An exact surface-integral approach for accurate interferometric microscopy of single nanoparticles.

We present a half-plane surface-integral equation (SIE) approach for modeling the optical phase response of a single nanowire under phase-stepping interferometric (PSI) microscopy. This approach calculates scattered fields exactly from the Helmholtz equation in this 2D problem, obviating the need for ray-optic approximations. It is demonstrated that refractive index metrology is enabled by this method, with precision as low as 7 × 10(-5) possible for current state-of-the-art PSI microscopes. For nanowires of known refractive index, radii as small as 0.001λ are shown to yield a measurable phase signal and are therefore potentially measurable by this approach. Measurements are also demonstrated to be relatively insensitive to the spectral and coherence characteristics of the light source, the illumination conditions, and variations in nanowire cross-section shape. Prospects for measuring both the radius and refractive index simultaneously, and scope for generalizing this approach to arbitrary nanoparticle shapes are discussed.

Measuring nanoparticle size using phase-stepping interferometry: quantifying measurement sensitivity to surface roughness.

A method for sizing nanoparticles using phase-stepping interferometry has been developed recently by Little et al. [Appl. Phys. Lett. 103, 161107 (2013)]. We present an analytical procedure to quantify how sensitive measurement precision is to surface roughness. This procedure computes the standard deviation in the measured phase as a function of the surface roughness power spectrum. It is applied to nanospheres and nanowires on a flat plane and also a flat plane in isolation. Calculated sensitivity levels demonstrate that surface roughness is unlikely to be the limiting factor on measurement precision when measuring nanoparticle size using this phase-shifting-interferometry-based technique. The need to use an underlying surface that is very smooth when measuring nanoparticles is highlighted by the analysis.

Antigen sequence typing of outer membrane protein (fetA) gene of Neisseria meningitidis serogroup A from Delhi & adjoining areas.

BACKGROUND & OBJECTIVES: Meningitis caused by Neisseria meningitidis is a fatal disease. Meningococcal meningitis is an endemic disease in Delhi and irregular pattern of outbreaks has been reported in India. All these outbreaks were associated with serogroup A. Detailed molecular characterization of N. meningitidis is required for the management of this fatal disease. In this study, we characterized antigenic diversity of surface exposed outer membrane protein (OMP) FetA antigen of N. meningitidis serogroup A isolates obtained from cases of invasive meningococcal meningitis in Delhi, India. METHODS: Eight isolates of N. meningitidis were collected from cerebrospinal fluid during October 2008 to May 2011 from occasional cases of meningococcal meningitis. Seven isolates were from outbreaks of meningococcal meningitis in 2005-2006 in Delhi and its adjoining areas. These were subjected to molecular typing of fetA gene, an outer membrane protein gene. RESULTS: All 15 N. meningitides isolates studied were serogroup A. This surface exposed porin is putatively under immune pressure. Hence as a part of molecular characterization, genotyping was carried out to find out the diversity in outer membrane protein (FetA) gene among the circulating isolates of N. meningitidis. All 15 isolates proved to be of the same existing allele type of FetA variable region (VR) when matched with global database. The allele found was F3-1 for all the isolates. INTERPRETATION & CONCLUSIONS: There was no diversity reported in the outer membrane protein FetA in the present study and hence this protein appeared to be a stable molecule. More studies on molecular characterization of FetA antigen are required from different serogroups circulating in different parts of the world.

Measuring nanoparticle size using optical surface profilers.

Optical surface profilers are state-of-the-art instruments for measuring surface height profiles. They are not conventionally applied to nanoparticle measurements due to the presence of diffraction artifacts. Here we use a theoretical model based on wave-optics to account for diffraction-based artifacts in optical surface profilers. This then enables accurate measurement of nanoparticles size of a known geometry. The model is developed for both phase shifting interferometry and vertical scanning interferometry modes of operation. It is demonstrated that nanosphere radii as small as 12 nm, and nano-cylinder radii as small as 10-15 nm can be measured from a standard profile measurement using phase shifted interferometry interpreted using the wave-optics approach.

Evaluation of a coping kit for children with challenging behaviors in a pediatric hospital.

This study attempted to answer the question, "Do nurses perceive coping kits to be effective at meeting the needs of hospitalized children with developmental disabilities who are at increased risk for challenging behaviors?" A cross-sectional post-test survey study design was used, with a convenience sample of 24 registered nurses at a Midwestern free-standing children's hospital. A coping kit with simple communication cards, social script book, and distraction items (toys) was developed to enhance communication and distract children with developmental disabilities (including autism spectrum disorder) undergoing procedures in the hospital. A modified version of Hudson's (2006) intervention effectiveness survey was used to measure the nurse's perception of the effectiveness of the coping kit. Nurses perceived the coping kits to be effective for decreasing their patient's anxiety, calming the child's behavior, and increasing cooperation during procedures. The nurse can develop a plan of care that includes a coping kit to help gain cooperation with the hospitalized child with challenging behaviors.

Transcranial direct current stimulation of the premotor cortex aimed to improve hand motor function in chronic stroke patients.

OBJECTIVE: To investigate the effects of single-session premotor and primary motor tDCS in chronic stroke patients with relation to possible inter-hemispheric interactions. METHODS: Anodal tDCS of either M1 or premotor cortex of the side contralateral to the paretic hand, cathodal tDCS of the premotor cortex of the side ipsilateral to the paretic hand and sham stimulation were performed in 12 chronic stroke patients with mild hand paresis in a balanced cross-over design. The Jebsen-Taylor Hand Function test, evaluating the time required for performance of everyday motor tasks, was employed. RESULTS: The repeated-measure ANOVA with Greenhouse-Geisser correction showed significant influence of the stimulation type (factor SESSION; F(2.6, 28.4) = 47.3, p < 0.001), the test performance time relative to stimulation (during or after tDCS; factor TIME, F(1.0, 11.0) = 234.5, p < 0.001) with higher effect after the stimulation and the interaction SESSION*TIME (F(1.7, 1.2) = 30.5, p < 0.001). All active conditions were effective for the modulation of JTT performance, though the highest effect was observed after anodal tDCS of M1, followed by effects after anodal stimulation of the premotor cortex contralateral to the paretic hand. Based on the correlation patterns, the inhibitory input to M1 from premotor cortex of another hemisphere and an excitatory input from the ipsilesional premotor cortex were suggested. CONCLUSION: The premotor cortex is a promising candidate area for transcranial non-invasive stimulation of chronic stroke patients.

Evaluation of nucleic acid probe for rapid identification of Mycobacterium tuberculosis complex in extra-pulmonary culture isolates.

Patients infected with Non-tuberculous mycobacteria (NTM) usually do not respond to conventional anti-tubercular treatment and are misdiagnosed as infection with multi-drug resistant strains of mycobacterium tuberculosis (M.tb) due to lack of correct species identification, particularly in the developing countries like India. One of the challenges faced by clinicians in the treatment of tuberculosis is the absence of an easy, reliable and rapid identification tool that can accurately differentiate disease caused by M.tb complex from NTM. Keeping this in consideration, the performance of species specific nucleic acid probe i.e. Accuprobe was assessed and compared with conventional niacin production, nitrate reductase assay techniques for identification of M.tb complex in 80 mycobacterial isolates obtained from different extra-pulmonary sites. Accuprobe identified 62 isolates (77.5%) as M. tuberculosis complex and remaining 18 isolates (22.5%) as NTM whereas 64 isolates (80%) were identified as M.tb and rest 16 (20%) were interpreted as NTM by conventional biochemical techniques. The overall agreement between both techniques was 96.9% The sensitivity, specificity, positive predictive value(PPV) and negative predictive value (NPV) shown by accuprobe were 96.9%, 100%, 96.9%, and 88.9% respectively. Thus, accuprobe has showed impressive sensitivity and specificity giving results in < 3 hrs from culture-positive isolates and have sure edge over conventional biochemical methods which are, nonetheless, labour intensive and cumbersome to perform thus delaying prompt mycobacterial identification.

Measured vs Predicted Energy Expenditure in Mechanically Ventilated Adults With Acute, Traumatic Spinal Cord Injuries.

BACKGROUND: Research regarding the impact of acute spinal cord injury (aSCI) on energy expenditure is limited. Patients with aSCI are prone to complications of both over- and under-feeding, making appropriate nutrition support pivotal to patient care. The purpose of this study was to describe energy expenditure and assess the performance of predictive equations in mechanically ventilated adults with aSCI. METHODS: Adult patients admitted to a single trauma center from March 2017 through June 2018 with aSCI and a documented indirect calorimetry (IC) within 6 weeks of injury were included for analysis. Predictive equations evaluated included Penn State 2003b (PS 2003b), the derived Weir equation, 25 kcal/kg and 30 kcal/kg. Sub-set analysis was performed for patients with and without obesity, isolated aSCI, and concomitant traumatic injuries. RESULTS: On hundres fifteen IC studies in 51 patients were included for analysis. Median energy expenditure was 1747 kcal/day (interquartile range [IQR], 1492-2099 kcal/day), or 22.7 kcal/kg (IQR, 19.3-25.9 kcal/kg). When stratified by hospital day, energy expenditure ranged from 20 to 25 kcal/kg. PS 2003b and the derived Weir equation had similar correlation coefficients (r = 0.81 and 0.82, respectively). The 25 and 30 kcal/kg performed unacceptably (r = 0.61). PS 2003b predicted within 10% of measured energy expenditure most frequently. All equations were biased towards overfeeding, except for PS 2003b in the obese subset. CONCLUSION: In the absence of IC, PS 2003b or the derived Weir equation may be acceptable predictive equations in this population. However, bedside clinicians should monitor carefully for signs and symptoms of overfeeding.

Bacteraemia with pleural effusions complicating typhoid fever caused by high-level ciprofloxacin-resistant Salmonella enterica serotype Typhi.

An unusual case of bacteraemia with bilateral pleural effusion caused by Salmonella enterica serotype Typhi in a 10-year-old previously healthy girl is reported. The organism was isolated from pleural fluid aspirate and from blood, and exhibited high-level ciprofloxacin resistance (MIC 16 µg/ml) associated with triple mutations in the QRDRs of the gyrA and parC genes leading to the amino-acid changes Ser83→Phe and Asp87→Asn in gyrA and Ser80→Ile in parC. The patient was successfully treated with parenteral ceftriaxone and intercostal chest tube drainage. The case is notable because of the important issue of antimicrobial resistance in S. Typhi and the therapeutic dilemma faced by clinicians regarding the empirical use of ciprofloxacin and newer fluoroquinolones.

Photoreflectance/scattering measurements of spider silks informed by standard optics.

The silks of certain orb weaving spiders are emerging as high-quality optical materials. This motivates study of the optical properties of such silk and particularly the comparative optical properties of the silks of different species. Any differences in optical properties may impart biological advantage for a spider species and make the silks interesting for biomimetic prospecting as optical materials. A prior study of the reflectance of spider silks from 18 species reported results for three species of modern orb weaving spiders (Nephila clavipes, Argiope argentata and Micrathena Schreibersi) as having reduced reflectance in the UV range. (Modern in the context used here means more recently derived.) The reduced UV reflectance was interpreted as an adaptive advantage in making the silks less visible to insects. Herein, a standard, experimental technique for measuring the reflectance spectrum of diffuse surfaces, using commercially available equipment, has been applied to samples of the silks of four modern species of orb weaving spiders: Phonognatha graeffei, Eriophora transmarina, Nephila plumipes and Argiope keyserlingi. This is a different technique than used in the previous study. Three of the four silks measured have a reduced signal in the UV. By taking the form of the silks as optical elements into account, it is shown that this is attributable to a combination of wavelength-dependent absorption and scattering by the silks rather than differences in reflectance for the different silks. Phonognatha graeffei dragline silk emerges as a very interesting spider silk with a flat 'reflectance'/scattering spectrum which may indicate it is a low UV absorbing dielectric micro-fibre. Overall the measurement emerges as having the potential to compare the large numbers of silks from different species to prospect for those which have desirable optical properties.

Concomitant TB and cryptococcosis in HIV-infected patients.

Four cases of concomitant tuberculosis and cryptococcosis infection in HIV-positive patients are described. As the HIV pandemic progresses and the proportion of patients with end-stage disease increases, a high suspicion of incidence and unusual forms of infections must always be kept in mind.

Use of rK39 for diagnosis of post kala-azar dermal leishmaniasis in Nepal.

A recently developed nitrocellulose-based dipstick test, rK39, has been widely used for the diagnosis of kala-azar. In this study, we evaluated its use for the diagnosis of post kala-azar dermal leishmaniasis (PKDL). We also investigated the time taken by patients to develop PKDL after apparent cure of kala-azar (visceral leishmaniasis, VL) and the time taken by patients to come to the hospital after the appearance of symptoms of PKDL. A majority of patients developed the disease within three years after the apparent cure of kala-azar (KA). A majority of patients sought treatment within five years after the onset of PKDL. The amastigotes of Leishmania donovani bodies (LDBs) were demonstrated in 70, 20, and 20% of slit-skin smears (SSS) prepared, respectively, from nodular, papular, and macular forms. The presence of highest density (6+) LDBs in the SSS of 20% of nodular PKDL patients indicated that they may have acted as reservoir in the community. Other reservoirs are not known in Nepal. Only 8% cases were detected by aldehyde test. Although this test is obsolete it is still used in rural parts of Nepal. The dipstick (rK39) was 96% sensitive and 100% specific to diagnose PKDL. Its positive predictive value, negative predictive value, and diagnostic efficacy were 100, 91, and 97% respectively. Due to the advantage of cost compared with the direct agglutination test (DAT), and being easy to use and store in field conditions, rK39 is a good tool to diagnose PKDL in rural situations. All the PKDL patients were cured of the disease after treatment by SAG.

Isospora belli infection in a malnourished child.

Isospora belli, a coccidian parasite usually causes a self limiting illness of acute onset with fever, diarrhoea and colicky pain in a normal host. In immunocompromised patients human isosporiasis becomes chronic. We report a case of a malnourished 9 year old female child who presented with complaints of loose stools, nausea, vomiting and weight loss for the past three months. Stool examination revealed immature oocysts of Isospora belli. The patient was successfully treated with TMP-SMX.

Resistance patterns of urinary isolates in a tertiary Indian hospital.

BACKGROUND: To analyze the pathogenic organisms recovered from patients with urinary tract infection in a tertiary Indian hospital setting along with determination of the occurrence and antimicrobial sensitivity of uropathogens on a retrospective basis during a period of one year. METHODS: A total of 5073 urine samples were processed. Urine culture was done using conventional microbiological techniques. Biochemical testing was used to identify the organisms and antibiotic sensitivity was done by the Kirby Bauer method. RESULTS: A total of 2436 uropathogens were isolated. E coli were seen in 50.7% samples followed by Klebsiella sp (27.6%). Staphylococcus aureus was the commonest Gram-positive isolate (1.5%). Urinary tract infection (UTI) was seen in 70.5% females as compared to 29.5% males. A high recovery of isolates was noted from July to September. Multi drug resistance was commonest with Enterococcus (78.8%) followed by Pseudomonas (65.1%). Drugs, which retained usefulness for Gram-negative isolates, were amikacin, norfloxacin and cefotaxime. For Gram-positive isolates, vancomycin, teicoplanin, lincomycin and Norfloxacin were very effective. CONCLUSIONS: Our study highlights the changing etiology of UTI and emergence of drug resistance within the Indian subcontinent.

Variance of permutation entropy and the influence of ordinal pattern selection.

Permutation entropy (PE) is a widely used measure for complexity, often used to distinguish between complex systems (or complex systems in different states). Here, the PE variance for a stationary time series is derived, and the influence of ordinal pattern selection, specifically whether the ordinal patterns are permitted to overlap or not, is examined. It was found that permitting ordinal patterns to overlap reduces the PE variance, improving the ability of this statistic to distinguish between complex system states for both numeric (fractional Gaussian noise) and experimental (semiconductor laser with optical feedback) systems. However, with overlapping ordinal patterns, the precision to which the PE variance can be estimated becomes diminished, which can manifest as increased incidences of false positive and false negative errors when applying PE to statistical inference problems.

Permutation entropy with vector embedding delays.

Permutation entropy (PE) is a statistic used widely for the detection of structure within a time series. Embedding delay times at which the PE is reduced are characteristic timescales for which such structure exists. Here, a generalized scheme is investigated where embedding delays are represented by vectors rather than scalars, permitting PE to be calculated over a (D-1)-dimensional space, where D is the embedding dimension. This scheme is applied to numerically generated noise, sine wave and logistic map series, and experimental data sets taken from a vertical-cavity surface emitting laser exhibiting temporally localized pulse structures within the round-trip time of the laser cavity. Results are visualized as PE maps as a function of embedding delay, with low PE values indicating combinations of embedding delays where correlation structure is present. It is demonstrated that vector embedding delays enable identification of structure that is ambiguous or masked, when the embedding delay is constrained to scalar form.

Insights on correlation dimension from dynamics mapping of three experimental nonlinear laser systems.

BACKGROUND: We have analysed large data sets consisting of tens of thousands of time series from three Type B laser systems: a semiconductor laser in a photonic integrated chip, a semiconductor laser subject to optical feedback from a long free-space-external-cavity, and a solid-state laser subject to optical injection from a master laser. The lasers can deliver either constant, periodic, pulsed, or chaotic outputs when parameters such as the injection current and the level of external perturbation are varied. The systems represent examples of experimental nonlinear systems more generally and cover a broad range of complexity including systematically varying complexity in some regions. METHODS: In this work we have introduced a new procedure for semi-automatically interrogating experimental laser system output power time series to calculate the correlation dimension (CD) using the commonly adopted Grassberger-Proccacia algorithm. The new CD procedure is called the 'minimum gradient detection algorithm'. A value of minimum gradient is returned for all time series in a data set. In some cases this can be identified as a CD, with uncertainty. FINDINGS: Applying the new 'minimum gradient detection algorithm' CD procedure, we obtained robust measurements of the correlation dimension for many of the time series measured from each laser system. By mapping the results across an extended parameter space for operation of each laser system, we were able to confidently identify regions of low CD (CD < 3) and assign these robust values for the correlation dimension. However, in all three laser systems, we were not able to measure the correlation dimension at all parts of the parameter space. Nevertheless, by mapping the staged progress of the algorithm, we were able to broadly classify the dynamical output of the lasers at all parts of their respective parameter spaces. For two of the laser systems this included displaying regions of high-complexity chaos and dynamic noise. These high-complexity regions are differentiated from regions where the time series are dominated by technical noise. This is the first time such differentiation has been achieved using a CD analysis approach. CONCLUSIONS: More can be known of the CD for a system when it is interrogated in a mapping context, than from calculations using isolated time series. This has been shown for three laser systems and the approach is expected to be useful in other areas of nonlinear science where large data sets are available and need to be semi-automatically analysed to provide real dimensional information about the complex dynamics. The CD/minimum gradient algorithm measure provides additional information that complements other measures of complexity and relative complexity, such as the permutation entropy; and conventional physical measurements.

Permutation entropy of finite-length white-noise time series.

Permutation entropy (PE) is commonly used to discriminate complex structure from white noise in a time series. While the PE of white noise is well understood in the long time-series limit, analysis in the general case is currently lacking. Here the expectation value and variance of white-noise PE are derived as functions of the number of ordinal pattern trials, N, and the embedding dimension, D. It is demonstrated that the probability distribution of the white-noise PE converges to a χ^{2} distribution with D!-1 degrees of freedom as N becomes large. It is further demonstrated that the PE variance for an arbitrary time series can be estimated as the variance of a related metric, the Kullback-Leibler entropy (KLE), allowing the qualitative N≫D! condition to be recast as a quantitative estimate of the N required to achieve a desired PE calculation precision. Application of this theory to statistical inference is demonstrated in the case of an experimentally obtained noise series, where the probability of obtaining the observed PE value was calculated assuming a white-noise time series. Standard statistical inference can be used to draw conclusions whether the white-noise null hypothesis can be accepted or rejected. This methodology can be applied to other null hypotheses, such as discriminating whether two time series are generated from different complex system states.