmetric nuclear system have also obtained. The medium correction of ρ-meson mass and a proper symmetry energy coefficient are selected in order to fix a set of suitable coupling constants for δ and ρ exchanges with the constraint of free ECS as a function of energy. The respective δ and ρ contributions to free ECS as a function of energy are also shown and it is found they both affect the neutron–proton and neutron–neutron (proton–proton) ECS on the contrary way.
QUANTIZATION ON A TORUS WITHOUT POSITION OPERATORS
Authors: TANIMURA SHOGO
Published: November 2003

We formulate quantum mechanics in the two-dimensional torus without using position operators. We define an algebra with only momentum operators and shift operators and construct an irreducible representation of the algebra. We show that it realizes quantum mechanics of a charged particle in a uniform magnetic field and prove that any irreducible representation of the algebra is unitarily equivalent to each other. This work provides a firm foundation for the noncommutative torus theory.
THE COULOMB INTERACTION AND THE INVERSE FADDEEV–POPOV OPERATOR IN QCD
Authors: HALLER KURT , REN HAI-CANG
Published: November 2003

We give a proof of a local relation between the inverse Faddeev–Popov operator and the non-Abelian Coulomb interaction between color charges.
SOLAR MODELS: AN HISTORICAL OVERVIEW
Authors: BAHCALL JOHN N.
Published: November 2003

I will summarize in four slides the 40 years of development of the standard solar model that is used to predict solar neutrino fluxes and then describe the current uncertainties in the predictions. I will dispel the misconception that the p-p neutrino flux is determined by the solar luminosity and present a related formula that gives, in terms of the p-p and 7 Be neutrino fluxes, the ratio of the rates of the two primary ways of terminating the p-p fusion chain. I will also attempt to explain why it took so long, about three and a half decades, to reach a consensus view that new physics is being learned from solar neutrino experiments. Finally, I close with a personal confession and some personal remarks.
STATUS OF BOREXINO
Authors:   On behalf of the Borexino collaboration., IANNI ALDO
Published: November 2003

Borexino is a real-time solar neutrino detector under commissioning at the Gran Sasso underground laboratories (Italy). The main goal of the experiment is the spectroscopy of sub-MeV solar neutrinos focusing on the measurement of the 7 Be neutrino flux on Earth. In order to achieve such a goal Borexino has developed a new technology for large-scale low-count rate experiments. This paper reviews the status of the experiment and the strategy adopted to reach a high level of radiopurity. Besides its primary task Borexino will also be able to search for SuperNova neutrinos, non-standard neutrinos properties and neutrino from the Earth.
SO (10) GUT MODELS AND THEIR PRESENT SUCCESS IN EXPLAINING MASS AND MIXING DATA
Authors: ALBRIGHT CARL H.
Published: November 2003

Some features of SO(10) GUT models are reviewed, and a number of such models in the literature are compared. While some have been eliminated by recent neutrino data, others are presently successful in explaining the quark and lepton mass and mixing data. A short description of one very predictive model is given which illustrates some of the features discussed. Future tests of the models are pointed out including one which contrasts sharply with those models based on an Le - Lν - Lτ type symmetry.
OVERVIEW OF SUSY GUT MODELS OF NEUTRINO MIXING
Authors: BARR S.M.
Published: November 2003

A brief review is given of some ideas for explaining neutrino masses and mixings within the context of supersymmetric grand unification. Emphasis is put on so-called lopsided models.
Molecular Diagnostics
Authors: Braziel Rita M. , Shipp Margaret A. , Feldman Andrew L. , Espina Virginia , Winters Mary , Jaffe Elaine S. , Petricoin Emanuel F. , Liotta Lance A.
Published: November 2003

It is increasingly evident that molecular diagnostics, that is, the use of diagnostic testing to understand the molecular mechanisms of an individual patient’s disease, will be pivotal in the delivery of safe and effective therapy for many diseases in the future. A huge body of new information on the genetic, genomic and proteomic profiles of different hematopoietic diseases is accumulating. This chapter focuses on new technologies and advancements in understanding the molecular basis of hematologic disorders, providing an overview of new information and its significance to patient care.

In Section I, Dr. Braziel discusses the impact of new genetic information and research technologies on the actual practice of diagnostic molecular hematopathology. Recent and projected changes in methodologies and analytical strategies used by clinical molecular diagnostics laboratories for the evaluation of hematologic disorders will be discussed, and some of the challenges to clinical implementation of new molecular information and techniques will be highlighted.

In Section II, Dr. Shipp provides an update on current scientific knowledge in the genomic profiling of malignant lymphomas, and describes some of the technical aspects of gene expression profiling. Analysis methods and the actual and potential clinical and therapeutic applications of information obtained from genomic profiling of malignant lymphomas are discussed.

In Section III, Dr. Liotta presents an update on proteomic analysis, a new and very active area of research in hematopoietic malignancies. He describes new technologies for rapid identification of different important proteins and protein networks, and the potential therapeutic and prognostic value of the elucidation of these proteins and protein pathways in the clinical care of patients with malignant lymphomas.
Intravenous immune globulin prevents venular vaso-occlusion in sickle cell mice by inhibiting leukocyte adhesion and the interactions between sickle erythrocytes and adherent leukocytes
Authors: Turhan Aslihan , Jenab Pegah , Bruhns Pierre , Ravetch Jeffrey V. , Coller Barry S. , Frenette Paul S.
Published: November 2003

Sickle cell vaso-occlusion is a complex multistep process likely involving heterotypic interactions among sickle erythrocytes (red blood cells [RBCs]), leukocytes (white blood cells [WBCs]), and endothelial cells. Recent data using intravital microscopy in a sickle cell mouse model suggest that adherent leukocytes in postcapillary venules play a critical role in vaso-occlusion by capturing circulating sickle RBCs. In the course of studies to investigate the adhesion receptors mediating sickle RBC-WBC interactions, we found that control nonspecific immunoglobulin G (IgG) preparations displayed significant inhibitory activity. As a result, we studied the effects of commercial intravenous human immune globulin (IVIG) preparations and found that IVIG inhibits RBC-WBC interactions in cremasteric venules in a dose-dependent manner. IVIG of at least 200 mg/kg dramatically reduced these interactions, even after tumor necrosis factor-α (TNF-α) stimulation, and not only increased microcirculatory blood flow but also improved survival of sickle cell mice. These data raise the possibility that IVIG may have a beneficial effect on sickle cell–associated vaso-occlusion.
Remifentanil versus fentanyl for analgesia based sedation to provide patient comfort in the intensive care unit: a randomized, double-blind controlled trial [ISRCTN43755713]
Authors: Muellejans Bernd , López Angel , Cross Michael H , Bonome César , Morrison Lachlan , Kirkham Andrew JT
Published: November 2003

Introduction

This double-blind, randomized, multicentre study was conducted to compare the efficacy and safety of remifentanil and fentanyl for intensive care unit (ICU) sedation and analgesia.

Methods

Intubated cardiac, general postsurgical or medical patients (aged ≥ 18 years), who were mechanically ventilated for 12–72 hours, received remifentanil (9 μg/kg per hour; n = 77) or fentanyl (1.5 μg/kg per hour; n = 75). Initial opioid titration was supplemented with propofol (0.5 mg/kg per hour), if required, to achieve optimal sedation (i.e. a Sedation–Agitation Scale score of 4).

Results

The mean percentages of time in optimal sedation were 88.3% for remifentanil and 89.3% for fentanyl (not significant). Patients with a Sedation–Agitation Scale score of 4 exhibited significantly less between-patient variability in optimal sedation on remifentanil (variance ratio of fentanyl to remifentanil 1.84; P = 0.009). Of patients who received fentanyl 40% required propofol, as compared with 35% of those who received remifentanil (median total doses 683 mg and 378 mg, respectively; P = 0.065). Recovery was rapid (median time to extubation: 1.1 hours for remifentanil and 1.3 hours for fentanyl; not significant). Remifentanil patients who experienced pain did so for significantly longer during extubation (6.5% of the time versus 1.4%; P = 0.013), postextubation (10.2% versus 3.6%; P = 0.001) and post-treatment (13.5% versus 5.1%; P = 0.001), but they exhibited similar haemodynamic stability with no significant differences in adverse event incidence.

Conclusion

Analgesia based sedation with remifentanil titrated to response provided effective sedation and rapid extubation without the need for propofol in most patients. Fentanyl was similar, probably because the dosing algorithm demanded frequent monitoring and adjustment, thereby preventing over-sedation. Rapid offset of analgesia with remifentanil resulted in a greater incidence of pain, highlighting the need for proactive pain management when transitioning to longer acting analgesics, which is difficult within a double-blind study but would be quite possible under normal circumstances.
Offset of pharmacodynamic effects and safety of remifentanil in intensive care unit patients with various degrees of renal impairment
Authors: Breen Des , Wilmer Alexander , Bodenham Andrew , Bach Vagn , Bonde Jan , Kessler Paul , Albrecht Sven , Shaikh Soraya
Published: November 2003

Introduction

This open label, multicentre study was conducted to assess the times to offset of the pharmacodynamic effects and the safety of remifentanil in patients with varying degrees of renal impairment requiring intensive care.

Methods

A total of 40 patients, who were aged 18 years or older and had normal/mildly impaired renal function (estimated creatinine clearance ≥ 50 ml/min; n = 10) or moderate/severe renal impairment (estimated creatinine clearance <50 ml/min; n = 30), were entered into the study. Remifentanil was infused for up to 72 hours (initial rate 6–9 μg/kg per hour), with propofol administered if required, to achieve a target Sedation–Agitation Scale score of 2–4, with no or mild pain.

Results

There was no evidence of increased offset time with increased duration of exposure to remifentanil in either group. The time to offset of the effects of remifentanil (at 8, 24, 48 and 72 hours during scheduled down-titrations of the infusion) were more variable and were statistically significantly longer in the moderate/severe group than in the normal/mild group at 24 hours and 72 hours. These observed differences were not clinically significant (the difference in mean offset at 72 hours was only 16.5 min). Propofol consumption was lower with the remifentanil based technique than with hypnotic based sedative techniques. There were no statistically significant differences between the renal function groups in the incidence of adverse events, and no deaths were attributable to remifentanil use.

Conclusion

Remifentanil was well tolerated, and the offset of pharmacodynamic effects was not prolonged either as a result of renal dysfunction or prolonged infusion up to 72 hours.
Integrated prestack depth migration of vertical seismic profile and surface seismic data from the Rocky Mountain Foothills of southern Alberta, Canada
Authors: Grech M. Graziella Kirtland , Lawton Don C. , Cheadle Scott
Published: November 2003

We have developed an anisotropic prestack depth migration code that can migrate either vertical seismic profile (VSP) or surface seismic data. We use this migration code in a new method for integrated VSP and surface seismic depth imaging. Instead of splicing the VSP image into the section derived from surface seismic data, we use the same migration algorithm and a single velocity model to migrate both data sets to a common output grid. We then scale and sum the two images to yield one integrated depth‐migrated section. After testing this method on synthetic surface seismic and VSP data, we applied it to field data from a 2D surface seismic line and a multioffset VSP from the Rocky Mountain Foothills of southern Alberta, Canada. Our results show that the resulting integrated image exhibits significant improvement over that obtained from (a) the migration of either data set alone or (b) the conventional splicing approach. The integrated image uses the broader frequency bandwidth of the VSP data to provide higher vertical resolution than the migration of the surface seismic data. The integrated image also shows enhanced structural detail, since no part of the surface seismic section is eliminated, and good event continuity through the use of a single migration–velocity model, obtained by an integrated interpretation of borehole and surface seismic data. This enhanced migrated image enabled us to perform a more robust interpretation with good well ties.
Efficient acquisition, processing, and interpretation strategy for shallow 3D seismic surveying: A Case Study
Authors: Spitzer Roman , Nitsche Frank O. , Green Alan G. , Horstmeyer Heinrich
Published: November 2003

A new 3D seismic reflection data set has been used to map the shallow subsurface beneath a key region of the Swiss Rhine Valley. Seismic signals generated by a pipegun were recorded with single 30‐Hz geophones distributed across a 277.5 × 357.0‐m area. The dense distribution of sources and receivers resulted in a binning grid of 2.12 × 2.12 m and an average fold of ∼22. To improve the visibility and continuity of reflections, a novel processing strategy was designed and applied to the acquired data. A combination of regridding and sharing traces in the common midpoint (CMP) domain resulted in increased S/N ratios with only minor loss of resolution. This prestack interpolation method yielded composite CMPs distributed on a 1.5 × 1.5‐m binning grid and an increased average fold of ∼44. The composite CMPs were subjected to a combined linear and hyperbolic τ–p processing scheme that led to the effective separation of reflections from source‐generated noise. Finally, 3D depth migration of the stacked data produced high‐resolution images of the subsurface from ∼15 to ∼130 m depth. On the basis of characteristic seismic facies and information from nearby boreholes, four principal lithological units were identified. At increasing depths they were glaciofluvial sand and gravel, glaciolacustrine clay and silt, morainal deposits, and sandstone basement. These lithological units were separated by three principal reflecting boundaries that were mapped through the data volume using semiautomatic tracking procedures. The deepest boundary defined a trough‐shaped basement structure.
Velocity‐porosity relationships, 1: Accurate velocity model for clean consolidated sandstones
Authors: Knackstedt Mark A. , Arns Christoph H. , Pinczewski W. Val
Published: November 2003

We use numerical simulations to derive the elastic properties of model monomineralic consolidated sandstones. The model morphology is based on overlapping spheres of a mineral phase. We consider model quartzose and feldspathic sands. We generate moduli‐porosity relationships for both the dry and water‐saturated states. The ability to control pore space structure and mineralogy results in numerical data sets which exhibit much less noise than corresponding experimental data. The numerical data allows us to quantitatively analyze the effects of porosity and the properties of the mineral phase on the elastic properties of porous rocks. The agreement between the numerical results and available experimental data for clean consolidated sandstones is encouraging.

We compare our numerical data to commonly used theoretical and empirical moduli‐porosity relationships. The self‐consistent method gives the best theoretical fit to the numerical data. We find that the empirical relationship of Krief et al. is successful at describing the numerical data for dry shear modulus and that the recent empirical method of Arns et al. gives a good match to the numerical data for Poisson's ratio or Vp/Vsratio of dry rock. The Raymer equation is the best of the velocity‐porosity models for the water‐saturated systems. Gassmann's relations are shown to accurately map between the dry and fluid‐saturated states.

Based on these results, we propose a new empirical method, based solely on a knowledge of the mineral modulus, to estimate the full velocity‐porosity relationship for monomineralic consolidated sands under dry and fluid‐saturated states. The method uses the equation of Krief et al. for the dry shear modulus and the empirical equation of Arns et al. for the dry Poisson's ratio. Gassmann's relations are applied to obtain the fluid‐saturated states. The agreement between the new empirical method, the numerical data and available experimental data for dry and water‐saturated states is encouraging.
Determination of thermal properties and formation temperature from borehole thermal recovery data
Authors: Lee Tien‐Chang , Duchkov A. D. , Morozov S. G.
Published: November 2003

Thermal recovery in boreholes cooled by circulation of drilling mud has been modeled for estimating formation temperature and thermal conductivity. Coupled with a finite‐element simulation of heat conduction, inverse modeling for the desired parameters starts with a genetic algorithm that feeds initial estimates of model parameters to an iterative quasi‐linear inversion scheme. In addition to using the rms misfit between the computed and observed borehole temperatures, the results are assessed by comparing or constraining the model formation temperature with a value obtained conventionally from an asymptotic temperature–time relation for a steady line source. The model conductivity is further evaluated for equality with a conductivity value, which is estimated through simulation of heat exchange between the formation and circulating mud. Test results on synthetic data and two sets of highly noisy borehole data from Lake Baikal in Russia indicate that the two equality criteria in temperature and conductivity are achievable. Multiple runs of GA‐IM are used to find mean parameter values and their uncertainties. The resultant model conductivity values are consistent with those measured in cores with a needle‐probe method.
Predicting seismic velocity and other rock properties from clay content only
Authors: Pratson Lincoln F. , Stroujkova Anastasia , Herrick Damian , Boadu Fred , Malin Peter
Published: November 2003

It has been shown that accurate predictions of compressional and shear‐wave velocities can be derived from measurements of clay content, porosity, and bulk density. In this paper, we test the efficacy of using a sequence of established petrophysical formulations to go a step further and predict porosity and bulk density as well as velocity from clay content alone. Other variables, like grain and pore‐fluid properties, are assumed to be constant, while empirical relationships are used to model such behaviors as grain packing and compaction.

The sequence of formulations, referred to as the “model,” is evaluated using well‐log and core data from the Amazon Fan collected during Ocean Drilling Program Leg 155. Clay contents are estimated from the borehole gamma‐ray logs. These are input to the model, which in turn predicts observed porosities to a rms error of <20%, and bulk densities and compressional velocities to rms errors of ≤10%. The results suggest that with better measurements of clay content and improvements to the model, even more accurate predictions of velocity might be achieved for unconsolidated sediments.
Simultaneous 1D inversion of loop–loop electromagnetic data for magnetic susceptibility and electrical conductivity
Authors: Farquharson Colin G. , Oldenburg Douglas W. , Routh Partha S.
Published: November 2003

Magnetic susceptibility affects electromagnetic (EM) loop–loop observations in ways that cannot be replicated by conductive, nonsusceptible earth models. The most distinctive effects are negative in‐phase values at low frequencies. Inverting data contaminated by susceptibility effects for conductivity alone can give misleading models: the observations strongly influenced by susceptibility will be underfit, and those less strongly influenced will be overfit to compensate, leading to artifacts in the model. Simultaneous inversion for both conductivity and susceptibility enables reliable conductivity models to be constructed and can give useful information about the distribution of susceptibility in the earth. Such information complements that obtained from the inversion of static magnetic data because EM measurements are insensitive to remanent magnetization.

We present an algorithm that simultaneously inverts susceptibility‐affected data for 1D conductivity and susceptibility models. The solution is obtained by minimizing an objective function comprised of a sum‐of‐squares measure of data misfit and sum‐of‐squares measures of the amounts of structure in the conductivity and susceptibility models. Positivity of the susceptibilities is enforced by including a logarithmic barrier term in the objective function. The trade‐off parameter is automatically estimated using the generalized cross validation (GCV) criterion. This enables an appropriate fit to the observations to be achieved even if good noise estimates are not available. As well as synthetic examples, we show the results of inverting airborne data sets from Australia and Heath Steele Stratmat, New Brunswick.
Automated anomaly picking from broadband electromagnetic data in an unexploded ordnance (UXO) survey
Authors: Huang Hoaping , Won I. J.
Published: November 2003

We present automated anomaly‐picking methods for detecting unexploded ordnance (UXO) from broadband electromagnetic (EM) data. Using data consisting of in‐phase and quadrature responses at multiple (typically 10) frequencies, a detector function attempts to detect all metal objects but to suppress false alarms caused by geology, variations in sensor height, and sensor motions in the earth's magnetic field.

Promising detector functions considered here are (1) the sum of all quadrature responses, Qsum, (2) the sum of all differences among the in‐phase or quadrature components, Ispreador Qspread, (3) the sum of the Ispreadand Qspreads, Tspread, (4) the weighted total apparent conductivity (TAC) from all frequencies, and (5) the apparent magnetic susceptibility (AMS) derived from the lowest frequency of a survey. These detector functions favor metallic objects and are relatively insensitive to geologic variations and motion‐induced noise, which are common with a handheld or cart‐mounted sensor in rough terrain. We discuss the properties of these detector functions, apply them to field data from two sites, and compare the results with limited ground truths. Based on the theoretic study and test on the real data, the total apparent conductivity is the best detector function for picking and classifying anomalies, which shows more distinct anomalies and quieter background than other detector functions.
3D resistivity mapping of airborne EM data
Authors: Zhang Zhiyi
Published: November 2003

A 3D resistivity mapping technique has been developed to provide fast estimates of resistivity distributions in airborne electromagnetic surveys. This proposed 3D mapping method consists of an approximate 3D linear inverse operator and a generalized subspace solver. The 3D inverse operator can be generated using any forward approximation that is linear in resistivity. The generalized subspace method is an alternative to the conjugate gradient method, and it reduces the original large linear system of equations to a much smaller but nonlinear one that is solved iteratively. The major benefit of using generalized subspace methods is that subspace vectors can be built based upon physical principles such as skin and investigation depths. Since the 3D mapping is a linear inverse problem, no iteration, and thus no forward modeling nor sensitivity updating, is needed. The 3D resistivity‐mapping technique can be used directly to estimate 3D resistivity distribution or to provide a model update during an intermediate iteration in a nonlinear 3D inversion. Synthetic and field data examples indicate that the 3D mapping can provide quantitative information about the resistivity and spatial distributions of the 3D targets.
2D modeling and inversion of gravity data using density contrast varying with depth and source–basement geometry described by the Fourier series
Authors: García‐Abdeslem Juan
Published: November 2003

A method is developed for 2D forward modeling and nonlinear inversion of gravity data. The forward modeling calculates the gravity anomaly caused by a 2D source body with an assumed depth‐dependent density contrast given by a cubic polynomial. The source body is bounded at depth by a smooth, curvilinear surface given by the Fourier series, which represents the basement. The weighted and damped discrete nonlinear inverse method presented here can invert gravity data to infer the geometry of the source body. The use of the Fourier series to define the basement geometry allows the interpreter to reconstruct a broad variety of geometries for the geologic structures using a small number of free parameters. Both modeling and inversion methods are illustrated with examples using field gravity data across the San Jacinto graben in southern California and across the Sayula basin in Jalisco, Mexico.

The inversion of the San Jacinto graben residual Bouguer gravity data yields results compatible with those from previous interpretations of the same data set, suggesting that this geologic structure accommodates about 2.5 km of sediments. The inversion of the residual Bouguer gravity data across the Sayula basin suggests a maximum of 1‐km‐thick sedimentary infill.
A new method for continuation of 3D potential fields to a horizontal plane
Authors: Xu Shi‐zhe , Yang Chieh‐Hou , Dai Shikun , Zhang Dahai
Published: November 2003

A 3D potential on a 3D topography is approximately regarded as a potential on an imaginary horizontal plane. A fast Fourier transform (FFT) is applied to calculate the outward normal derivative of the potential on the horizontal plane. An approximation can be made such that the calculated derivative is used as the outward normal derivative of the potential on the 3D topographic surface. Based on the potential and the approximated normal derivative on the topography, Green's formula is used to obtain the potential at an arbitrary point above the topography. When the potential at a flat level above the topography is obtained, an FFT is used again to determine the potential at other levels above the source of the potential.

A model test shows that the results from this method compare well with analytic solutions. The method has high computation speed and can be used for continuation of 3D potential fields for large data sets, e.g., aeromagnetic data.
Propagation of a ground‐penetrating radar (GPR) pulse in a thin‐surface waveguide
Authors: Arcone Steven A. , Peapples Paige R. , Liu Lanbo
Published: November 2003

Field observations are tested against modal propagation theory to find the practical limitations upon derivation of layer permittivities and signal attenuation rates from a radar moveout profile over two‐layer ground. A 65‐MHz GPR pulse was transmitted into a 30‐60‐cm‐thick surface waveguide of wet, organic silty to gravelly soil overlying a drier refracting layer of sand and gravel. Reflection profiles, trench stratigraphy, resistivity measurements, and sediment analysis were used to quantify the propagation medium and possible attenuation mechanisms.

Highly dispersive modal propagation occurred within the waveguide through 35 m of observation. The fastest phase velocity occurred at the waveguide cutoff frequency of 30 MHz, which was well received by 100‐MHz antennas. This speed provides the refractive index of the lower layer, so the near‐cutoff frequencies must match a lower layer refraction. A slower, lower frequency phase of the dispersed pulse occurred at about 60–70 MHz, with an average attenuation rate of about 0.4 dB/m. Similar events appear to have reflected back and forth along the waveguide. Modal theory for the average layer thickness shows all primary events to be different aspects of a TE1 mode, predicts the correct 30–70‐MHz phase speeds and low‐frequency cutoff phenomenon, but also predicts that the 60–70‐MHz group speed should be slightly lower than observed. An Airy phase was apparently out of the bandwidth. Two‐dimensional finite‐difference time‐domain modeling qualitatively simulates the main field results.

After accounting for an inverse dependency of amplitude on the square of the range, the high resistivity of the surface layer accounts for the 0.4‐dB/m attenuation rate for the 60–70‐MHz phase of the pulse. However, erratic amplitudes, interface roughness, and the reflected packets indicate scattering. We conclude that permittivities can be well estimated from dispersive moveout profiles given an average surface layer thickness, and the wide bandwidth of GPR antennas allows the full dispersion to be seen. Attenuation rates appear to be derivable from the higher frequency part of our dispersive event, for which attenuation might be least affected by the waveguide dispersion.
Effects of fractal fluctuations in topographic relief, permittivity and conductivity on ground‐penetrating radar antenna radiation
Authors: Lampe Bernhard , Holliger Klaus
Published: November 2003

Typical ground‐penetrating radar (GPR) transmitters and receivers are dipole antennas. These antennas have pronounced directivity properties and exhibit strong coupling to interfaces across which there are changes in electric material properties. Antenna coupling to the surface of idealized half‐space models has been the subject of intense research for several decades. In contrast, the behavior of antennas in the vicinity of interfaces with realistic topographic fluctuations and/or subsurface heterogeneities has been largely unexplored. To explore this issue, we simulate the responses of a typical surface GPR antenna system located on a suite of realistic fractal earth models using the finite‐difference time‐domain (FDTD) method. The models are characterized by topographic roughness of the air–soil interface and small‐scale heterogeneous distributions of permittivity and conductivity in the subsurface. Synthetic radiation patterns and input impedance values of the simulated GPR antenna system demonstrate that topographic roughness significantly affects the coupling of the antenna to the ground, whereas heterogeneities in the subsurface predominantly influence the antenna radiation through scattering and absorption along the propagation path.
Differential reduction of magnetic anomalies to the pole on a massively parallel computer
Authors: Lu Richard S. , Mariano John , Willen Dennis E.
Published: November 2003

A finite‐impulse‐response filter was implemented on a computer with massively parallel processors to reduce a magnetic anomaly map to the magnetic pole, allowing each grid node to have a different inclination and declination (differential reduction to the pole, DRTP). The dramatic speed improvement of such an implementation for the filter design and application via space‐domain convolution makes DRTP a practical tool for hydrocarbon and mineral exploration.

Application of this tool to magnetic anomalies in east China reveals that the northward shift in position of the anomaly maximum generated by DRTP is 6 km for anomalies with dominant wavelengths of approximately 25 km in the northernmost part of the study area. The shift increases as the anomaly wavelength increases. Shifts for all anomaly wavelengths are even larger in the southern part of the study area, where the magnetic inclination is lower. The shift in position of the anomaly maximum for anomalies of wavelengths 25 km in the northernmost area produced by DRTP is 2 km less than that produced by a conventional reduction to the pole using the inclination and declination at the central location of the study area. Once again, such differences in shifts are larger for anomalies of longer wavelengths. The farther away from the central location, the greater is the absolute value of the difference.
3D Euler deconvolution: Theoretical basis for automatically selecting good solutions
Authors: Silva João B. C. , Barbosa Valéria C. F.
Published: November 2003

We derive the analytical estimators for the horizontal and vertical source positions in 3D Euler deconvolution as a function of the x‐, y‐, and z‐derivatives of the magnetic anomaly within a data window. From these expressions we show that, in the case of noise‐corrupted data, the x‐, y‐, and z‐coordinate estimates computed at the anomaly borders are biased toward the respective horizontal coordinate of the data window center regardless of the true or presumed structural indices and regardless of the magnetization inclination and declination. On the other hand, in the central part of the anomaly, the x‐ and y‐coordinate estimates are very close to the respective source horizontal coordinates regardless of the true or presumed structural indices and regardless of the magnetization inclination and declination. This contrasting behavior of the horizontal coordinate estimates may be used to automatically delineate the region associated with the best solutions. Applying the Euler deconvolution operator inside this region would decrease the dispersion of all position estimates, improving source location precision.