Microwave surface impedance measurements on reduced graphene oxide

Here we report a non-contact method for microwave surface impedance measurements of reduced graphene oxide samples using a high Q dielectric resonator perturbation technique, with the aim of studying the water content of graphene oxide flakes. Measurements are made before, during and after heating and cooling cycles. We have modelled plane wave propagation of microwaves perpendicular to the surface of graphene on quartz substrates, capacitively coupled to a dielectric resonator. Analytical solutions are derived for both changes in resonant frequency and microwave loss for a range of water layer thicknesses. In this way we have measured the presence of adsorbed water layers in reduced graphene oxide films. The water can be removed by low temperature annealing on both single and multilayer samples. The results indicate that water is intercalated between the layers in a multilayer sample, rather than only being adsorbed on the outer surfaces, and it can be released by applying a mild heating.

Septicaemia due to enteric organisms is a later event in surgical infants requiring parenteral nutrition

INTRODUCTION

The purpose of this study was to determine whether, in surgical infants requiring parenteral nutrition (PN), septicaemia due to enterococci or Gram-negative bacilli occurs later than septicaemia due to coagulase-negative staphylococci (CNS).

PATIENTS/MATERIAL AND METHODS

We retrospectively studied 112 consecutive surgical infants (corrected gestational age up to 3 months) receiving PN for at least 5 days for congenital or acquired intestinal anomalies over a 2-year period (July 2007-June 2009). Data collected included diagnosis, duration of PN, episodes of septicaemia (defined as growth of bacteria from blood culture), and organisms cultured. We compared the time to first occurrence of septicaemia due to CNS with the times to first occurrence of septicaemia due to enterococci, Gram-negative bacilli, or other micro-organisms, using Kruskal-Wallis nonparametric ANOVA test and Dunn's multiple comparisons test. Data are given as median (range).

RESULTS

31 patients (28%) had a total of 65 episodes of septicaemia. Septicaemia due to CNS was most common, occurring in 22% of patients, after 17 days (1-239) of PN. Septicaemia due to enteric organisms was less common and occurred significantly later, at 59 (24-103) days for enterococci (p<0.01), and at 55 (30-106) days for Gram-negative bacilli (p<0.05).

CONCLUSIONS

Septicaemia due to enterococci or Gram-negative bacilli occurs later in the course of PN than septicaemia due to CNS, in surgical infants. This suggests that these infants become more vulnerable to the translocation of enteric micro-organisms after a longer period of parenteral nutrition.

Raman spectroscopy: a real-time tool for identifying microcalcifications during stereotactic breast core needle biopsies

Microcalcifications are an early mammographic sign of breast cancer and a target for stereotactic breast needle biopsy. We present here a Raman spectroscopic tool for detecting microcalcifications in breast tissue based on their chemical composition. We collected ex vivo Raman spectra from 159 tissue sites in fresh stereotactic breast needle biopsies from 33 patients, including 54 normal sites, 75 lesions with microcalcifications and 30 lesions without microcalcifications. Application of our Raman technique resulted in a positive predictive value of 97% for detecting microcalcifications. This study shows that Raman spectroscopy has the potential to detect microcalcifications during stereotactic breast core biopsies and provide real-time feedback to radiologists, thus reducing non-diagnostic and false negative biopsies.

Lattice resonances in antenna arrays for liquid sensing in the terahertz regime

Terahertz antenna arrays supporting narrow lattice resonances are proposed as an alternative sensor-on-chip approach to liquid sensing. An array of metallic rectangular antennas fabricated on a polyethylene naphthalate (PEN) substrate is used to demonstrate the sensing of a number of fluids. Good agreement is shown between experiment and simulation with Q-factors of around 20 and a figure-of-merit (FOM) of 3.80 being achieved. Liquid sensing with antenna arrays is simple both in terms of fabrication and setup. The working frequency can be tuned with a suitable choice of substrates and array parameters. The nature of the lattice resonance means that the whole sample is used to provide the conditions required for resonance occurrence, eliminating the need to preferentially locate the sample in small areas of high field concentration. The antenna arrays could also potentially be coupled with a microfluidic system for in situ sensing or used in a reflection setup.

[Atrial pacing for prevention of atrial fibrillation. Influence of septal atrial pacing, atrial overdrive and AV-delay-optimization on atrial fibrillation burden]

BACKGROUND

Atrial overdrive and optimized interatrial conduction time can reduce atrial fibrillation (AF). Increased ventricular stimulation results in a higher incidence of atrial fibrillation.

PATIENTS AND METHODS

In 25 patients with paroxysmal AF, a dual-chamber pacemaker (Identity DR 5370, St. Jude Medical) was implanted. Atrial leads were placed randomly either septal (n=12) or conventional (n=13). Dynamic atrial overdrive (DAO) was activated and the AV delay was optimized according to Koglek's method. After 3, 6, 9, and 12 months automatic mode switch (AF burden) was analysed.

RESULTS

No difference in implantation parameters were observed between groups. Technical implantation parameters were in the normal range for both groups. After 12 months patients in the septal group had less AF burden (1% vs. 7%, p=0.06), and the total number of AF episodes was reduced.

CONCLUSION

Septal pacing is safe. In combination with DAO and AV delay optimization it may reduce the AF burden, which can be observed after 12 months.

[Acute generalized exanthematous pustulosis associated with recurrent urinary tract infections]

Acute generalized exanthematous pustulosis (AGEP) is characterized by sudden onset of non-follicular aseptic pustules with erythema often accompanied by fever and leukocytosis. While the most frequent cause of AGEP is drug reactions, especially antibiotics. Occasional cases have been described as parainfectious. An 82-year-old female presented with recurrent AGEP along with a chronic urinary infection with Escherichia coli. Her cutaneous findings resolved following antibiotic therapy and prophylaxis. To the bets of our knowledge, this is the first case of AGEP associated with an Escherichia coli urinary tract infection.

Contribution of inflammation to the pathology of idiopathic pulmonary arterial hypertension in children

Idiopathic pulmonary arterial hypertension (IPAH) is an incurable disease of multifactorial origin. Inflammation is frequently observed in IPAH, but its role in the pathobiology is unclear. In this study the distribution, nature and number of inflammatory cells in periarterial infiltrates in lungs of children with IPAH, pulmonary arterial hypertension associated with congenital heart disease (APAH) and in normal lung tissue were characterised and compared using immunohistochemistry The influence of treatment with combined prostacyclin and endothelin receptor blockers was also studied. In children with IPAH, both treated and untreated, but not in children with APAH or normal children, extensive periarterial infiltrates were present comprising macrophages and T lymphocytes with S100A4- and bone morphogenetic protein receptor type-2 (BMPR2)-positive cells. Although rarely co-expressing macrophage-specific antigens, BMPR2-positive cells were frequently closely associated with macrophages and lymphocytes. They were more abundant around peripheral arteries of children with IPAH than in APAH or normal lungs (15.1 (3.5), 2.3 (0.9) and 2.3 (0.9) cells/mm external elastic lamina, respectively; p<0.01 for IPAH vs APAH or normal lungs). Prostacyclin with endothelin receptor blockade resulted in a significant reduction in endothelial cell activation as indicated by human leucocyte antigen (HLA)-DR expression (treated 17% vs untreated 100%, p<0.002). This study shows that pulmonary inflammation is present in the lungs of children with IPAH. This may indicate a role for inflammation in the pathobiology of IPAH and provide the rationale for novel therapeutic intervention.

Quantitative detection of circulating endothelial cells in vasculitis: comparison of flow cytometry and immunomagnetic bead extraction

BACKGROUND

Circulating endothelial cells (CECs) are biomarkers for endothelial cell (EC) injury and are quantified using immunomagnetic bead extraction (IBE), or flow cytometry (FC). Reports suggest that there is good agreement between these methods for CEC quantification.

OBJECTIVES

We examined levels of agreement between these techniques in children with systemic vasculitis.

METHODS

We added HUVEC or human pulmonary artery EC to whole blood to optimize FC gating strategies for EC. EC-optimized FC was then compared with IBE for CEC enumeration in 25 children with vasculitis and 20 healthy controls.

RESULTS

Using Bland-Altman analysis, agreement between IBE and EC-optimized FC was poor in children with vasculitis (n = 25) and healthy controls (n = 20): IBE consistently detected higher values than the EC-optimized FC method: the mean difference between the two techniques was 60 CECs mL(-1), 95% CI +/-374 CECs mL(-1) (paired analyses of 45 individuals). Agreement was poorest for vasculitis patients: mean difference (IBE - EC-optimized FC) 120 CECs mL(-1), 95% CI +/-460 CECs mL(-1) (P = 0.018). We identified three reasons for this discrepancy: (i) sub-optimal FC gating parameters previously used for detecting CECs; (ii) inherent lack of sensitivity of FC compared with IBE for CEC rare event detection; and (iii) use of lysis buffers required for FC causing CEC lysis.

CONCLUSIONS

There was poor agreement between EC-optimized FC and IBE for the quantification of CECs from children with active vasculitis and controls. We emphasize that in this clinical setting the two techniques are not directly comparable when comparing results obtained using these different methodologies.

Visual outcome and corneal changes in children with chronic blepharokeratoconjunctivitis

OBJECTIVE

To describe the cause, management, and effect of chronic blepharokeratoconjunctivitis (BKC) on the cornea and visual function in children.

DESIGN

Noncomparative, interventional, retrospective case series.

PARTICIPANTS

Twenty-seven children with BKC.

METHODS

Presenting age, best-corrected visual acuity (BCVA), refractive error, and any corneal or eyelid pathologic features were recorded. Treatment included modified lid hygiene, topical antibiotics, and steroids. Systemic therapy included oral antibiotics and, from 2003 onward, flaxseed oil as an alternative to long-term antibiotics. Amblyopia therapy included refractive correction, occlusion, or atropine therapy.

MAIN OUTCOME MEASURES

Corneal and eyelid status, visual acuity (VA), and refractive error at final examination.

RESULTS

Mean age at presentation was 6.9 years (range, 7 months-15.9 years), and mean follow-up was 2.3 years (range, 5 months-6.1 years). All patients had discomfort, conjunctival injection, and signs of posterior blepharitis at presentation. Photophobia was reported in 14 patients (52%), whereas anterior eyelid inflammation was noted in 6 (22%). Acne rosacea was confirmed in 3 patients (11%). Corneal involvement occurred in 44 eyes (81%), and a history of recurrent chalazia was seen in 18 patients (67%). Median monocular BCVAs in affected eyes were 0.28 logarithm of the minimum angle of resolution (logMAR) units (interquartile range [IqR], 0.02-0.40) at presentation and 0.02 logMAR units (IqR, 0.00-0.18) at last visit. Best-corrected VA improved in 70% of affected eyes and remained unchanged in 30%. Superimposed amblyopia was present and treated in 15 patients (48%). All 8 patients (20%) who failed to achieve VA of 0.2 logMAR units or better at the final examination had bilateral corneal involvement at presentation. One child experienced a systemic side effect from oral antibiotics. No child had significant side effects from topical treatment. Twelve patients (44%) received flaxseed oil as part of their tapering regimen. A 2-year lag between symptom onset and treatment resulted, on average, in a reduction of 0.06 logMAR units of VA (95% confidence interval, 0.00-0.12; P = 0.054).

CONCLUSIONS

These findings suggest that visual loss may be significant in BKC and that delayed treatment may result in decreased final BCVA. Adequate management needs both topical and systemic treatment. Flaxseed oil may be an effective antiinflammatory nutritional therapy alternative to long-term antibiotics.

T cell activation profiles in Kawasaki syndrome

Superantigens (SAgs) are potent stimulators of T cells bearing specific Vbeta T cell receptors (TCR) and may play a role in the pathogenesis of Kawasaki syndrome (KS), although despite 15 years of intense study this area remains controversial. Because SAgs can cause Vbeta restricted T cell activation in the absence of Vbeta skewing the aims of this study were to describe a flow cytometric protocol to study both CD4 and CD8 Vbeta repertoires, and CD69 expression across the CD4 and CD8 Vbeta repertoire in children with KS. Sixteen children with KS were studied. There was no significant increase in overall peripheral blood CD4 or CD8 T cell activation as determined by CD69 expression. However, Vbeta restricted CD4 and/or CD8 activation was observed in eight of 11 (72%) of the KS patients, a finding not observed in healthy controls. Thirteen of 16 (81%) of the KS patients had evidence of either Vbeta skewing (particularly CD4 Vbeta2 and Vbeta5.1) and/or Vbeta restricted activation. Three patients had Vbeta restricted activation in the absence of skewing. We suggest that these preliminary observations highlight the many layers of complexity when considering T cell activation in KS, which could explain some of the conflicting studies regarding peripheral blood T cell activation and Vbeta skewing. It is likely that in order to move forward with this debate a combination of detailed microbiological, immunological and molecular techniques applied to individual patients will be required ultimately to prove or refute the SAg hypothesis of KS.

Natural human antibodies to pneumococcus have distinctive molecular characteristics and protect against pneumococcal disease

The molecular and functional characteristics of natural antibody from the preimmune repertoire have not been explored in detail in man. We describe seven human IgM monoclonal antibodies selected on the basis of pneumococcal polysaccharide binding that share both molecular and functional characteristics with natural antibody, suggesting a common B cell lineage origin. Unlike class-switched antibodies, which are serotype-specific, the antibodies were polyreactive and bound all pneumococcal polysaccharide capsular serotypes tested. Some bound endogenous antigens, including blood group antigens and intermediate filament proteins. All the antibodies used unmutated heavy chain V (IGHV) that are expressed at an increased frequency in the elderly and in the preimmune repertoire. The CDR3 was characterized by long length (mean aa 18.4 (+/-4.2) and selective use of IGHD6 (P < 0.001) and IGHJ6 (P < 0.01) family genes. The clones expressing IGHV1-69 and IGHV 3-21 provided significant passive protection against invasive pneumococcal disease in vivo.