Improving accuracy by subpixel smoothing in the finite-difference time domain

Finite-difference time-domain (FDTD) methods suffer from reduced accuracy when modeling discontinuous dielectric materials, due to the inhererent discretization (pixelization). We show that accuracy can be significantly improved by using a subpixel smoothing of the dielectric function, but only if the smoothing scheme is properly designed. We develop such a scheme based on a simple criterion taken from perturbation theory and compare it with other published FDTD smoothing methods. In addition to consistently achieving the smallest errors, our scheme is the only one that attains quadratic convergence with resolution for arbitrarily sloped interfaces. Finally, we discuss additional difficulties that arise for sharp dielectric corners.

[MM1 variant of sporadic Creutzfeldt-Jakob disease with long duration akinetic mutism state]

INTRODUCTION

When patients present with a characteristic clinical picture of Creutzfeldt-Jakob disease (CJD) associated with positive 14-3-3 assay, periodic sharp wave complexes, high-signal of the striatum on magnetic resonance imaging, and homozygosis methionine (M) in codon 129, the median survival is 4 to 6 months.

CLINICAL CASE

We report a 58-year-old woman with these typical features who survived 21 months, 19 of them in an akinetic mutism state. The autopsy confirmed the diagnosis of the most common CJD phenotype (MM1), usually associated with a shorter survival, and demyleinitation of the white matter (panencephalopathic form).

CONCLUSIONS

The MM1 variant of CJD, with a rapidly progressive course leading into an akinetic mutism shortly after disease onset can be followed by a long akinetic mutism state. This profile is suggestive of panencephalopathic form and should be taken into account when counselling about survival.

Risk factors for asthma and allergy associated with urban migration: background and methodology of a cross-sectional study in Afro-Ecuadorian school children in Northeastern Ecuador (Esmeraldas-SCAALA Study)

Background

Asthma and allergic diseases are becoming increasingly frequent in children in urban centres of Latin America although the prevalence of allergic disease is still low in rural areas. Understanding better why the prevalence of asthma is greater in urban migrant populations and the role of risk factors such as life style and environmental exposures, may be key to understand what is behind this trend.

Methods/design

The Esmeraldas-SCAALA (Social Changes, Asthma and Allergy in Latin America) study consists of cross-sectional and nested case-control studies of school children in rural and urban areas of Esmeraldas Province in Ecuador. The cross-sectional study will investigate risk factors for atopy and allergic disease in rural and migrant urban Afro-Ecuadorian school children and the nested case-control study will examine environmental, biologic and social risk factors for asthma among asthma cases and non-asthmatic controls from the cross-sectional study. Data will be collected through standardised questionnaires, skin prick testing to relevant aeroallergen extracts, stool examinations for parasites, blood sampling (for measurement of IgE, interleukins and other immunological parameters), anthropometric measurements for assessment of nutritional status, exercise testing for assessment of exercise-induced bronchospasm and dust sampling for measurement of household endotoxin and allergen levels.

Discussion

The information will be used to identify the factors associated with an increased risk of asthma and allergies in migrant and urbanizing populations, to improve the understanding of the causes of the increase in asthma prevalence and to identify potentially modifiable factors to inform the design of prevention programmes to reduce the risk of allergy in urban populations in Latin America.

Impact of antibiotic guideline compliance on duration of mechanical ventilation in critically ill patients with community-acquired pneumonia

OBJECTIVE

Multiple guidelines exist to aid clinicians in choosing antibiotics to treat patients with severe community-acquired pneumonia (SCAP). Our goal was to assess the impact of following these guidelines, such as those from the Infectious Disease Society of America (IDSA), on the duration of mechanical ventilation (MV).

DESIGN

Analysis of a prospective registry.

SETTING

Multiple ICUs in Spain.

PATIENTS

ICU patients with SCAP requiring > or = 24 h of endotracheal intubation and surviving their ICU course.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographics, comorbid diseases, severity of illness, and process of care variables were recorded. The duration of MV in patients receiving an antibiotic regimen consistent with IDSA guidelines was compared to patients with prescriptions not in accordance with IDSA recommendations. In the cohort (n = 199), Streptococcus pneumoniae was the most frequent pathogen, and unadjusted analysis showed that the duration of MV was longer in persons receiving IDSA-noncompliant regimens (11 days vs 10 days). In a multivariate hazard model, two variables were independently associated with greater durations of MV: development of acute renal failure (hazard ratio, 1.47; 95% confidence interval [CI], 1.02 to 2.12), and prescription of an IDSA-noncompliant regimen (hazard ratio, 1.40; 95% CI, 1.02 to 1.93). Adjusted analysis indicated that patients receiving treatment that was not compliant with IDSA guidelines received MV an added 3 days.

CONCLUSION

Failure to follow antibiotic recommendations for the treatment of SCAP may increase the need for continuing MV. Conversely, guideline compliance could represent a surrogate marker that captures other aspects of clinical care, rather than be the direct factor leading to better outcomes. Nonetheless, given the costs associated with MV, enhanced guideline compliance may represent a means for improving outcomes and enhancing resource utilization.

Refinement of the mouse model of congenital toxoplasmosis

The goals of the present investigation, focusing on the BALB/c mouse model of congenital toxoplasmosis, were: (1) to find a method to determine pregnancy in the mouse. The method has 100% sensitivity and 72% specificity; (2) to test congenital transmission during the chronic stage of toxoplasmosis. This occurred in 2 of 10 mice tested; (3) to investigate the relationship between the infective dose and the rate of congenital transmission. This was not demonstrated for doses of 10(2) to 10(3) bradyzoites and oocysts of Prugniaud, M3 and M7741 strains, with transmission rates of 3 of 8 to 6 of 10 mice inoculated; (4) to determine homologous and heterologous protection. Homologous protection was demonstrated with Prugniaud cysts, and heterologous protection was found between ME-49 and M3 cysts. This finding is consistent with the uniform natural protection against congenital toxoplasmosis seen in immune women and ewes.

Imaging for evaluation of suspected cervical spine trauma: a 2-year analysis

OBJECTIVE

To examine the role of radiography in screening trauma patients with suspected injury to the cervical spine.

SUBJECTS AND METHODS

Over a period of 2 years, 5172 people were admitted to our trauma service and 297 (5.4%) were found to have cervical fractures. The radiographic and CT films and reports of 245 of these 297 patients were reviewed.

RESULTS

The 245 subjects had sustained 309 distinct individual injuries. Radiography detected injuries in 108 cases (44.1%) and CT detected injuries in 243 cases (99.2%). The two fractures missed by CT occurred at C2; one fracture was obscured by dental artefacts and the other was in the horizontal plane of the scan. Both fractures were detected on lateral radiographs of the region.

CONCLUSION

CT is superior to radiography for identification of cervical spine fractures. The fractures most likely to be missed by CT occur at C2. We recommend that CT be used as the primary screening method for people with suspected cervical injury, together with a single lateral view of the cervical spine to include the C2 region.

Selection of induction chemotherapy (CT) in esophageal and gastroesophageal junction cancer by positron emission tomography (PET)

14041

Background: Preoperative CT improves survival in esophageal cancer. 50% of patients (pts) do not respond to cisplatin+5-FU (C+F). The reduction of fluorodeoxyglucose uptake after 14 days (d) of CT predicts clinical response (rsp). Our objective was to measure the rsp (rsp) rate after CT adjusted according to PET rsp. Methods: Eligible pts were ≥ stage II esophageal cancer and able to tolerate CT. By adjusting CT according to PET rsp, we expected an increase of rsp rate by 25%. Taking into account a confidence level of 90%, an error β of 20% and a minimal error of 15% (even with such a high error rate the data will exceed the standard results), we calculated a sample size of 23 pts. All underwent esophagoscopy, computed tomography and PET scan prior to C (100mg/m2 d1) +5-FU (1,000mg/m2 d1–5). If PET rsp after first cycle (uptake decreased ≥ 35%), we continued up to third C+F cycle, then if endoscopy rsp: C+F + concurrent radiation only if stage II or III. If no endoscopy rsp, surgery only if stage II or III. On the other hand, if the pts had no rsp in PET after first C+F cycle they continued with 2 cycles of docetaxel (35mg/m2 d 1 & 8) and irinotecan (50mg/m2 d 1 & 8) (D+I) every 21 d and then if endoscopy rsp: radiation + docetaxel only if stage II or III. If no endoscopy rsp, surgery. Results: Since 2/04, 23 pts have been enrolled. Location: 2 cervical, 4 upper thoracic, 7 mid-thoracic, 10 GE junction. PET stage: 7 IIA, 6 IIB, 2 III, 2 IVA, 6 IVB. Up-staging with PET in 6 pts, down-staging in 4 pts. Histology: 10 Adenocarcinoma, 13 squamous carcinoma. Improved swallowing function: from a total of 12 PET responders, 9 had a clinical rsp after C+F, 3 did not. From 11 PET non-responders, 7 had a clinical rsp after D+I, 4 did not. Global clinical rsp = 16/23 (70%). Endoscopy rsp (frequent inaccuracy by overstaging): from a total of 12 PET responders, 6 had a clinical rsp after C+F, 6 did not. From 11 PET non-responders, 7 had a clinical rsp after D+I, 4 did not. Global clinical rsp = 13/23 (57%). Conclusion: Our results suggest that it is possible to significantly increase the percentage of pts who respond to induction CT adjusted according to PET in esophagogastric cancer before concurrent chemoradiotherapy or esophagectomy, or both.

No significant financial relationships to disclose.

Implications of COPD in patients admitted to the intensive care unit by community-acquired pneumonia

The mortality rate of chronic obstructive pulmonary disease (COPD) patients with community-acquired pneumonia (CAP) is reported to be low. However, studies carried out to date have included <20% of critically ill patients. The current authors performed a secondary analysis of a prospective study evaluating 428 immunocompetent patients admitted to the intensive care unit (ICU) for severe CAP. In total, 176 COPD patients were compared with 252 non-COPD patients. In COPD patients, ICU mortality (odds ratio (OR) 1.58; 95% confidence interval (CI) 1.01-1.43) and mechanical ventilation (OR 2.78; 95% CI 1.63-4.74) rates were higher than in non-COPD patients. The ICU mortality was 39% for COPD patients initially intubated and 50% for those who failed noninvasive ventilation. The proportion of patients who were males, aged >/=70 yrs, smokers and who had chronic heart disease or Pseudomonas aeruginosa were higher in COPD patients. Inappropriate empirical antibiotic therapy was associated with higher mortality (OR 3.8; 95% CI 1.19-12.6). ICU mortality in COPD patients with adequate therapy was associated with bilateral pneumonia (OR 2.32; 95% CI 1.18-4.53) and shock (OR 3.53; 95% CI 1.31-9.71). In conclusion, chronic obstructive pulmonary disease patients hospitalised with community-acquired pneumonia in the intensive care unit had higher mortality and need of mechanical ventilation when compared with patients without chronic obstructive pulmonary disease.

Improved search for nu(mu) --> nu(e) oscillation in a long-baseline accelerator experiment

We performed an improved search for nu(mu) --> nu(e) oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2 x 10(19) protons on target. No evidence for a nu(e) appearance signal was found, and we set bounds on the nu(mu) --> nu(e) oscillation parameters. At Deltam(2)=2.8 x 10(-3) eV(2), the best-fit value of the K2Knu(mu) disappearance analysis, we set an upper limit of sin(2)2theta(mue) < 0.13 at a 90% confidence level.

Gene chromosomal organization and expression in cultured human neurons exposed to cocaine and HIV-1 proteins gp120 and tat: drug abuse and NeuroAIDS

As a model for Neuropsychiatric dysfunction in NeuroAIDS due to HIV-1 infection and drug abuse, we analyzed gene expression in human neurons treated with cocaine and HIV-1 proteins tat and envelope (env). One-way ANOVA showed statistically significant genes among the treatment groups (p < or = 0.0005). The identified genes were then subjected to a "stepwise" analysis using a repeated measures ANOVA to discover genes with parallel response group profiles across the treatment conditions. These groups were then analyzed using a repeated measures ANOVA to assess treatment main effects and gene-by-treatment interactions within groups. One-way ANOVA produced 35 genes that were significantly associated across all treatment conditions. Factorial analysis of each gene found statistically significant differences: 30--tat, 17--cocaine, 10--env, 6--tat/env, 6--coc/env, and 4--coc/tat. Analyses across genes found three sets of four genes, one set of three genes, and three sets of two genes with parallel profiles. Identified genes had functions included signaling, immune related, and transcription control. The genes were not stochastically arranged on the chromosomes, were in proximity to each other, and to other genes involved in neuropsychiatric diseases. We hypothesize that these genes fall in transcriptionally isolated groups and that abused drugs and HIV-1 proteins trigger transcription overload, coerced expression that may result in damage to the chromosome's control and organization of chromatin transcription machinery.

Surface-emitting fiber lasers

All fiber lasers to date emit radiation only along the fiber axis. Here a fiber that exhibits laser emission that is radially directed from its circumferential surface is demonstrated. A unique and controlled azimuthally anisotropic optical wave front results from the interplay between a cylindrical photonic bandgap fiber resonator, anisotropic organic dye gain, and a linearly polarized axial pump. Low threshold (86nJ) lasing at nine different wavelengths is demonstrated throughout the visible and near-infrared spectra. We also report the experimental realization of unprecedented layer thicknesses of 29.5 nm maintained throughout meter-long fibers. Such a device may have interesting medical applications ranging from photodynamic therapy to in vivo molecular imaging, as well as textile fabric displays.

Cellular immune response to pulmonary infections in HIV-infected individuals hospitalized with diverse grades of immunosuppression

The lymphocyte profile of 521 HIV-infected subjects hospitalized at Jackson Memorial (2001-2002) was compared across main respiratory diseases. Study data included medical history and all laboratory evaluations performed during hospitalization. Community-acquired pneumonias (CAP, 52%), Pneumocystis jiroveci pneumonia (PCP, 24%), tuberculosis (TB, 9%) and non-tuberculous mycobacterial diseases (NTM, 12%) were the most frequent causes of admission. Patients hospitalized with PCP and NTM exhibited the lowest CD4 counts (P=0.003). PCP patients had the highest B-cell percentages (P=0.04). CAP patients had the highest CD8 and CD4 percentages and the lowest percentage of Natural Killer (NK) cells and viral burdens. TB patients exhibited the lowest NK-cell (11.4+/-6.3) and B-cell percentages (13.6+/-12) and the highest CD8 (59+/-14) percentage. NTM patients, in contrast, had the highest NK-cell percentages of the groups (19.1+/-11.6, P=0.01). Additionally, immune responses associated with respiratory pathogens differed in HIV-infected patients with CD4(+) cells above and below 200 counts.

New techniques for imaging, digitization and analysis of three-dimensional neural morphology on multiple scales

Cognitive impairment in normal aging and neurodegenerative diseases is accompanied by altered morphologies on multiple scales. Understanding of the role of these structural changes in producing functional deficits in brain aging and neuropsychiatric disorders requires accurate three-dimensional representations of neuronal morphology, and realistic biophysical modeling that can directly relate structural changes to altered neuronal firing patterns. To date however, tools capable of resolving, digitizing and analyzing neuronal morphology on both local and global scales, and with sufficient throughput and automation, have been lacking. The precision of existing image analysis-based morphometric tools is restricted at the finest scales, where resolution of fine dendritic features and spine geometry is limited by the skeletonization methods used, and by quantization errors arising from insufficient imaging resolution. We are developing techniques for imaging, reconstruction and analysis of neuronal morphology that capture both local and global structural variation. To minimize quantization error and evaluate more precisely the fine geometry of dendrites and spines, we introduce a new shape analysis technique, the Rayburst sampling algorithm that uses the original grayscale data rather than the segmented images for precise, continuous radius estimation, and multidirectional radius sampling to represent non-circular branch cross-sections and anisotropic structures such as dendritic spine heads, with greater accuracy. We apply the Rayburst technique to 3D neuronal shape analysis at different scales. We reconstruct and digitize entire neurons from stacks of laser-scanning microscopy images, as well as globally complex structures such as multineuron networks and microvascular networks. We also introduce imaging techniques necessary to recover detailed information on three-dimensional mass distribution and surface roughness of amyloid beta plaques from human Alzheimer's disease patients and from the Tg2576 mouse that expresses the "Swedish" mutation of the amyloid precursor protein. By providing true three-dimensional morphometry of complex histologic structures on multiple scales, the tools described in this report will enable multiscale biophysical modeling studies capable of testing potential mechanisms by which altered dendritic structure, spine geometry and network branching patterns that occur in normal aging and in many brain disorders, determine deficits of functions such as working memory and cognition.

Impact of diversity of antibiotic use on the development of antimicrobial resistance

OBJECTIVES

To evaluate the impact of different antibiotic strategies on acquisition of resistant microorganisms.

METHODS

A prospective study was conducted over a 44 month period in a single ICU. Four empirical antibiotic strategies for ventilator-associated pneumonia (VAP) were sequentially implemented. Over the initial 10 months, patient-specific antibiotic therapy was prescribed; then, 4 month periods of prioritization or restriction rotation cycles of various antimicrobial agents were implemented for a total of 24 months; and, finally, during the last 10 months (mixing period) the first-line antibiotic for VAP was changed following a pre-established schedule to ensure maximum heterogeneity. Antibiotic consumption was closely monitored every month, and antimicrobial resistance patterns were regularly assessed. Antimicrobial heterogeneity was estimated using a modified Peterson index (AHI) measuring the ratios for the five most used antibiotics. Colonization by targeted microorganisms and susceptibility patterns were compared with the patient-specific period.

RESULTS

Higher diversity of antibiotic prescription was obtained during patient-specific therapy (AHI = 0.93) or mixing periods (AHI = 0.95) than during prioritization (AHI = 0.70) or restriction periods (AHI = 0.68). High homogeneity was associated with increases in carbapenem-resistant Acinetobacter baumannii (CR-Ab) [relative risk (RR) 15.5; 95%CI 5.5-42.8], extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae (RR 4.2; 95%CI 1.9-9.3) and Enterococcus faecalis (RR 1.7; 95%CI 1.1-2.9). During the restriction period, incidence of ESBL-producing Enterobacteriaceae and E. faecalis returned to patient-specific rates but CR-Ab remained higher.

CONCLUSIONS

Antibiotic prescription patterns balancing the use of different antimicrobials should be promoted to reduce the selection pressure that aids the development of resistance.