Finite magnetic relaxation in x-space magnetic particle imaging: Comparison of measurements and ferrohydrodynamic models.

Magnetic Particle Imaging (MPI) is an emerging tomographic imaging technology that detects magnetic nanoparticle tracers by exploiting their non-linear magnetization properties. In order to predict the behavior of nanoparticles in an imager, it is possible to use a non-imaging MPI relaxometer or spectrometer to characterize the behavior of nanoparticles in a controlled setting. In this paper we explore the use of ferrohydrodynamic magnetization equations for predicting the response of particles in an MPI relaxometer. These include a magnetization equation developed by Shliomis (Sh) which has a constant relaxation time and a magnetization equation which uses a field-dependent relaxation time developed by Martsenyuk, Raikher and Shliomis (MRSh). We compare the predictions from these models with measurements and with the predictions based on the Langevin function that assumes instantaneous magnetization response of the nanoparticles. The results show good qualitative and quantitative agreement between the ferrohydrodynamic models and the measurements without the use of fitting parameters and provide further evidence of the potential of ferrohydrodynamic modeling in MPI.

Molecular epidemiology of Staphyloccocus aureus colonization in the Old Order of Amish of Lancaster County, Pennsylvania, USA.

Transmission of Staphylococcus aureus colonization in community-based populations is not well understood. We sought to describe the molecular epidemiology of S. aureus colonization in the Old Order Amish. The study was a prospective, observational study of healthy adults and their same-sex siblings who were cultured from the anterior nares twice. S. aureus isolates were characterized using spa typing. Overall, 40% (159/398) of the study population was colonized with S. aureus. There were 84 spa types with the most abundant spa types being t012 (13%) and t021 (7%). There was no clustering of spa types within sibling groups; however, there was clustering within households. There were 111 S. aureus-colonized participant pairs living within the same household. Of these, 47% had concordant spa types. The diversity of spa types across a relatively isolated, genetically homogenous population with a similar lifestyle is striking. Taken together this suggests that S. aureus transmission is a local phenomenon limited to very close contact.

Tuberculosis peer educators: personal experiences of working with socially excluded communities in London.

SETTING: Peer education is a relatively unexplored intervention for tuberculosis (TB) control, particularly among socially excluded communities. In London, peer educators are used to raise awareness of TB and promote uptake of radiological screening among people using homeless and/or drug and alcohol treatment services. OBJECTIVE: To understand the motivation and personal impact of being a peer educator on people with experience of anti-tuberculosis treatment, homelessness and addiction. DESIGN: In-depth semi-structured interviews with peer educators were recorded and transcribed, and then analysed using a grounded theory approach to identify themes. Reflexivity and thick description were used to support transparency of findings. RESULTS: Becoming a peer educator supports individuals in making sense of past experiences and renewing their sense of self. The role places value on personal experience and the communication approach this supports. The project environment is an important motivator, providing the peer with structure, social support and respect. CONCLUSION: Being a peer educator with experience of homelessness and addiction can be beneficial and empowering and help long-term recovery. Peers are an underused resource for strengthening TB control among socially excluded populations. There is a need for further research into the contribution of peers to TB control, including analyses of economic effectiveness.

To speak, or not to speak? The feasibility of imaging overt speech in children with epilepsy.

We systematically compared fMRI results for covert (silent) and overt (spoken) versions of a language task in a representative sample of children with lesional focal epilepsy being considered for neurosurgical treatment (N=38, aged 6-17 years). The overt task was advantageous for presurgical fMRI assessments of language; it produced higher quality scans, was more sensitive for identifying activation in core language regions on an individual basis, and provided an online measure of performance crucial for improving the yield of presurgical fMRI.

The effects of experience on the energy cost of wheelchair propulsion.

BACKGROUND: Gross mechanical efficiency (GE) of experienced wheelchair users is significantly higher than novice able-bodied individuals suggesting energy expenditure (EE) may be reduced in experienced individuals. With knowledge of the energy expended during wheelchair propulsion, nutritional recommendations can be provided for individuals in their early stages of rehabilitation and for habituated wheelchair users. AIM: To investigate the effects of experience on EE during wheelchair propulsion at fixed power outputs (PO's). DESIGN: This was an experimental study. SETTING: The experiment was conducted in a controlled University laboratory. POPULATION: Thirty-one individuals took part in this study. METHODS: Participants were assigned to a group in accordance to their wheelchair propulsion experience: 1) novice able-bodied individuals (NOV; N.=11), 2) able-bodied individuals habituated to three weeks practice (PRAC; N.=11) and 3) experienced paraplegic daily-wheelchair users (EXP; N.=9). Oxygen uptake, EE, GE% and HR were measured during wheelchair propulsion on a motorised treadmill at 10, 18 and 26 W. RESULTS: Energy expenditure analysis revealed a significant main effect of PO and group (P<0.01) and a significant group by PO interaction (P<0.01). Follow-up pair-wise comparisons revealed significantly lower EE in EXP compared to both other groups (P<0.01), but no difference was shown between NOV and PRAC (P=0.15). A lower relative EE of 20, 22 and 32% was reported in the EXP group compared to the NOV group at 10, 18 and 26 W respectively. In comparison to the PRAC group, the EE of the EXP group was 10, 16 and 26% lower in relative terms at the same PO's respectively. CONCLUSION: The EXP expended less EE compared to both NOV and PRAC. CLINICAL REHABILITATION IMPACT: This finding has great implications for nutritionists and health care professionals working in the field of physical activity and weight management since the EE is influenced by experience.

Evidence that oxytocin is a physiological component of LH regulation in non-pregnant women.

BACKGROUND: Regulation of the LH surge is central to the functioning of the female ovulatory cycle. In animal models, oxytocin has been shown to alter LH activity. Oxytocin advanced the LH surge and, conversely, oxytocin receptor antagonists inhibited full production of the LH surge in rats. Few data exist on the possibility that oxytocin modulates LH in women. METHODS: Ten non-pregnant women participated in this study over two menstrual cycles. One cycle was a control cycle, and the other a trial cycle; the two were separated by at least one cycle. When the diameter of an ovarian follicle was >15 mm, a subject was allocated at random into either a control or treatment group. In a control cycle, volunteers received normal saline; in a treatment cycle, volunteers received an oxytocin antagonist (atosiban). RESULTS: For treatment cycles, the maximum LH concentration was significantly less than that in control cycles (42.1 +/- 6.2 versus 60.3 +/- 8.3 IU/l respectively; P < 0.05). Maximum FSH and estradiol concentrations were not significantly different between the two groups. CONCLUSIONS: The results indicated that inhibition of endogenous oxytocin affects the endocrinology of the ovulatory cycle in women, and strongly suggest that oxytocin has a role in the physiological processes of LH regulation.

Comparison of four echocardiographic techniques for measuring left ventricular ejection fraction.

Accurate quantitative measurement of left ventricular (LV) ejection fraction (EF) by 2-dimensional echocardiography is limited by subjective visual endocardial border detection. Both harmonic and precision contrast microbubbles provide better delineation of endocardial borders than fundamental imaging. The aim of this study was to correlate 2-dimensional echocardiographic quantification of LVEF measured by 4 currently available techniques with radionuclide angiography. A total of 50 patients who underwent radionuclide (EF) measurement (47 of 50 had technically difficult echocardiograms by fundamental imaging) underwent echocardiography by 4 methods: fundamental alone, fundamental with contrast, harmonic alone, and harmonic with contrast. Three echocardiologists measured the biplane 2-dimensional echocardiographic LVEF independently and were blinded to radionuclide angiography. The correlation of echocardiographic EF with radionuclide EF improved incrementally with each method. However, contrast with harmonic imaging provided the closest correlation (r = 0.95, 0.96, and 0.95 as assessed by the 3 independent analysts.

A minimal tiling path cosmid library for functional analysis of the Pseudomonas aeruginosa PAO1 genome.

Pseudomonas aeruginosa is an important pathogenic and environmental bacterium, with the most widely studied strain being PAO1. Using the PAO1 reference cosmid library and the recently completed PAO1 genome sequence, we have mapped a minimal tiling path across the genome using a two-step strategy. First, we sequenced both ends of a set of over 500 random and previously mapped clones to create a backbone. Second, we end-sequenced a second set of cosmid clones that were identified to lie within the larger gaps using hybridization of the reference library filters with probes designed against sequences at the center of each gap. The minimal tiling path was calculated using the program Domino (http://www.bit.uq.edu.au/download/), with the overlap between adjacent clones set to 5 kb (where possible) to minimize the chance of truncating genes. This yielded a minimal tiling cosmid library (334 clones) covering 93.7% of the genome in 57 contigs. This library has reduced to a workable set the number of clones required to represent the majority of the P. aeruginosa genome and gives the precise location of each cosmid, enabling most genes of interest to be located on clones without further screening. This library should prove a useful resource to accelerate functional analysis of the P. aeruginosa genome.

Predictive value of left ventricular ejection fraction in stem cell transplantation.

We evaluated predictive value of left ventricular ejection fraction at rest (REF) and its increment with exercise (deltaEF) on autologous and allogeneic stem cell transplantation mortality. In a 7 year period, a total of 163 patients evaluated for stem cell transplantation were studied. All were followed for at least 3 months after the transplant. REF was discriminatory for peritransplant mortality only in younger (<43 years) patients (n = 66), particularly those who underwent autologous transplantation (n = 30). Resting ejection fraction was not a discriminator for early death in any other subgroup. Cardiac reserve (deltaEF) was significantly lower in patients (n = 35), who died early. The finding was most prominent in younger patients who underwent autologous transplantation (n = 26). Combination of decreased REF and low deltaEF (n = 18) was associated with high peritransplant mortality (56%), after both autologous and allogeneic transplantation. A low REF with an appropriate deltaEF (n = 43) was associated with a 19% peritransplant mortality and no deaths in the autologous group. These observations indicate that resting ejection fraction is of only limited value for pretransplant evaluation. However, measurement of cardiac reserve during exercise can provide important prognostic information before stem cell transplantation.

Apolipoprotein E allele epsilon 4, dementia, and cognitive decline in a population sample.

From clinically based series it has been proposed that, in homozygotes for the apolipoprotein E epsilon 4 (apoE epsilon 4) allele, Alzheimer's disease is almost inevitable by the age of 80. A population sample of persons aged 70 years and over was interviewed in 1990-91 to ascertain the presence of dementia or cognitive impairment. The sample was reinterviewed in 1994, when the apoE genotype was also determined. Prevalence data for the 638 persons who completed the second examination revealed a linear association between having an apoE epsilon 4 allele and both dementia and cognitive impairment (for heterozygotes, odds ratio for dementia 1.89, 95% confidence interval 1.04-3.44 and for homozygotes OR 3.58, 95% CI 1.08-11.82; both adjusted for age). However, even in subjects homozygous for epsilon 4 the estimated prevalence of dementia by age 90 was only about 50%. Persons with one or two epsilon 4 alleles were more likely to have a family history of dementia than those with none. This study confirms in a population sample that the epsilon 4 allele is a risk factor for dementia, but refutes the suggestion that homozygosity for the epsilon 4 allele is sufficient for the development of Alzheimer's disease: persons with either one or two epsilon 4 alleles may reach late old age without cognitive impairment.

Subband image coding using watershed and watercourse lines of the wavelet transform.

Reports progress in primitive-based image coding using nonorthogonal dyadic wavelets. A 3D isotropic wavelet is used to approximate the difference-of-Gaussians (D-o-G) operator. Convolution of the image with dilated versions of the wavelet produces three band-pass signals that approximate multiscale smoothed second derivatives. An additional convolution of the image with a Gaussian-shaped low-pass wavelet creates a fourth subband signal that preserves low-frequency information not described by the three band-pass signals. The authors show that the original image can be recovered from the watershed and watercourse lines of the three band-pass signals plus the lowpass subband signal. By thresholding the watershed/watercourse representation, subsampling the low-pass subband, and using edge post emphasis, the authors achieve data reduction with little loss of fidelity. Further compression of the watersheds and watercourses is achieved by chain coding their shapes and predictive coding their amplitudes prior to lossless arithmetic coding. Results are presented for grey-level test images at data rates between 0.1 and 0.3 b/pixel.