bluuebunny/crossref_metadata_2025 huggingface dataset:
A new method to locate saddle points for reactions in solution by using the free‐energy gradient method and the mean field approximation
Authors: Galván I. Fdez. , Martín M. E. , Aguilar M. A.
Published: April 2004

A new method for calculating saddle points of reactions in solution is presented. The main characteristics of the method are: (1) the solute–solvent system is described by the averaged solvent electrostatic potential/molecular dynamics method (ASEP/MD). This is a quantum mechanics/molecular mechanics method (QM/MM) that makes use of the mean field approximation (MFA) and that permits one to simultaneously optimize the electronic structure and geometry of the solute molecule and the solvent structure around it. (2) The transition state is located by the joint use of the free‐energy gradient method and the mean field approximation. An application to the study of the Menshutkin reaction between NH3 and CH3Cl in aqueous solution is discussed. The accuracy and usefulness of the proposed method is checked through comparison with other methods. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1227–1233, 2004
Reaction pathways and projection operators: Application to string methods
Authors: Quapp Wolfgang
Published: April 2004

The reaction path is an important concept of theoretical chemistry. We discuss the definition with the help of diverse projection operators for the intrinsic reaction coordinate (IRC), for the following of the reduced gradient (RGF) or Newton trajectory (NT), and for the Gradient Extremal (GE). We describe different numerical schemes for the definitions in the context of string methods. It comes out that Newton trajectories are the best ansatz for a string method. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1277–1285, 2004
Mechanism for ribonucleotide reductase inactivation by the anticancer drug gemcitabine
Authors: Pereira Susana , Fernandes Pedro Alexandrino , Ramos Maria João
Published: April 2004

Gemcitabine (2′,2′‐difluoro‐2′‐deoxycytidine, dFdC) is a very promising anticancer drug, already approved for clinical use in three therapeutic indications. It is metabolized intracellularly to 5′‐diphosphate (dFdCDP), which is known to be a potent inhibitor of ribonucleotide reductase (RNR). Although several nucleotide analogs show in vitro capacity of RNR inactivation, none has shown the in vivo efficacy of dFdCDP. Accordingly, the experimental data suggests that its mechanism of inhibition is different from the other known RNR suicide inhibitors. Enzyme inhibition in the absence of reductive species leads to complete loss of the essential radical in subunit R2, and formation of a new nucleotide‐based radical. Interestingly, however, the presence of the reductants does not prevent inhibition—the radical is not lost but the targeted subunit of RNR becomes R1, which is inactivated possibly by alkylation. We have conducted a theoretical study, which led us to the first proposal of a possible mechanism for RNR inhibition by dFdCDP in the absence of reductants. This mechanism turned out to be very similar to the natural substrate reduction pathway and only deviates from the natural course after the formation of the well‐known disulphide bridge. This deviation is caused precisely by the F atom in the β‐face, only present in this inhibitor. The essential radical in R2 is lost, and so is the enzyme catalytic activity. The nucleotide‐based radical that constitutes the end product of our mechanism has been suggested in the literature as a possible candidate for the one detected experimentally. In fact, all experimental data available has been reproduced by the theoretical calculations performed here. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1286–1294, 2004
Prevalence of hepatitis A antibodies in schoolchildren in Catalonia (Spain) after the introduction of universal hepatitis A immunization
Authors: Domínguez Àngela , Bruguera Miquel , Plans Pere , Costa Josep , Salleras Lluís
Published: April 2004

The objective of this study was to investigate the prevalence of hepatitis A antibodies (anti‐HAV) in schoolchildren in Catalonia and to compare it with the rates found in previous studies. Sera from a representative sample of 1,342 children aged between 6 and 15 years, recruited in 2001, were tested for anti‐HAV. The results were related to sociodemographic variables and vaccination history. The overall prevalence of anti‐HAV was 51.4%. The prevalence was 5.5% in non‐vaccinated children, similar to that found in a 1996 study, and 96.6% in vaccinated children. The prevalence of anti‐HAV in non‐vaccinated children increased significantly with age, reaching 11.6% in the 13–15 years age group. The prevalence of anti‐HAV was higher in children born outside Catalonia than in those born in Catalonia (16.1% vs. 5.0%, P = 0.02). The expected continuation in the decline in the prevalence of anti‐HAV in non‐vaccinated schoolchildren, observed in Catalonia since 1986, was not found in 2001. The rate of anti‐HAV in 2001 was slightly higher than in 1996, although the difference was not statistically significant (5.5 and 3.5%, respectively). This could be explained by the increased number of recent immigrant children born outside Catalonia, mainly in countries where hepatitis A is highly endemic. J. Med. Virol. 73:172–176, 2004. © 2004 Wiley‐Liss, Inc.
Reduction of double‐stranded RNA‐activated protein kinase in hepatocellular carcinoma associated with hepatitis B virus
Authors: Chen George G. , Lai Paul B.S. , Ho Rocky L.K. , Chan Paul K.S. , Xu H. , Wong John , Lau Wan Y.
Published: April 2004

Chronic hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) in Asia. Double‐stranded RNA (dsRNA)‐activated protein kinase (PKR) is an interferon‐induced, serine/threonine protein kinase. Recent studies have suggested that PKR is involved in the pathogenesis of HCC with hepatitis virus C infection by inhibiting viral and cellular proteins related to cell growth and proliferation. In the present study, PKR was examined in both tumor and non‐tumor tissues from HCC livers infected with HBV. The expression of PKR was determined by TaqMan real‐time PCR and immunohistochemical methods. The level of PKR was also analyzed in relation to pathological changes observed in HCC. The result showed that PKR was reduced in tumor tissues of HCC from HBV carriers with low serum viral load (<0.7 × 106 copies/ml) compared to those with higher serum viral load. However, the overall PKR level was much lower in tumor tissues than that in non‐tumor tissues, irrespective of HBV carrier status or serum viral load. PKR level tended to be lower in HCC samples with alpha‐fetoprotein (AFP) more than 500 ng/ml (mean: 4024.2 ng/ml) than those with AFP less than 500 ng/ml (mean: 50.6 ng/ml). There was no significant difference in the expression of PKR between tumor tissues with well differentiation and those with poor or moderate differentiation. In conclusion, the level of PKR was reduced in HCC tumor tissues, suggesting a possible role of PKR in promoting the growth of tumor. HBV may participate in altering the level of PKR, but factors other than HBV should play a more determining role in the regulation of PKR in HCC. The association between PKR and AFP levels may offer an alternative tumor marker for HCC. J. Med. Virol. 73:187–194, 2004. © 2004 Wiley‐Liss, Inc.
Quantitation of cytomegalovirus DNA by the polymerase chain reaction as a predictor of disease in solid organ transplantation
Authors: Ghisetti Valeria , Barbui Anna , Franchello Alessandro , Varetto Silvia , Pittaluga Fabrizia , Bobbio Marco , Salizzoni Mauro , Marchiaro Giovanna
Published: April 2004

Cytomegalovirus (CMV) infection is an important cause of morbidity in solid organ recipients. Early markers to identify the progress of the infection and patients at high risk are required in order to apply a strategy of pre‐emptive therapy. The efficacy of pre‐emptive therapy relies on accurate laboratory tests to monitor CMV infection. The evaluation of CMV DNA kinetics by the polymerase chain reaction (PCR) is widely used for the management of CMV infection but markers predicting the progression of the infection and standardization of the technique are essential for the clinical interpretation of PCR results. A commercially available PCR system, the COBAS AMPLICOR Monitor (Roche Diagnostics, Brachburg, NJ), was used for the quantitation of CMV DNA in weekly blood samples (n = 504) from 47 solid organ recipients in the first 6 months after transplantation. PCR results were evaluated according to the development of clinical disease in order to find a DNA threshold and time points predicting the progression of CMV infection. Week 4 from transplantation was the earliest time point to note a significant difference between those patients who eventually developed CMV disease (n = 30) and those who remained asymptomatically infected (n = 17). At week 4, viral loads were significantly higher in patients who developed CMV disease than in asymptomatic infections (median value: 4 log10/106 leukocytes vs. 2.8, P < 0.0001). At week 4, a DNA level ≥4 log10/106 leukocytes was associated with a 45.37 odds ratio for CMV disease. Any increase ≥1 log from the first DNA detection to week 4 correlated with the clinical progression of CMV infection (odds ratio 1.74). In those patients who were treated with anti‐CMV therapy, a >97% reduction of the baseline viral load was associated with a complete therapeutic success. In conclusion, CMV infection is a highly dynamic process and the quantitation of CMV DNA by PCR is a powerful marker to control successfully the infection, but a strict follow‐up of the recipient and standardized PCR tests are mandatory for the best management of the infection. J. Med. Virol. 73:223–229, 2004. © 2004 Wiley‐Liss, Inc.
Variations in the serum concentrations of soluble Fas and soluble Fas ligand in Vietnamese patients infected with hepatitis B virus
Authors: Song Le H. , Binh Vu Q. , Duy Dinh N. , Bock Thomas C. , Kremsner Peter G. , Luty Adrian J.F. , Mavoungou Elie
Published: April 2004

Earlier studies of both chronic hepatitis B and C virus (HBV and HCV) patients have shown a strong correlation between the soluble membrane Fas (sFas) and Fas protein expression on hepatocytes. The serum concentrations of sFas and soluble Fas ligand (sFasL) was examined in both healthy and HBV‐infected Vietnamese patients to determine their relationship with the outcome of HBV infection. Patients with chronic rather than acute HBV had significantly higher amounts of sFas and sFasL, whilst the highest concentrations of both molecules were detected in those with malignant forms of HBV infection. sFas and sFasL concentrations tended to increase with a profile that paralleled the progression from asymptomatic to acute through chronic to malignant states, most markedly in the case of sFas. The sFas:sFasL ratio highlighted the relative predominance of sFas in those with acute and chronic HBV compared with asymptomatic or severe forms. In patients with hepatocellular carcinoma (HCC) a significant correlation was also observed between sFasL and alpha‐feto protein (AFP) levels. The results indicate that sFas and to a lesser extent sFasL levels are to some degree associated with clinical progression in HBV infection. J. Med. Virol. 73:244–249, 2004. © 2004 Wiley‐Liss, Inc.
Acute retinal necrosis six years after herpes simplex encephalitis: An elusive immune deficit suggested by insufficient test sensitivity
Authors: Preiser W. , Doerr H.W. , Buxbaum S. , Rabenau H.F. , Baatz H.
Published: April 2004

A patient presented with acute retinal necrosis of the left eye. Demonstration of herpes simplex virus (HSV) DNA in the aqueous humour confirmed the diagnosis. Negative results of HSV type‐specific antibody tests based on gG antigens suggested a primary HSV infection. However, the patient had a past history of laboratory‐confirmed herpes simplex encephalitis 6 years ago. Using antibody tests based on whole viral lysate antigens, he was seropositive from the onset, and immunoblot testing confirmed a lack of anti‐gG reactivity. To be able to assess whether this might be related to the apparent inability of his immune system to suppress clinically symptomatic HSV infection, serial samples were tested by an HSV neutralisation test and a whole‐blood flow cytometric assay to determine the frequency of HSV‐specific CD4 lymphocytes. However, this did not yield evidence of obvious immunodeficiency; the patient reacted similarly to known positive controls by both assays. Although type‐specific HSV serological tests based on gG are generally more specific than those based on whole viral lysate antigens, they have a somewhat lower sensitivity, as a certain percentage of HSV‐infected individuals do not develop antibodies against gG, and others may suffer a secondary loss of anti‐gG reactivity. Thus there is a risk of missing individual infected patients. Unless this potential problem is recognised, serious consequences might possibly result. We therefore urge virologists and clinicians to exercise great care if highly specific antibody assays based on recombinant proteins are employed. J. Med. Virol. 73:250–255, 2004. © 2004 Wiley‐Liss, Inc.
Vesicle transport in oligodendrocytes: Probable role of Rab40c protein
Authors: Rodriguez‐Gabin A.G. , Almazan G. , Larocca J.N.
Published: April 2004

Intracellular membrane trafficking plays an essential role in the structural and functional organization of oligodendrocytes, which synthesize a large amount of membrane to form myelin. Rab proteins are key components in intracellular vesicular transport. We cloned a novel Rab protein from an oligodendrocyte cDNA library, designating it Rab40c because of its homology with Rab40a and Rab40b. The DNA sequence of Rab40c shows an 843‐base pair open reading frame. The deduced amino acid sequence is a protein with 281 amino acids, with a molecular weight of 31,466 Da and an isoelectric point of 9.83. Rab40c presents a number of distinct structural features including a carboxyl terminal extension and amino acid substitutions in the consensus sequence of the GTP‐binding motifs. The carboxyl terminal region contains motifs that permit isoprenylation and palmitoylation. Binding studies indicate that Rab40c binds guanosine 5′‐0‐(3‐thiotriphosphate) (GTPγS) with a Kdof 21 μM and has a higher affinity for guanosine triphosphate (GTP) than for guanosine diphosphate (GDP). Rab40c is localized in the perinuclear recycling compartment, suggesting its involvement in endocytic events such as receptor recycling. The importance of this recycling in myelin formation is suggested by the increase in both Rab40c mRNA and Rab40c protein as oligodendrocytes differentiate. © 2004 Wiley‐Liss, Inc.
Towards oligoclusters – chemistry and properties
Authors: Humphrey Mark G.
Published: April 2004

The recent progress of the author's research group in the syntheses, electronic properties and optical properties of monomeric and oligomeric organotransition metal cluster‐containing systems is reviewed.
2D finite‐difference frequency‐domain method and its application for dispersion characteristic analysis of ferrite devices
Authors: Munir Achmad , Kubo Hiroshi , Sanada Atsushi , Awai Ikuo
Published: April 2004

In this paper, a two dimensional (2D) finite‐difference frequency‐domain (FDFD) method is applied to analyze the dispersion characteristics of ferrite devices. The FDFD formulation for ferrite devices is built from the integral form of Maxwell's equations. After implementing all the boundary conditions, the finite‐difference formulation is concluded as an eigen equation and then constructed by a highly sparse matrix. By solving the matrix‐eigen equation, the dispersion characteristics of ferrite devices for a given frequency can be obtained. In order to verify the validity of the proposed method, an infinite ferrite‐filled waveguide is examined and the numerical results are compared to both the theoretical result and the 3D finite‐difference time‐domain (FDTD) numerical result. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 437–439, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20163
Effects of weighting and damping coefficients on the accuracy of Higdon‐based absorbing boundary conditions
Authors: Wu Xin , Ramahi Omar M.
Published: April 2004

In this work, the effects of weighted difference schemes and damping factor on the spurious errors arising from the application of Higdon's absorbing boundary condition and the concurrent complementary operators method (C‐COM) are investigated. An optimized combination of the weighted difference scheme for boundary conditions and the damping term used to stabilize the boundary scheme are proposed to minimize the reflections. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 446–448, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20166
Design of dual‐band antenna for the ISM band using a backed microstrip line
Authors: Choi Seok H. , Park Jong K. , Kim Sun K. , Kim Hak S.
Published: April 2004

In this paper, we propose a new dual‐band antenna for applications of the ISM band. The proposed antenna is designed to operate at 2.4 and 5.8 GHz. The lower‐frequency band (2.4 GHz) can be obtained by using the meandering technique, and the upper‐frequency band (5.8 GHz) for dual‐band operation was achieved by embedding a backed microstrip line. Details of the proposed antenna design and experimental results are presented and discussed. The measured radiation patterns at 2.4 and 5.8 GHz and antenna gain across the respective frequency bands are also presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 457–460, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20170
An improved real‐frequency‐method technique for broadband matching of an HF antenna
Authors: Liu Yi‐Jun , Li Bin‐Hong , Chi Gao‐Ming
Published: April 2004

An improved real‐frequency method (RFM) technique which does not require any initial guess of the resistance excursions, is presented. According to the conjugate matching, the resistance excursions are obtained in least‐squares sense by a simpler process. A matching network is successfully synthesized to match an HF antenna well by using this improved technique. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 471–473, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20175
A dual‐band network of the feeding module utilized in diverse applications of a WLAN antenna
Authors: Wang Chien‐Jen , Tsai Wen‐Tsai
Published: April 2004

In this paper, a microstrip network of the feeding module used in diverse applications of an antenna for dual‐band wireless local‐area network (WLAN) operation is designed, fabricated, and measured. A wideband Wilkinson power divider with the defected‐ground structure (DGS) is integrated with a dual‐band SPDT switch module in order to provide two individual signal paths for the input of a two‐element antenna array. Two DGS slots are etched on the ground plane in order to reduce the loss of chip resistors, improve the impedance bandwidth, and enhance the efficiency of the output power. According to the simulated and measured results, the feeding module can be operated at the 2.4‐ and 5.2‐GHz bands. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 473–477, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20176
A dual‐mode uniplanar bandpass filter using an inset‐coupling structure
Authors: Görür Adnan , Çaliskan Şenol , Karpuz Ceyhun
Published: April 2004

A novel dual‐mode uniplanar square slot‐loop resonator, using an inset‐coupling mechanism with capacitive gaps is proposed. The mode splitting of the uniplanar resonator is described with respect to the perturbation size. A dual‐mode uniplanar filter using such a resonator is designed and fabricated with 5% bandwidth at the center frequency of 2.97 GHz for demonstration. The measured filter performance is presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 481–483, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20178
Rigorous full‐wave analysis of rectangular microstrip patches over ground planes with rectangular apertures in multilayered substrates that contain isotropic and uniaxial anisotropic materials
Authors: Fortaki T. , Benghalia A.
Published: April 2004

A rigorous full‐wave analysis of rectangular microstrip‐patch resonators over ground planes with rectangular apertures is presented. The rectangular patches, as well as the ground planes containing the rectangular apertures, are embedded in a multilayered substrate containing isotropic and/or uniaxial anisotropic materials. Using a matrix representation of each layer, the dyadic Green's functions of the problem are efficiently determined by the (TM, TE) representation. The validity of the solution is tested by comparing the computed results with the experimental data. Numerical results show that the rectangular apertures significantly affect the resonant frequencies of the rectangular microstrip patches. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 496–500, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20183
On the structure and packing of the moment matrix in problems supporting simultaneous electric and magnetic surface currents
Authors: Schoeman Marlize , Meyer Petrie
Published: April 2004

An efficient packing algorithm is presented for filling the method of moments (MoM) matrix in problems containing both electric and magnetic currents, and multiple coupled regions separated by infinite conducting ground planes. Provision is made for symmetric and unsymmetrical submatrices. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 500–505, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20184
A novel microstrip bandpass filter
Authors: Jianxin Chen , Mengxia Yu , Jun Xu , Quan Xue
Published: April 2004

A novel compact microstrip bandpass filter which is realized by combining new slow‐wave effect with dual‐parallel coupling, is proposed. The filter is not only compact in size, but also has low insertion loss and sharp rejection. A demonstration filter is optimally designed and fabricated. Theoretical and experimental results are presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 505–506, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20185
Improvement in breast lesion characterization with dynamic contrast‐enhanced MRI using pharmacokinetic modeling and bookend T1 measurements
Authors: Cron Greg O. , Kelcz Frederick , Santyr Giles E.
Published: April 2004

Dynamic contrast‐enhanced breast MR imaging was performed on 14 patients (five cancerous lesions, nine benign) with slice‐selective spoiled gradient‐recalled echo (2D SPGR) imaging. Adiabatic saturation recovery T1 measurements were performed before (T1pre) and after (T1post) 2D SPGR imaging. These two “bookend” T1 measurements were used to calibrate the equations which were employed to convert the time course of the 2D SPGR signal strength to T1‐vs.‐time, which in turn was used to compute the gadolinium concentration‐vs.‐time ([C](t)) in the lesion. The extraction‐flow product (EF) was computed for each lesion by pharmacokinetic modeling of [C](t). For this study, EF provided a sensitivity and specificity for cancer of 100% and 78%, respectively. When only T1pre was used to estimate [C](t) (which assumes a priori knowledge of the shape and amplitude of the slice profile), the sensitivity and specificity fell to 80% and 56%, respectively. This is presumably due to unexpected variations in the shape and/or amplitude of the slice profile, which could be caused by factors such as patient‐to‐patient variations in breast geometry or inconsistently set transmit gains. Therefore, both T1pre and T1post measurements are necessary for optimum sensitivity and specificity using pharmacokinetic analysis. Magn Reson Med 51:1066–1070, 2004. © 2004 Wiley‐Liss, Inc.
Effects of, and corrections for, cross‐term interactions in q‐space MRI
Authors: Brihuega‐Moreno Oscar , Heese Frank P. , Tejos Cristián , Hall Laurance D.
Published: April 2004

The present study assesses the effects of cross‐term interactions between diffusion and imaging gradients in magnetic resonance imaging q‐space analysis, and corrects for those effects for both spin echo and stimulated echo diffusion‐weighted sequences. These corrections are demonstrated experimentally in unrestricted media for water and theoretically by simulating the case of restricted diffusion in a sphere. By correcting for the cross‐term interactions, large imaging gradients can be used without compromising the results. Ignoring cross‐term interactions could lead to a misunderstanding of the q‐space analysis; for instance, the microstructural size of the sample could be overestimated, or isotropic media could be misinterpreted as being anisotropic. Magn Reson Med 51:1048–1054, 2004. © 2004 Wiley‐Liss, Inc.
Analysis of multiple‐acquisition SSFP
Authors: Bangerter Neal K. , Hargreaves Brian A. , Vasanawala Shreyas S. , Pauly John M. , Gold Garry E. , Nishimura Dwight G.
Published: April 2004

Refocused steady‐state free precession (SSFP) is limited by its high sensitivity to local field variation, particularly at high field strengths or the long repetition times (TRs) necessary for high resolution. Several methods have been proposed to reduce SSFP banding artifact by combining multiple phase‐cycled SSFP acquisitions, each differing in how individual signal magnitudes and phases are combined. These include maximum‐intensity SSFP (MI‐SSFP) and complex‐sum SSFP (CS‐SSFP). The reduction in SSFP banding is accompanied by a loss in signal‐to‐noise ratio (SNR) efficiency. In this work a general framework for analyzing banding artifact reduction, contrast, and SNR of any multiple‐acquisition SSFP combination method is presented. A new sum‐of‐squares method is proposed, and a comparison is performed between each of the combination schemes. The sum‐of‐squares SSFP technique (SOS‐SSFP) delivers both robust banding artifact reduction and higher SNR efficiency than other multiple‐acquisition techniques, while preserving SSFP contrast. Magn Reson Med 51:1038–1047, 2004. © 2004 Wiley‐Liss, Inc.
Estimation of the differential pressure at renal artery stenoses
Authors: Yim Peter J. , Cebral Juan R. , Weaver Ashley , Lutz Robert J. , Soto Orlando , Vasbinder G. Boudewijn C. , Ho Vincent B. , Choyke Peter L.
Published: April 2004

Atherosclerotic disease of the renal artery can lead to reduction in arterial caliber and ultimately to conditions including renovascular hypertension. Renal artery stenosis is conventionally assessed, using angiography, according to the severity of the stenosis. However, the severity of a stenosis is not a reliable indicator of functional significance, or associated differential pressure, of a stenosis. A methodology is proposed for estimation of the renal artery differential pressure (RADP) from MR imaging. Realistic computational fluid dynamics (CFD) models are constructed from MR angiography (MRA) and phase‐contrast (PC) MR. The CFD model is constructed in a semiautomated manner from the MR images using the Isosurface Deformable Model (IDM) for surface reconstruction and a Marching Front algorithm for construction of the volumetric CFD mesh. Validation of RADP estimation was performed in a realistic physical flow‐through model. Under steady flow, the CFD estimate of the differential pressure across a stenosis in the physical flow‐through model differed by an average of 5.5 mmHg from transducer measurements of the pressure differential, for differential pressures less than 60 mmHg. These results demonstrate that accurate estimates of differential pressure at stenoses may be possible based only on structural and flow images. Magn Reson Med 51:969–977, 2004. Published 2004 Wiley‐Liss, Inc.
The effect of low‐temperature crystallization on the mechanical behavior of rubber
Authors: Fuller K.N.G. , Gough J. , Thomas A.G.
Published: April 2004

In cold climates the correct performance of rubber components such as seismic isolators depends on them maintaining their elastic properties when exposed to prolonged periods at low temperatures. The high damping compounds developed for seismic isolation are normally especially prone to crystallization when exposed to subzero temperatures for periods of a few weeks. The effect of low‐temperature crystallization on the mechanical stiffening of natural rubber is evaluated. The relationship between the shear modulus and amount of crystallization is measured using a technique in which the dimensional change and stiffness are monitored simultaneously. The relationship is found to be approximately independent of the crosslink density and the temperature of crystallization. It appears not to be realistically modeled by considering the crystals to behave as rigid filler particles but good qualitative agreement with experiment was obtained by modeling the crystals as a network of threads. Partially crystalline rubbers are found to yield under the application of a large stress like other partially crystalline polymers. Mechanisms for suppressing crystallization in rubber are discussed and the low‐temperature stiffening of specially formulated rubber compounds for seismic isolation is presented. These results show that carefully formulated high damping natural rubber compounds can give adequate performance at low temperatures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2181–2190, 2004
Psychosocial problems among younger women with breast cancer
Authors: Avis Nancy E. , Crawford Sybil , Manuel Janeen
Published: April 2004

Women diagnosed with breast cancer at a younger age often have concerns less frequently faced by older women. A cross‐sectional survey of 204 women diagnosed with breast cancer at age 50 or younger within the past 3.5 years was conducted to examine issues particularly faced by younger women. The questionnaire included standardized measures of problems related to breast cancer (CARES) and open‐ended questions asking women about their experiences. Concerns about premature menopause and pregnancy related issues, among those women for whom these issues were applicable, had the highest ratings as problems experienced by women since their diagnosis. Among all women, sexual functioning was a greater problem than lack of sexual interest, and body image was of moderate concern. Overall, relationships with partners were not a problem. In multivariate analyses, having a mastectomy was associated with greater problems with body image and interest in sex. Chemotherapy was associated with greater sexual dysfunction. Responses to open‐ended questions were particularly informative and reflected the diversity of responses women have to breast cancer. Findings reinforce the need to develop interventions to help women deal with premature menopause and problems with sexual functioning following chemotherapy. Copyright © 2003 John Wiley & Sons, Ltd.
We are talking, but are they listening? Communication patterns in families with a history of breast/ovarian cancer (HBOC)
Authors: Kenen Regina , Arden‐Jones Audrey , Eeles Rosalind
Published: April 2004

This study explores how family communication patterns and family scripts influence the dissemination of genetic information and the sharing of feelings about genetic inheritance in families of healthy women who have attended a cancer genetics risk clinic because of their family history of breast and, or ovarian cancer. Family scripts are sets of expectations, beliefs, and norms that assign meaning to patterns of interaction, connect generations and provide guidance for action. We conducted an exploratory, qualitative study at a major clinical and research cancer center in the United Kingdom from January through June 2000 approved by the hospital clinical research and ethics committees. Twenty‐one semi‐structured, in‐depth interviews were conducted using a purposive sample of women coming to the cancer genetics risk clinic for the first time, supplemented by 5 months of participant observation. We identified several communication patterns: open and supportive; directly blocked, indirectly blocked, self‐censored and use of third parties. Some family members shared their feelings and discussed ways of trying to avoid developing breast or ovarian cancer; for others disseminating information or just talking about inherited susceptibility for breast and, or ovarian cancer fell into the script violation category; still others tried to renegotiate their family scripts. Copyright © 2003 John Wiley & Sons, Ltd.
Functional assessment of “in vivo” and “in silico” mutations in the guanine binding site of RNase T1: A DFT study
Authors: Mignon Pierre , Loverix Stefan , Steyaert Jan , Geerlings Paul
Published: April 2004

Experimentally, the functional assessment of amino acid side chains in proteins is carried out by comparing parameters such as binding constants for the wild‐type protein and a mutant protein in which the considered side chain is deleted. In the present study, we apply a density functional theory (DFT) methodology to obtain changes in binding energy upon mutations in the enzyme ribonuclease T1. Mutant structures were either taken directly from crystallographic data (“in vivo”) allowing for conformational changes upon mutation, or derived from the wild‐type (“in silico”). Excluding entropic contributions, the computed interaction energy changes upon mutation in vivo correlate qualitatively well with experimental binding free energy changes. In contrast, the in silico approach does not perform as well, especially for residues that contribute largely to binding. Subsequently, we assessed the applicability of the in vivo approach by analyzing the functional cooperativity between pairs of side chains. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Test of treatment effect in pre‐drug and post‐drug count data with zero‐inflation
Authors: Paul Sudhir. R. , Jiang Xing , Rai Shesh Nath , Balasooriya Uditha
Published: April 2004

A procedure for testing for treatment effect in data similar to the data on premature ventricular contractions (PVC) is presented. We consider a zero‐inflated beta‐binomial model. Based on this model, we develop score tests to test for treatment effect in the data in which observations in the form of counts are recorded before and after applying a therapy. Results of a small simulation experiment, to study small sample behaviour of a score test and a likelihood ratio test, are reported and the PVC data are analysed. Both the score and the likelihood ratio tests show good level properties. Either the score tests or the likelihood ratio tests can be used for testing the presence of treatment effect. The score tests, however, may be preferable because they use estimates of the parameters only under the null hypothesis and in the important range π<0.5 power of the score test statistic S1 is slightly better than the likelihood ratio statistic LR1. Copyright © 2004 John Wiley & Sons, Ltd.
Determination of gold, platinum and uranium in South African ores by high‐energy XRF spectrometry
Authors: Robertson M. E. A. , Feather C. E.
Published: April 2004

An automated energy‐dispersive x‐ray fluorescence spectrometer, called the AZTEC, was developed for the non‐destructive determination of gold, platinum and uranium in Witwatersrand ores, by utilizing the high‐energy spectral regions of the K x‐ray lines of these elements. It provides a viable alternative to fire assay, and measures gold concentrations down to <1 ppm. About 100 g of pulverized sample are presented for analysis in a 20 mm diameter tube, and the fluorescent x‐rays are detected by an array of up to 12 high‐purity germanium detectors. Count‐rates of up to 106 counts per second per detector can be processed by the signal processing electronics. The AZTEC technique is a variant of the scattered radiation technique. Concentration is related to peak intensities corrected for background, matrix variations, density and line overlaps. Provided that the samples are finely pulverised, the AZTEC analyses compare well with those obtained by fire assay. Production instruments are being used mainly in the gold mining industry, where they have analysed over 107 samples to date. Copyright © 2004 John Wiley & Sons, Ltd.
Asymptotic analysis of the Riemann problem for constant coefficient hyperbolic systems with relaxation
Authors: Hittinger J.A.F. , Roe P.L.
Published: April 2004

The discontinuous Riemann initial value problem is considered for dissipative, constant coefficient hyperbolic systems with relaxation source terms. A short‐time asymptotic expansion, a specialization of the results of Le Floch and Raviart [11], is constructed for the general linear system. Exact rates for the decay of the initial discontinuities are found to be in agreement with recent results from other approaches. A multiple scales analysis is used to identify the long‐time asymptotic behavior. Many of the results can be exemplified in a simple model problem for which the exact solution can be found.
Duration-constrained regular expressions
Authors: Xuandong Li , Jianhua Zhao , Tao Zheng , Yong Li , Guoliang Zheng
Published: April 2004

This paper investigates the logic-automata-connection for Duration Calculus. It has been frequently observed that Duration Calculus with linear duration terms comes close to being a logic of linear hybrid automata. We attempt to make this relation precise by constructing Kleene-connection between
duration-constrained regular expressions
and a subclass of linear hybrid automata called
loop-reset automata
in which any variable tested in a loop is reset in the same loop. The formalism of duration-constrained regular expressions is an extension of regular expressions with duration constraints, which are essentially formulas of Duration Calculus without negation, yet extended by a Kleene-star operator. In this paper, we show that this formalism is equivalent in expressive power to loop-reset automata by providing a translation procedure from expressions to automata and vice verse.
Performance analysis of probabilistic action systems
Authors: Hallerstede Stefan , Butler Michael
Published: April 2004

Formal notations like B or action systems support a notion of refinement. Refinement relates an abstract specification
A
to a concrete specification
C
that is as least as deterministic. Knowing
A
and
C
one proves that
C
refines, or implements, specification
A
. In this study we consider specification
A
as given and concern ourselves with a way to find a good candidate for implementation
C
. To this end we classify all implementations of an abstract specification according to their performance. We distinguish performance from correctness. Concrete systems that do not meet the abstract specification correctly are excluded. Only the remaining correct implementations
C
are considered with respect to their performance. A good implementation of a specification is identified by having some optimal behaviour in common with it. In other words, a good refinement corresponds to a reduction of non-optimal behaviour. This also means that the abstract specification sets a boundary for the performance of any implementation. We introduce the probabilistic action system formalism which combines refinement with performance. In our current study we measure performance in terms of long-run expected average-cost. Performance is expressed by means of probability and expected costs. Probability is needed to express uncertainty present in physical environments. Expected costs express physical or abstract quantities that describe a system. They encode the performance objective. The behaviour of probabilistic action systems is described by traces of expected costs. A corresponding notion of refinement and simulation-based proof rules are introduced. Probabilistic action systems are based on discrete-time Markov decision processes. Numerical methods solving the optimisation problems posed by Markov decision processes are well-known, and used in a software tool that we have developed. The tool computes an optimal behaviour of a specification
A
thus assisting in the search for a good implementation
C
.
Extratympanic Electrocochleographic Changes on Noise‐Induced Temporary Threshold Shift
Authors: Nam Eui‐Cheol , Won Jun Yeon
Published: April 2004

OBJECTIVE

Electrocochleography (ECoG) is a sensitive evoked‐response test for evaluating changes in cochlear function. We investigated the extratympanic ECoG in a noise‐induced temporary threshold shift (TTS) to evaluate the usefulness of ECoG in the early detection of noise‐induced hearing loss (NIHL).

STUDY DESIGN AND METHODS

In a prospective analysis, 15 healthy ears were exposed to 90.3‐ to 105.0‐dB noise for 3 hours in the same computer‐game arcade. Pure‐tone audiometry and ECoG were performed before, immediately after, and 24 hours after the exposure.

RESULTS

Before the exposure, the average hearing level was 5.8 ± 2.7 dB, which increased significantly to 12.8 ± 2.8 dB immediately after exposure. A marked increment in the SP/AP (summating potential/action potential) ratio was observed with the TTS. The mean ratio was 0.22 ± 0.11 before the exposure, 0.46 ± 0.18 in the TTS phase, and 0.20 ± 0.11 after resolution.

CONCLUSION

The results of this study suggest that the SP/AP ratio is useful for the early detection and monitoring of NIHL. (Otolaryngol Head Neck Surg 2004;130:437–42.)
Cerebrospinal Fluid Pressure Monitoring after Repair of Cerebrospinal Fluid Leaks
Authors: Schlosser Rodney J. , Wilensky Eileen Maloney , Grady M. Sean , Palmer James N. , Kennedy David W. , Bolger William E.
Published: April 2004

OBJECTIVE

To measure intracranial pressures (ICPs) via lumbar drains after surgical repair of cerebrospinal fluid (CSF) leaks.

METHODS

We conducted a retrospective review of ICP measurements through lumbar drains during the immediate postoperative period after CSF leak repair.

RESULTS

Eight patients with spontaneous CSF leaks underwent surgery and postoperative CSF pressures were measured via lumbar drains. ICP was elevated in 7/8 patients (mean, 32.5 cm H2O). Diuretics reduced ICP (mean, 10 cm H2O). Three traumatic CSF leaks patients served as controls (mean, ICP 14 cm H2O).

CONCLUSION

Measurement of ICP through lumbar drains provides important information regarding the pathophysiology of CSF leaks that has an impact on subsequent medical and surgical treatment. Although the precise cause and mechanism of spontaneous CSF leaks are not fully understood, this study indicates that elevated ICP plays a role and that further medical or surgical treatment to correct the intracranial hypertension may be warranted. (Otolaryngol Head Neck Surg 2004;130:443‐8.)
Decreased Ataxia and Improved Balance after Vestibular Rehabilitation
Authors: Cohen Helen S. , Kimball Kay T.
Published: April 2004

OBJECTIVES

To determine the effects of vestibular rehabilitation on gait ataxia and balance.

SETTING

Tertiary care center.

STUDY DESIGN

Subjects were patients with chronic vertigo due to peripheral vestibular impairments, referred for vestibular rehabilitation. They were assessed on the Timed Up and Go test, ataxia during a path integration test, computerized dynamic posturography, level of vertigo, independence in activities of daily living, and psychological locus of control. They were randomly assigned to three home program treatment groups.

RESULTS

Ataxia decreased significantly, and posturography scores and time to perform Timed Up and Go improved significantly, for all subjects. Improvements were significantly related to scores on the ambulation subtest of the Vestibular Disorders Activities of Daily Living Scale, decreases in vertigo, and increases in locus of control.

CONCLUSIONS

For many patients, a simple home program of vestibular habituation head movement exercises is related to reduced symptoms of imbalance during stance and gait. (Otolaryngol Head Neck Surg 2004;130:418–25.)
Determining habitat suitability for soil invertebrates in an extreme environment: the McMurdo Dry Valleys, Antarctica
Authors: Courtright Ericha M. , Wall Diana H. , Virginia Ross A.
Published: April 2004

We sampled soils in the McMurdo Dry Valleys to determine the habitats that were suitable for extreme for soil invertebrates. Suitability was assessed by comparing nematode species diversity and abundance, and tardigrade and rotifer abundance as related to soil properties at three spatial scales: landscape (across Taylor, Wright and Victoria valleys), at three distant locations within valleys, and within small plots (1 m2). Extreme environments were characterized by the lack of nematode abundance and diversity, high salinity, low soil moisture and organic carbon, and higher elevation or a geographic location less accessible for dispersing organisms. Suitable habitats were more frequent near the coast and at lower elevations. Extreme habitats could be defined based on one environmental factor, but more typically a set of interrelated soil and environmental factors appear to determine the abundance and composition of the soil community. The three Dry Valley nematode species occupied distinct regions of a multivariate biplot relating soil chemistry and moisture. Scottnema lindsayae is unusual for its ability to live in a wide range of extreme soil habitats. Our research shows that in the McMurdo Dry Valleys, life flourishes in suitable soil habitats and that extreme habitats (“no invertebrates”) can be defined.
Geomorphological sketch map of the Fossil Bluff area (Alexander Island, Antarctica) mapped from aerial photographs
Authors: Salvatore Maria Cristina
Published: April 2004

A geomorphological sketch map of the Fossil Bluff area, showing the main morphological characteristics was prepared from aerial photographs taken by the British Antarctic Survey in 1995. Landforms and deposits mapped include those related to glaciers and the local hydrography, periglacial and nival activity, and wind and gravity action. Data mapped originally at a scale of 1:12 500 and simplified for presentation here at a scale of about 1:30 000, have been digitized as vectors using a GIS. In this way these data may easily be integrated with other environmental data for future research.
The Pagodroma Group – a Cenozoic record of the East Antarctic ice sheet in the northern Prince Charles Mountains
Authors: McKelvey B.C. , Hambrey M.J. , Harwood D.M. , Mabin M.C.G. , Webb P.-N. , Whitehead J.M.
Published: April 2004

The northern Prince Charles Mountains overlook the western side of the 700 km long Lambert Glacier–Amery Ice Shelf drainage system. Within these mountains, at Amery Oasis (70°50′S, 68°00′E) and Fisher Massif (71°31′S, 67°40′E), the Cenozoic glaciomarine Pagodroma Group consists of four uplifted Miocene and Pliocene–early Pleistocene formations here named the Mount Johnston, Fisher Bench, Battye Glacier and Bardin Bluffs formations. These are composed of massive and stratified diamicts, boulder gravels and minor laminated sandstones, siltstones and mudstones. Each formation rests on either Precambrian metamorphic rocks, or on Permo-Triassic fluvial strata. The unconformity surfaces are parts of the walls and floors of palaeofjords. The Miocene Fisher Bench Formation exceeds 350 m in thickness at Fisher Massif, where the yet older Miocene (or Oligocene) Mount Johnston Formation overlies basement rocks at up to 1400 m above sea level. Individual formations contain either Miocene diatoms, or else Pliocene–early Pleistocene diatom-foram assemblages. The diamicts are interpreted as fjordal ice-proximal or ice-contact sediments, deposited seawards of tidewater glacier fronts located some 250 to 300 km inland of the present ocean margin. Each formation records an ice recession following a glacial expansion.