bluuebunny/crossref_metadata_2025 huggingface dataset:
Macrocyclic vs. dendrimeric effect. A DFT study
Authors: Soto‐Castro Delia , Guadarrama Patricia
Published: April 2004

Macrocycles up to 15 members with different heteroatoms (N, O, and S) and dendrimeric functionalized branches were assembled, resulting in unique “collective” supramolecular hosts with several active sites for transition metal ions complexation. The nature of the interactions between these kinds of systems and metal ions of the first transition series (Fe, Ni, Cu, Zn) was evaluated by calculations of the binding energies at the B3LYP/LACVP* level of theory, resulting in a preference of metal ions for macrocyclic cavity in terms of complexation; however, there is a favorable contribution in energy due to the cooperative effect of dendrimeric branches (DBs) in the inclusion process by means of long‐range interactions between metal ions and the heteroatoms present in DBs. According to calculated binding energies, even when the complexation in the middle of DBs appears as a less favored situation, still competes with the complexation occurred in several known macrocycles traditionally used in the formation of inclusion complexes. The capability of macrocycles as host entities is related to some criteria like: (1) the compatibility in orbital symmetry between host and guest molecules; (2) the cavity dimensions and the negative charge inside; and (3) the hardness–softness affinity between host and guest molecules. When DBs are included in host systems, their flexibility seems to be very important, in addition to localized negative charge, which permits the occurrence of long‐range interactions. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1215–1226, 2004
Hepatocyte‐specific gene expression from integrated lentiviral vectors
Authors: Nash Kathryn L. , Jamil Bushra , Maguire Alison J. , Alexander Graeme J. M. , Lever Andrew M. L.
Published: April 2004

Background

For many applications, efficient gene therapy will require long‐term, organ‐specific therapeutic gene expression. Lentiviral vectors based on HIV‐1 are promising gene delivery vehicles due to their ability to integrate transgenes into non‐dividing cells. Many experimental vectors express transgenes under the control of the cytomegalovirus (CMV) immediate‐early gene promoter. Although this promoter directs strong gene expression in vitro, it may be shut off rapidly in vivo. This study explores the potential of HIV‐1‐based vectors to transduce hepatocytes and compares gene expression from different promoters in integrated vectors.

Methods

HIV‐1‐based vector plasmids expressing the green fluorescent protein (GFP) under the control of the CMV promoter, the alpha‐1 antitrypsin gene promoter or promoters derived from the hepatitis B virus (HBV) genome were used to compare expression in transfected and transduced cell lines.

Results

Hepatocyte cell lines differed strikingly in their transfectability. Transduction with replication‐deficient HIV‐1‐based vector particles incorporating the different promoter elements was uniformly effective in hepatocyte and non‐hepatocyte lines. However, in hepatocytes, only the CMV, alpha‐1 antitrypsin and HBV core but not HBV surface promoters were able to produce GFP expression. Addition of the HBV enhancer 2 element improved the transducing ability of the HBV surface promoter and suppressed expression in non‐hepatocytes increasing specificity for hepatocytes.

Conclusions

Integrated lentiviral vectors can be used to direct transgene expression in liver cells both promiscuously and specifically. Promoters derived from the alpha‐1 antitrypsin gene or HBV are alternatives to the CMV promoter. Inclusion of the HBV enhancer 2 permits strong liver‐specific gene expression in vitro. Copyright © 2004 John Wiley & Sons, Ltd.
The influence of prior offender/victim relationship on offender stalking behavior
Authors: Groves Renee M. , Salfati C. Gabrielle , Elliot Deborah
Published: April 2004

The present study examined the influence of prior offender/victim relationship on offender stalking behavior. The actions that were present within the stalking offences were recorded using content analysis of victim and witness statements, and all other relevant material within the police files of 50 stalking cases. The sample was analyzed using a non‐metric multidimensional scaling procedure known as Smallest Space Analysis. The results suggested that when a prior sexual relationship existed between the offender and the victim the offender was more likely to engage in a majority of controlling style actions. However, an offender who did not have a prior sexual relationship with the victim was more likely to engage in a majority of infatuation style actions. Therefore, the study lends support to the influence of prior relationship on the actions that offenders engage in over the stalking period. Implications of the study and future research ideas are discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Molecular epidemiology of HIV in Ghana: Dominance of CRF02_AG
Authors: Fischetti Lucia , Opare‐Sem Ohene , Candotti Daniel , Sarkodie Francis , Lee Helen , Allain Jean Pierre
Published: April 2004

Recent studies showed the importance of CRF02_AG in West Africa, although the clinical relevance of these recombinant forms of HIV remains unknown. The present study aimed at determining the molecular diversity of HIV in Ghana and investigating the possible epidemiologic advantage of recombinant HIV‐1. Plasma samples collected in 1999–2002 from two populations of HIV infected individuals (144 asymptomatic candidate blood donors and 169 AIDS patients) were studied and 249 of them were molecularly characterised in gag, pol, and env regions. Five molecular groups were identified: strains clustering with CRF02_AG in all regions (147/249 or 59%), recombinant strains clustering with CRF02_AG in one or two regions (50/249 or 20%), other subtypes, pure or recombinant, but not involving CRF02_AG (37/249 or 15%), HIV‐2 (11/249 or 4.5%), and double infections (4/249 or 1.5%). There was no significant difference in the distribution of HIV‐1 recombinant strains according to clinical presentation. No evidence of a significant increase in CRF02_AG prevalence between 1999 and 2002 was found. Irrespective of clinical condition, CRF02_AG is the predominant molecular form of HIV‐1 in Kumasi, Ghana. J. Med. Virol. 73:158–166, 2004. © 2004 Wiley‐Liss, Inc.
Measurement of HIV RNA in patients infected by subtype C by assays optimized for subtype B results in an underestimation of the viral load
Authors: Gottesman Bat‐Sheva , Grosman Zehava , Lorber Margalit , Levi Itzchak , Shitrit Pnina , Mileguir Fernando , Gottesman Giora , Chowers Michal Y.
Published: April 2004

Quantitation assays of HIV‐1 RNA used currently were designed and optimized for subtype B viruses. However, infection with non‐B HIV viruses has become more common worldwide. Unfortunately, little information is available regarding the suitability of these assays for measurement of viral load in specific non‐B subtypes. The performance of two commercial HIV‐1 RNA quantitation assays was evaluated in 82 HIV subtype C‐infected patients and in 43 HIV‐1 subtype B‐infected patients. Blood samples were tested by the Amplicor HIV‐1 Monitor Assay, Version 1.5, and by the nucleic acid sequence‐based amplification HIV‐1 assay (NucliSens). The results were compared by using a paired, two‐tailed Student's t‐test; the difference between the assays was found to be significant only for subtype C. Discordant results (>0.5 log difference) between the two assays were detected in 39% of subtype C samples, compared to 23.2% of subtype B samples. In all cases in which a discordant result was detected, the lower results were obtained by the NucliSens assay. Discordant results between CD4 and viral load (CD4 < 200 cells/ml with a viral load <5,000 copies/ml) were observed in eight of the subtype C‐infected patients when a viral load was measured by NucliSens (9.7%), compared to three patients (3.6%) when measured by the Amplicor assay. In conclusion, in patients with HIV subtype C infection, measurement of HIV RNA by the NucliSens assay resulted in a significant underestimation of the viral load as compared to the Amplicor assay. As a consequence, such an underestimation may result in sub‐optimal care of patients infected with HIV subtype C. J. Med. Virol. 73:167–171, 2004. © 2004 Wiley‐Liss, Inc.
Transgenic tobacco cells producing the human monoclonal antibody to hepatitis B virus surface antigen
Authors: Yano Akira , Maeda Fumiko , Takekoshi Masataka
Published: April 2004

The recombinant human monoclonal antibody (MAb) against hepatitis B virus (HBV) surface antigen (HBsAg) was expressed in tobacco suspension cultures. The parental CL4MAb was produced by the Epstein–Barr virus (EBV) transformed human cell line TAPC301‐CL4. The CL4MAb cDNA was introduced into tobacco suspension cells by Agrobacterium mediated transformation. The monoclonal antibodies (MAbs), B294 and B303, which were derived from CL4 and subsequently produced in plant cells were selected for study. After purification on Protein A columns, B294 and B303 MAbs had anti‐HBs relative affinity constants similar to the parental CL4MAb. B303 MAb interacted with cell surface HBsAgs and showed complement‐dependent cytotoxicity in a manner that was similar to anti‐HBs human immunoglobulins (HBIg) that are used clinically. The results of this study point to the feasibility of producing MAbs to HBsAg in plants as an alternative to HBIg. J. Med. Virol. 73:208–215, 2004. © 2004 Wiley‐Liss, Inc.
Human astrovirus, norovirus (GI, GII), and sapovirus infections in Pakistani children with diarrhea
Authors: Phan Tung Gia , Okame Michio , Nguyen Tuan Anh , Maneekarn Niwat , Nishio Osamu , Okitsu Shoko , Ushijima Hiroshi
Published: April 2004

Fecal specimens from 517 infants and young children admitted to the Civil Karachi Hospital, Dow Medical College, Karachi city, Pakistan with acute gastroenteritis from 1990 to 1994 were collected and screened by RT‐PCR for human astrovirus (AstV), norovirus (NV), and sapovirus (SV). The specific epidemiological data for illness caused by these viruses in Pakistan are not available. AstV, NV, and SV were detected in 58, 51, and 17 of 517 fecal specimens, and this represented 11.2, 9.9, and 3.2%, respectively. An outbreak of gastroenteritis attributable to AstV serotype 1 was identified during September and October 1990. Moreover, one specimen with a triple mixed infection between AstV (serotypes 1 and 3) and NV GII was found. NV and SV were subjected to molecular analysis by sequencing. One of the sequenced specimens positive for SV turned out to be similar to a strain tentatively called a genogroup IV. The result underscores the importance of these viruses in association with acute gastroenteritis in Karachi city, Pakistan. J. Med. Virol. 73:256–261, 2004. © 2004 Wiley‐Liss, Inc.
Age related differences in humoral immune response to respiratory syncytial virus infection in adults
Authors: Walsh Edward E. , Falsey Ann R.
Published: April 2004

The humoral immune response to Respiratory Syncytial Virus (RSV) was investigated in old and young adults. RSV was identified by culture and/or reverse transcription polymerase chain reaction (RT‐PCR) in 52 elderly (mean age 74 years) and 15 young adults (mean age 33 years) with respiratory illness. Preinfection serum neutralizing and binding antibody levels were similar in the two age groups, although older persons had significantly greater serum neutralizing responses to group A RSV (log2 2.8 increase vs. 1.7, P = 0.001) and group B RSV (log2 2.8 vs. 1.3, P = 0.0008). Older persons also had significantly increased responses to the RSV F (log2 2.9 vs. 1.1, P < 0.0001), Ga (log2 2.1 vs. 1.3, P = 0.0007), and Gb proteins (log2 2.7 vs. 1.4, P = 0.0004). The exuberant antibody response seen in older adults may be a reflection of greater viral load and antigenic stimulation and/or a shift from Th1 to Th2 dominant immune response with aging. The relationship of immune response to disease pathogenesis in older persons deserves further study. J. Med. Virol. 73:295–299, 2004. © 2004 Wiley‐Liss, Inc.
Epidemiology of rotavirus diarrhoea in Iranian children
Authors: Khalili B. , Cuevas L.E. , Reisi N. , Dove W. , Cunliffe N.A. , Hart C.A.
Published: April 2004

Human rotavirus is the most important cause of severe diarrhoea in infants and young children worldwide. We describe the aetiology of viral diarrhoea and the characteristics of rotavirus infection in Shahrekord, Iran. Two hundred and fifty nine children <5 years old admitted to Hajar Hospital, 245 children with acute diarrhoea attending primary health centres in Shahrekord, and 114 children hospitalised for elective surgery were selected from October 2001 to August 2002. Stool samples were screened for enteric viruses using EM. Rotaviruses were characterised using ELISA, reverse transcription‐polymerase chain reaction (RT‐PCR), and electropherotyping. One hundred and eighty six viruses were identified, of which 146 (78%) were rotavirus. The second most frequent virus was coronavirus, followed by calicivirus. Rotaviruses exhibited a marked seasonal variation, being most frequently isolated from November to February (50% of rotavirus recovered) and affected mostly children <2 years old. The RT‐PCR successfully typed 139 of the 146 (95%) rotavirus G types and 124 (85%) P types. The most frequent P type was, P[8] in 108 (74%), P[4] in 16 (11%), and was P non‐typeable in 22 (15%). Among the G types, G1 was identified in 120 (82%), G2 in 19 (13%), and was G‐non‐typeable in 7 (5%). Our results are the first report of rotavirus genotypes affecting Iranian children. The most frequent G and P types (G1, G2, P[8], and P[4]) are similar to those reported from around the world and will be covered by existing rotavirus vaccines targeting G types G1–G4. J. Med. Virol. 73:309–312, 2004. © 2004 Wiley‐Liss, Inc.
Effects of neonatal capsaicin deafferentation on neuromuscular adjustments, performance, and afferent activities from adult tibialis anterior muscle during exercise
Authors: Dousset Erick , Marqueste Tanguy , Decherchi Patrick , Jammes Yves , Grelot Laurent
Published: April 2004

To investigate the role played by muscle afferents in the sensorimotor loops, we measured the effects of capsaicin injection in newborns on the mechano‐ and metabosensitive discharges and the running performance at adulthood. Female Sprague Dawley rats received a subcutaneous injection of either 50 mg/kg capsaicin or solvent (10% ethanol, 10% Tween 80 in 0.9% saline) during their second day of life. These two groups were compared with a control, untreated group. Four months later, treadmill running performance and muscle afferent (mechanosensitive and metabosensitive) activities from the tibialis anterior muscle were measured. The capsaicin‐treated group demonstrated a reduced maximal exercise capacity (time to exhaustion) and a reduced response of muscle metabosensitive fibers (group III and IV nerve endings) to the examined stimuli (arterial KCl and lactic acid injections, electrically induced fatigue) compared with the sham‐injected solvent and control groups. Group IV afferent responses were absent in the compound nerve action potentials evoked by peripheral nerve stimulation. The response to mechanosensitive fibers to tendon vibration was also affected in the capsaicin group compared with the control and sham‐injected groups, which presented a bimodal response corresponding to the activation of muscle spindles and Golgi tendon organs. Finally, measurements of the force developed by the tibialis anterior muscle from the beginning to the end of a 3‐min muscle stimulation revealed a more significant fall in the capsaicin group compared with the others. The present experiments reveal that the pharmacological alteration of muscular metabosensitive afferent resulted in drastic changes in the neuromuscular sensory encoding and in the central neural network that could accelerate failure of the task during fatigue. © 2004 Wiley‐Liss, Inc.
AMPA receptor subunit expression in chick vestibular nucleus neurons
Authors: Popratiloff Anastas , Wang Ya‐Xian , Narvid Jared , Petralia Ronald S. , Giaume Christian , Peusner Kenna D.
Published: April 2004

The principal cells of the chick tangential nucleus are vestibular nucleus neurons whose responses on vestibular nerve stimulation are abolished by glutamate receptor antagonists. Using confocal microscopy, we quantified immunolabeling for AMPA receptor subunits GluR1, GluR2, GluR2/3, and GluR4 in principal cells that were identified by the neuronal marker, microtubule‐associated protein 2 (MAP2). This work was focused primarily on 9 days after hatching (H9) when the principal cells have acquired some important mature electrophysiologic properties. At H9, the principal cell bodies stained strongly with GluR2/3 and GluR4, whereas GluR1 and GluR2 produced weak signals. Moreover, GluR2/3 and GluR4 receptor subunit clusters in principal cell bodies and dendrites were localized at sites contacted by biocytin‐labeled vestibular nerve terminals and synaptotagmin‐labeled terminals. Developmental expression of AMPA receptor immunolabeling was studied in the principal cell bodies at embryonic day 16 (E16) and hatching (H1). At E16, labeling for GluR4 was already strong, and continued to increase at H1 and H9. In contrast, GluR2/3 labeling was weak at E16, but increased significantly at H1, and more so by H9. GluR1 and GluR2 were present at low levels at E16 and H1. From E16 to H9, overall AMPA receptor subunit expression increased steadily, with H9 showing the strongest labeling. Ultrastructural observations at E16 and H3 confirmed the presence of immunogold labeling for AMPA receptor subunits at the vestibular nerve and non‐vestibular nerve synapses on the principal cell bodies. In summary, these results indicate that GluR3 and GluR4 are the major AMPA receptor subunits involved in excitatory synaptic transmission in principal cells during the perinatal period. © 2004 Wiley‐Liss, Inc.
Triblock Copolymers Based on 1,3‐Trimethylene Carbonate and Lactide as Biodegradable Thermoplastic Elastomers
Authors: Zhang Zheng , Grijpma Dirk W. , Feijen Jan
Published: April 2004

Summary: Biodegradable triblock copolymers based on 1,3‐trimethylene carbonate (TMC) and different lactides (i.e. D,L‐lactide(DLLA), L‐lactide (LLA), D‐lactide (DLA)) designated as poly(DLLA‐TMC‐DLLA), poly(LLA‐TMC‐LLA) and poly(DLA‐TMC‐DLA) were prepared and their mechanical and thermal properties were compared with those of high molecular weight poly(TMC) and poly(TMC‐co‐DLLA) statistical copolymers. Triblock copolymers containing crystallizable LLA or DLA segments perform as thermoplastic elastomers (TPEs) when the poly(lactide) blocks are long enough to crystallize. In blends of poly(LLA‐TMC‐LLA) and poly(DLA‐TMC‐DLA) triblock copolymers, stereo‐complex formation between the enantiomeric poly(lactide) segments occurs as demonstrated by differential scanning calorimetry and light microscopy. These blends have good tensile properties and excellent resistance to creep under static and dynamic loading conditions.

Permanent deformation (after 2 h recovery) of compression‐molded poly(TMC) and solvent‐cast poly(LLA‐TMC‐LLA) and poly(ST‐TMC‐ST) films.

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Permanent deformation (after 2 h recovery) of compression‐molded poly(TMC) and solvent‐cast poly(LLA‐TMC‐LLA) and poly(ST‐TMC‐ST) films.
Spinodal Decomposition in Binary Blend of Poly(methyl methacrylate)/Poly(α‐methyl styrene‐co‐acrylonitrile): Analysis of Early and Late Stage Demixing
Authors: Madbouly Samy A. , Ougizawa Toshiaki
Published: April 2004

Summary: The phase separation kinetics of a poly(methyl methacrylate), PMMA, and poly(α‐methylstyrene‐co‐acrylonitrile), PαMSAN, blend exhibiting a LCST‐type phase diagram have been investigated as functions of temperature and demixing time for the near critical composition (PαMSAN/PMMA = 25:75) using a time‐resolved light scattering technique. We found that the scattering data in the early stage spinodal decomposition (SD) can be well described by the linearized Cahn–Hilliard theory. Spinodal temperature Ts ∼ 171 °C was determined from Dapp versus T and q versus T based on the analysis of Cahn theory in the early stage SD, where Dapp is the apparent diffusion coefficient and qm is the scattering vector at the maximum scattering intensity. The value of Ts obtained from the analysis of light scattering data was in good agreement with the phase diagram obtained visually at the equilibrium condition. The LCST‐type phase diagram of this blend was also calculated using the Flory–Huggen theory. The estimated interaction parameter used for the calculation of the phase diagram was found to be composition and temperature dependent. The coarsening behavior of the blend at the late stage SD was also studied by analyzing the magnitudes of qm and Im at various demixing times and temperatures based on the nonlinear statistical theories. Both of qm and Im obtained at different times and temperatures can be superposed and reduced to the respective master curves by horizontal shifting when they are plotted against log (t/aT) at a given reference temperature, where aT is the temperature‐dependent shift factor. The shape of the phase separation domain structures as a function of time during the SD was also considered. The scaling structure function F(x,t;T) = qm(t;T)3I(q,t;T) versus q/qm was found to be time independent and falls onto a universal curve in the late stage SD as a result of the dynamical self‐similarity accompanying with the phase separation process.

Optical microscopy pictures for the structure development of spinodal decomposition for PαMSAN/PMMA = 25:75 blend at 180 °C for different demixing times.

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Optical microscopy pictures for the structure development of spinodal decomposition for PαMSAN/PMMA = 25:75 blend at 180 °C for different demixing times.
Customer‐oriented selling: Exploring the roles of emotional intelligence and organizational commitment
Authors: Rozell Elizabeth J. , Pettijohn Charles E. , Parker R. Stephen
Published: April 2004

Professional salespeople are often placed in situations where role conflict and ambiguity are prevalent. They are generally expected to sell a firm's products and services to generate immediate profits, while simultaneously building customer satisfaction and promoting lifetime customers and the long‐term economic viability of the firm. The concept of customer‐oriented selling illustrates the conflict, as salespeople are required to forgo immediate benefits in lieu of long‐term rewards. The purpose of this study was to determine the relationships existing between customer‐oriented selling, emotional intelligence, and organizational commitment. The results indicate that a salesperson's customer orientation level is significantly related to emotional intelligence. Implications of the findings indicate that managers should consider using emotional intelligence as a selection and human‐resource development tool, as improvements in emotional intelligence are correlated with greater levels of customer orientation. © 2004 Wiley Periodicals, Inc.
Action control, proxy control, and consumers' evaluations of the service exchange
Authors: Namasivayam Karthik
Published: April 2004

This article adopts a consumer's point of view, and extends current literature that models the relationships between consumers' control perceptions, service providers' fair behaviors, and consumers' satisfaction with the exchange. Perceived control is disassembled into action and proxy control and their differential actions in the service exchange discussed. This article models, for the first time, the joint effects of perceived control and service provider behaviors on consumer satisfaction by explicitly connecting service‐provider fair behaviors to consumers' perceptions of control. The results from two repeated‐measures experiments provide support for the hypotheses. Specifically, a multivariate analysis of the data demonstrated main effects for the experimental manipulations on perceived control, perceived fairness, satisfaction, and behavioral intentions. An interaction effect between perceived control and perceived fairness was also evident in one experiment. Future research and managerial implications are discussed. © 2004 Wiley Periodicals, Inc.
Natural history and syndromic associations of orthostatic tremor: A review of 41 patients
Authors: Gerschlager Willibald , Münchau Alexander , Katzenschlager Regina , Brown Peter , Rothwell John C. , Quinn Niall , Lees Andrew J. , Bhatia Kailash P.
Published: April 2004

Orthostatic tremor (OT) is a rare condition characterized by unsteadiness when standing still that is relieved when sitting or walking and is thought to arise from a central generator in the cerebellum or brainstem. OT is considered to be a distinct, discrete condition, and little is known about its demographic characteristics, natural history, associated features, and treatment response. We have reviewed these aspects in 41 OT patients fulfilling current diagnostic criteria, seen at our institution between 1986 and 2001. We classified 31 (75%) as having idiopathic “primary OT” either with (n = 24) or without an associated postural arm tremor. We found that 10 of 41 (25%) cases had additional neurological features, and we defined this group as having “OT plus” syndrome. Of these 10, 6 had parkinsonism; 4 of these had typical Parkinson's disease (PD), 1 had vascular and 1 had drug‐induced parkinsonism. Among the remaining 4 patients, 2 had restless legs syndrome (RLS), 1 had tardive dyskinesia, and 1 orofacial dyskinesias of uncertain etiology. One patient with PD and the patient with vascular parkinsonism also had RLS. Age at onset was significantly earlier in the “primary OT” (mean ± SD, 50.4 ± 15.1) than in the “OT plus” (61.8 ± 6.4; z = 2.7; P = .006) group. In 7 of the 10 “OT plus” patients, OT leg symptoms preceded the onset of additional neurological features. OT appeared to be underdiagnosed, and on average, it took 5.7 years from the initial complaints until a diagnosis was made. In general, treatment response to a variety of drugs such as clonazepam, primidone, and levodopa was poor. In most cases, OT symptoms remain relatively unchanged over the years, but in 6 of 41 cases (15%), the condition gradually worsened over the years, and in some of these cases, symptoms spread proximally to involve the trunk and arms. OT may not be a discrete disorder as commonly believed and associated features like parkinsonism present in nearly 25% of cases. Dopaminergic dysfunction may have a role in the pathophysiology of this disorder. © 2004 Movement Disorder Society
Weak solutions for time‐dependent boundary integral equations associated with the bending of elastic plates under combined boundary data
Authors: Chudinovich Igor , Constanda Christian , Gómez Eduardo Aguilera
Published: April 2004

The existence, uniqueness, stability, and integral representation of distributional solutions are investigated for the equations of motion of a thin elastic plate with a combination of displacement and moment‐stress components prescribed on the boundary. Copyright © 2004 John Wiley & Sons, Ltd.
Global controllability between steady supercritical flows in channel networks
Authors: Gugat Martin , Leugering Günter , Schmidt E. J. P. Georg
Published: April 2004

We consider a tree‐like network of open channels with outflow at the root. Controls are exerted at the boundary nodes of the network except for the root. In each channel, the flow is modelled by the de St. Venant equations. The node conditions require the conservation of mass and the conservation of energy. We show that the states of the system can be controlled within the entire network in finite time from a stationary supercritical initial state to a given supercritical terminal state with the same orientation. During this transition, the states stay in the class of C1‐functions, so no shocks occur. Copyright 2004 John Wiley & Sons, Ltd.
Asymptotic behaviour of the energy for electromagnetic systems with memory
Authors: Muñoz Rivera Jaime E. , Grazia Naso Maria , Vuk Elena
Published: April 2004

Some linear evolution problems arising in the theory of hereditary electromagnetism are considered here. Making use of suitable Liapunov functionals, existence of solutions as well as asymptotic behaviour, are determined for rigid conductors with electric memory. In particular, we show the polynomially decay of the solutions, when the memory kernel decays exponentially or polynomially. Copyright © 2004 John Wiley & Sons, Ltd.
Adaptive stabilization of the sine‐Gordon equation by boundary control
Authors: Kobayashi Toshihiro
Published: April 2004

This paper is concerned with adaptive global stabilization of the sine‐Gordon equation without damping by boundary control. An adaptive stabilizer is constructed by the concept of high‐gain output feedback. The closed‐loop system is shown to be locally well‐posed by the Banach fixed point theorem and then to be globally well‐posed by the Lyapunov method. Moreover, using a multiplier method global exponential stabilization of the system is proved. Copyright © 2004 John Wiley & Sons, Ltd.
Differential isolation of a gyroelectric InSb disc
Authors: Ng Zee M. , Davis Lionel E. , Sloan Robin
Published: April 2004

A 15‐GHz InSb circulator supported with microstrip‐slotline transitions is reported for the first time. The device showed a differential isolation of 15 dB over a fractional bandwidth of 6.7% at a temperature of 77°K with bias flux density of 0.78 Tesla. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 433–434, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20161
Polarization‐dependent electromagnetic band gap (PDEBG) structures: Designs and applications
Authors: Yang Fan , Rahmat‐Samii Yahya
Published: April 2004

EBG structures exhibit an in‐phase reflection coefficient, which makes them desirable for low‐profile antenna designs. However, a conventional EBG structure has an identical reflection phase for a normally incident plane wave in spite of its polarization state. This paper presents novel polarization‐dependent EBG (PDEBG) structures whose reflection phases are different, depending upon the polarization state of the incident plane wave. This polarization‐dependent reflection‐phase feature is realized by changing the unit geometries, for example, by using a rectangular patch to replace the square patch, by cutting slots into the patch, or by offsetting the vias. By properly tailoring the phase difference between different polarizations, a useful EBG reflector is introduced, which can control the polarization state of the reflected wave. One attractive application of this reflector is that the reflected wave of a circularly polarized incident plane wave can maintain its polarization sense. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 439–444, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20164
Evaluation of time‐domain OCDMA performances using a Gaussian model for an optical amplified channel
Authors: Lourdiane Mounia , Gallion Philippe B. , Vallet Robert A.
Published: April 2004

The performances of time‐domain optical code‐division multiple access (OCDMA), using a Gaussian model for an optical amplified channel, are evaluated. Interest in spectral spreading to take advantage of low‐cost optical filtering conditions is pointed out and the simultaneous effects of multiaccess interference (MAI) and optical noise on optical detection are demonstrated. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 463–465, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20172
Simulation and measurements of current‐injected gain control in semiconductor optical amplifiers
Authors: Gallep Cristiano M. , Bordonalli Aldário C. , Conforti Evandro
Published: April 2004

A semiconductor optical amplifier simulator (SOASim), used to analyze in‐line optical amplifiers, current‐injected space switches, and electro‐optical regenerators, is presented. The effects of amplitude‐modulated injected current in the techniques of feed‐forward gain control (FFGC) and pre‐impulse‐step injected current (PISIC) are included. Experimental results are in good agreement with simulations. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 477–481, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20177
Nonuniform layer model of an image‐guide millimeter‐wave phase shifter
Authors: Fickenscher T. , Schwolen A.
Published: April 2004

Optically controllable millimeter‐wave phase shifters in image‐guide technology with rectangular dielectric strips made of semiconductor material are investigated with special regard to the inherent diffusion‐controlled nonuniform plasma‐density distribution due to bandgap‐radiation excitation. This analysis is based on the effective dielectric constant (EDC) method. Numerical examples are presented and discussed, taking single‐moded Si and GaAs image guides at W‐band frequencies into consideration. Furthermore, low‐loss silicon‐on‐quartz sandwich structures are proposed and analysed for use in image‐guide phase shifters. It is clearly observed that phase shifters designed for low loss and high phase shift will require a sandwich structure with a thin plasma layer. The results obtained for the image‐guide phase shifter are compared to those for the dielectric‐waveguide phase shifter. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 486–490, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20180
A wavelet‐based radial‐basis function neural network approach to the inverse scattering of conducting cylinders
Authors: Aşık Ulaş , Günel Tayfun , Erer Işın
Published: April 2004

A new approach, based on the radial‐bias function neural network (RBF‐NN) combined with wavelet transform, is presented for the estimation of the locations and radii of conducting cylindrical scatterers. The discrete wavelet transform coefficients of the electric‐field values scattered by the cylinder are fed into the RBF‐NN, whose outputs are the location and the radius of the cylinder. The efficiency of the proposed approach is compared with the approach where the field values are directly used. The performance of the wavelet‐based approach for noisy field measurements is also investigated. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 506–511, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20186
Experimental investigation of a tri‐band frequency‐selective surface
Authors: Sarkar D. , Sarkar P. P. , Chowdhury S. K.
Published: April 2004

The frequency‐selective property of an array of rectangular dipole microstrip patches, resonant at two frequencies in the J band and two other frequencies in the Ku band, has been investigated experimentally. Measured data indicate that the electromagnetic wave transmits well through the frequency‐selective surface (FSS) in the frequency range of 8.2 to 11.4 GHz and scatters well (around 20 dB) from the FSS in the frequency ranges of 6.3 to 7.7 GHz and 12.4 to 13.9 GHz. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 511–512, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20187
A dual‐frequency dual‐polarized microstrip antenna fed by an inclined slot
Authors: Row Jeen‐Sheen
Published: April 2004

This paper presents the design of a single‐feed microstrip antenna with dual‐frequency and dual‐polarization operations. Two fundamental modes, TM01 and TM10, are excited in a single long rectangular patch through an inclined slot to achieve the two operating frequency bands centered at 2.43 and 5.2 GHz, respectively. To increase the bandwidths of the two operating frequency bands, the resonant slot and additional parasitic patches are used to couple with the TM01 and TM10 modes, respectively. The experimental results show that 10‐dB impedance bandwidths of 5% and 23% are obtained for the two operating frequency bands. Good agreement is also observed between the measured and simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 512–514, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20188
Perfusion MRI of U87 brain tumors in a mouse model
Authors: Sun Yanping , Schmidt Nils O. , Schmidt Karl , Doshi Sameer , Rubin Joshua B. , Mulkern Robert V. , Carroll Rona , Ziu Mateo , Erkmen Kadir , Poussaint Tina Y. , Black Peter , Albert Mitchell , Burstein Deborah , Kieran Mark W.
Published: April 2004

Continuous arterial spin labeling (CASL) was used to obtain an index of cerebral blood flow (ICBF) in the normal mouse brain and in an orthotopic mouse model of human U87 high‐grade glioma at 8.5 T. Under the assumption of a constant tissue:blood partition coefficient for water in different tissues, the mean ICBF (n = 14) was found to be 50 ± 9 mL/100g/min for tumor core and 209 ± 11 mL/100g/min for normal tissue. The apparentT1(T1app) was 2.01 ± 0.06 sec for tumor core and 1.66 ± 0.03 sec for normal tissue. The ICBF and theT1appvalues were significantly different (P< 0.001) between these two regions. The detailed changes of ICBF andT1appin the transition from the tumor core through the tumor periphery to surrounding tissue were studied. Immunohistochemistry indicated that tumor vascularity was not uniform, with microvessel density highest in normal brain and the tissue surrounding the tumor and lowest in the tumor core. The large difference in ICBF between the tumor core and normal tissue suggests that this index might be useful for the assessment of the efficacy of antiangiogenic therapy. Magn Reson Med 51:893–899, 2004. © 2004 Wiley‐Liss, Inc.
Determination of intracellular pH and compartmentation using diffusion‐weighted NMR spectroscopy with pH‐sensitive indicators
Authors: Cohen Jack S. , Motiei Menachem , Carmi Shani , Shiperto Dana , Yefet Odeya , Ringel Israel
Published: April 2004

The intracellular pH (pHi) of a series of cancer cell lines was determined using the pH‐sensitive indicators imidazole (Im) or histidine (His) and diffusion‐weighted (DW) proton NMR spectroscopy. The DW method allows the observation at high magnetic field gradient values of only the slow‐moving (intracellular) components, thus ensuring complete separation between intra‐ and extracellular components. Using the chemical shift difference (Δδ) between the imidazole ring C2‐H and C4(5)‐H peaks, we were able to measure the pHi independently of chemical shift standardization. With His, the cell lines gave pHi values of ∼6.5–7.0, whereas with Im, a second, more acidic compartment (pHi = 5.5–5.8) was also observed. An inverse correlation was also found between pHi and the intracellular lactate concentration. This method may be applicable to in vivo pH determinations. Magn Reson Med 51:900–903, 2004. © 2004 Wiley‐Liss, Inc.
Artifact reduction in undersampled projection reconstruction MRI of the peripheral vessels using selective excitation
Authors: Du J. , Thornton F.J. , Fain S.B. , Korosec F.R. , Browning F. , Grist T.M. , Mistretta C.A.
Published: April 2004

The projection reconstruction (PR)‐HyperTRICKS (time resolved imaging of contrast kinetics) acquisition integrates the benefits of through‐plane Cartesian slice encoding and in‐plane undersampled PR. It provides high spatial resolution both in‐plane (about 1 mm2) and through‐plane (1–2 mm), as well as relatively high temporal resolution (about 0.25 frames per second). However, undersampling artifacts that originate from anatomy superior or inferior to a coronal imaging FOV may severely degrade the image quality. In coronal MRA acquisitions, the slice coverage is limited in order to achieve high temporal resolution. In this report we describe an artifact reduction method that uses selective excitation in PR‐HyperTRICKS. This technique significantly reduces undersampling streak artifacts while it increases the slice coverage. Magn Reson Med 51:1071–1076, 2004. © 2004 Wiley‐Liss, Inc.
MRI monitoring of heating produced by ultrasound absorption in the skull: In vivo study in pigs
Authors: McDannold Nathan , King Randy L. , Hynynen Kullervo
Published: April 2004

The purpose of this study was to test the utility of MR thermometry for monitoring the temperature rise on the brain surface and in the scalp induced by skull heating during ultrasound exposures. Eleven locations in three pigs were targeted with unfocused ultrasound exposures (frequency = 690 kHz; acoustic power = 8.2–16.5 W; duration = 20 s). MR thermometry (a chemical shift technique) showed an average temperature rise in vivo of 2.8°C ± 0.6°C and 4.4°C ± 1.4°C on the brain surface and scalp, respectively, at an acoustic power level of 10 W. The temperature rise on the scalp agreed with that measured with a thermocouple probe inserted adjacent to the skull (average temperature rise = 4.6°C ± 1.0°C). Characterization of the transducer showed that the average acoustic intensity was 1.3 W/cm2 at an acoustic power of 10 W. The ability to monitor the temperature rise next to the skull with MRI‐based thermometry, as shown here, will allow for safety monitoring during clinical trials of transcranial focused ultrasound. Magn Reson Med 51:1061–1065, 2004. © 2004 Wiley‐Liss, Inc.
Measuring blood volume and vascular transfer constant from dynamic, T‐weighted contrast‐enhanced MRI
Authors: Johnson Glyn , Wetzel Stephan G. , Cha Soonmee , Babb James , Tofts Paul S.
Published: April 2004

Dynamic, contrast‐enhanced MRI (deMRI) is increasingly being used to evaluate cerebral microcirculation. There are two different approaches for analyzing deMRI data. Intravascular indicator dilution theory has been used to estimate blood volume (and perfusion), usually from T2‐ or T‐weighted images of the first pass of the bolus. However, the theory assumes that the tracer (i.e., contrast agent) remains intravascular, which is often not the case when the blood–brain barrier (BBB) is damaged. Furthermore, the method provides no information on the vascular transfer constant. Pharmacokinetic modeling analyses of T1‐weighted images after first pass do give values of the vascular transfer constant and the volume of the extravascular, extracellular space (EES), but they generally are unable to give estimates of blood volume. In this study we apply pharmacokinetic modeling to dynamic T‐weighted imaging of the first pass of a tracer bolus. This method, which we call first‐pass pharmacokinetic modeling (FPPM), gives an estimate of the blood volume, vascular transfer constant, and EES volume. The method was applied to a group of 26 patients with surgically proven tumors (10 glioblastomas multiforme (GBMs), six lymphomas, and 10 meningiomas). The measurements of the blood volume and transfer constant were consistent with the known physiology of these tumors. Magn Reson Med 51:961–968, 2004. © 2004 Wiley‐Liss, Inc.
Method for rapid MRI needle tracking
Authors: Kochavi Eyal , Goldsher Dorith , Azhari Haim
Published: April 2004

A new method for MRI needle tracking within a given two‐dimensional (2D) image slice is presented. The method is based on k‐space investigation of the difference image between the current dynamic frame and a reference frame. Using only a few central k‐lines of the difference image and a nonlinear optimization procedure, one can resolve the parameters that define the 2D sinc function that best characterizes the needle in k‐space. The spatial location and orientation of the needle are determined from these parameters. Rapid needle tracking is obtained by repeated acquisitions of the same set of several central k‐lines (as in a “keyhole” protocol) and repeated computation of these parameters. The calculated needle tip is depicted on the reference image by means of a graphic overlay. The procedure was tested in computer simulations and in actual MRI scans (the computations were done offline). It was demonstrated that six k‐lines out of 128 usually suffice to locate the needle. The refresh rate of the needle location depends on the time required to sample the subset of k‐lines, calculate the current needle location, and refresh the reference image. Magn Reson Med 51:1083–1087, 2004. © 2004 Wiley‐Liss, Inc.
Comparison of BOLD contrast and Gd‐DTPA dynamic contrast‐enhanced imaging in rat prostate tumor
Authors: Jiang Lan , Zhao Dawen , Constantinescu Anca , Mason Ralph P.
Published: April 2004

The microcirculation and oxygenation of a tumor play important roles in its responsiveness to cytotoxic treatment, and noninvasive assessments of its vascular properties may have prognostic value. Dynamic contrast‐enhanced (DCE) 1H MRI based on infusion of Gd‐DTPA, and blood oxygen level‐dependent (BOLD) contrast based on altering inhaled gas are both sensitive to vascular characteristics. This study compares the effects observed in eight Dunning prostate R3327‐AT1 rat tumors imaged sequentially at 4.7 Tesla by echo‐planar imaging (EPI). Both interventions generated a significant response, and each revealed significant differences between the center and periphery of the tumors. On a voxel‐by‐voxel basis across the whole tumor population, there was a close correlation between the maximum rate of signal response and the magnitude of response to each intervention (R2 ≥ 0.6, P < 0.0001). However, when the data were analyzed separately for each individual tumor, some showed a weak correlation (R2 < 0.4), particularly for DCE, and the nature (slope) varied between separate tumors. Generally, there was a weak correlation (N = 7, R2 < 0.5) between responses to the two interventions on a tumor‐by‐tumor basis, which emphasizes that the techniques are not equivalent. Both techniques revealed intra‐ and intertumor heterogeneity, but the BOLD response was more rapidly reversible than the DCE response. This suggests that the BOLD technique may be a useful tool for investigating interventions (such as drugs) that cause vascular disruption. Magn Reson Med 51:953–960, 2004. © 2004 Wiley‐Liss, Inc.
Characterizing non‐gaussian diffusion by using generalized diffusion tensors
Authors: Liu Chunlei , Bammer Roland , Acar Burak , Moseley Michael E.
Published: April 2004

Diffusion tensor imaging (DTI) is known to have a limited capability of resolving multiple fiber orientations within one voxel. This is mainly because the probability density function (PDF) for random spin displacement is non‐Gaussian in the confining environment of biological tissues and, thus, the modeling of self‐diffusion by a second‐order tensor breaks down. The statistical property of a non‐Gaussian diffusion process is characterized via the higher‐order tensor (HOT) coefficients by reconstructing the PDF of the random spin displacement. Those HOT coefficients can be determined by combining a series of complex diffusion‐weighted measurements. The signal equation for an MR diffusion experiment was investigated theoretically by generalizing Fick's law to a higher‐order partial differential equation (PDE) obtained via Kramers‐Moyal expansion. A relationship has been derived between the HOT coefficients of the PDE and the higher‐order cumulants of the random spin displacement. Monte‐Carlo simulations of diffusion in a restricted environment with different geometrical shapes were performed, and the strengths and weaknesses of both HOT and established diffusion analysis techniques were investigated. The generalized diffusion tensor formalism is capable of accurately resolving the underlying spin displacement for complex geometrical structures, of which neither conventional DTI nor diffusion‐weighted imaging at high angular resolution (HARD) is capable. The HOT method helps illuminate some of the restrictions that are characteristic of these other methods. Furthermore, a direct relationship between HOT and q‐space is also established. Magn Reson Med 51:924–937, 2004. © 2004 Wiley‐Liss, Inc.