Fabrication of surface-enhanced Raman spectroscopy substrates using silver nanoparticles produced by laser ablation in liquids.

This research describes the use of surface-enhanced Raman spectroscopy (SERS) substrates based on colloidal silver nanoparticles (AgNPs) produced by laser ablation of silver granules in pure water that are inexpensive, easy to make, and chemically stable. Here, the effects of the laser power, pulse repetition frequency, and ablation duration on the Surface Plasmon Resonance peak of AgNPs solutions, were used to determine the optimal parameters. Also, the effects of the laser ablation time on both ablation efficiency and SERS enhancement were studied. The synthesized AgNPs were characterized by UV-Vis spectrophotometer, Scanning Electron Microscope (SEM), and Raman spectrometer. The Surface Plasmon Resonance peak of AgNP solutions was centered at 404 nm confirming their synthesis and they were noted to be spherical with 34 nm in diameter. Using Raman spectroscopy, they had main bands centered at 196 cm-1 (O = Ag2/Ag-N stretching vibrations), 568 cm-1 (NH out of plane bending); 824 cm-1 (symmetric deformation of the NO2); 1060 cm-1 (NH out of plane bending); 1312 cm-1 (symmetric stretching of NO2); 1538 cm-1 (NH in-plane bending); and 2350 cm-1 (N2 vibrations). Their Raman spectral profiles remained constant within the first few days of storage at room temperature implying chemical stability. The Raman signals from blood were enhanced when mixed with AgNPs and this depended on colloidal AgNPs concentration. Using those generated by 12 h ablation time, an enhancement of 14.95 was achieved. Additionally, these substrates had an insignificant impact on the Raman profiles of samples of rat blood when mixed with them. The Raman peaks noted were attributed to CC stretching of glucose (932 cm-1); CC stretching of Tryptophan (1064 cm-1); CC stretching of ß Carotene (1190 cm-1); CH2 wagging of proteins (1338 and 1410 cm-1); carbonyl stretch for proteins (1650 cm-1); CN vibrations for glycoproteins (2122 cm-1). These SERS substrates can be applied to areas such as forensics to distinguish between human and other animal blood, monitoring of the efficacy of drugs, disease diagnostics such as diabetes, and pathogen detection. All this can be achieved by comparing the Raman spectra of the biological samples mixed with the synthesized SERS substrates for different samples. Thus, the results on the use of inexpensive, simple-to-prepare Raman substrates have the possibility of making surface-enhanced Raman spectroscopy available to laboratories with scarce resources in developing nations.

Deeply Virtual Compton Scattering Cross Section at High Bjorken x_{B}.

We report high-precision measurements of the deeply virtual Compton scattering (DVCS) cross section at high values of the Bjorken variable x_{B}. DVCS is sensitive to the generalized parton distributions of the nucleon, which provide a three-dimensional description of its internal constituents. Using the exact analytic expression of the DVCS cross section for all possible polarization states of the initial and final electron and nucleon, and final state photon, we present the first experimental extraction of all four helicity-conserving Compton form factors (CFFs) of the nucleon as a function of x_{B}, while systematically including helicity flip amplitudes. In particular, the high accuracy of the present data demonstrates sensitivity to some very poorly known CFFs.

TB testing in HIV-positive patients prior to antiretroviral treatment.

BACKGROUND: TB diagnosis in patients with HIV is challenging due to the lower sensitivities across tests. Molecular tests are preferred and the Xpert® MTB/RIF assay has limitations in lower-income settings. We evaluated the performance of loop-mediated isothermal amplification (LAMP) and the lipoarabinomannan (LAM) test in HIV-positive, ART-naïve clinic patients.METHODS: A total of 783 eligible patients were enrolled; three spot sputum samples of 646 patients were tested using TB-LAMP, Xpert, smear microscopy and culture, while 649 patients had TB-LAM testing. Sensitivity, specificity, and negative and positive predictive values were estimated with 95% confidence intervals.RESULTS: Sensitivities for smear microscopy, TB-LAMP and Xpert were respectively 50%, 63% and 74% compared to culture, with specificities of respectively 99.2%, 98.5% and 97.5%. An additional eight were positive on TB-LAM alone. Seventy TB patients (9%) were detected using standard-of-care testing, an additional 27 (3%) were detected using study testing. Treatment was initiated in 57/70 (81%) clinic patients, but only in 56% (57/97) of all those with positive TB tests; 4/8 multidrug-resistant samples were detected using Xpert.CONCLUSION: TB diagnostics continue to miss cases in this high-burden setting. TB-LAMP was more sensitive than smear microscopy, and if followed by culture and drug susceptibility testing as required, can diagnose TB in HIV-positive patients. TB-LAM is a useful add-in test and both tests at the point-of-care would maximise yield.

Deep Exclusive Electroproduction of π

We report measurements of the exclusive neutral pion electroproduction cross section off protons at large values of x_{B} (0.36, 0.48, and 0.60) and Q^{2} (3.1 to 8.4 GeV^{2}) obtained from Jefferson Lab Hall A experiment E12-06-014. The corresponding structure functions dσ_{T}/dt+εdσ_{L}/dt, dσ_{TT}/dt, dσ_{LT}/dt, and dσ_{LT^{'}}/dt are extracted as a function of the proton momentum transfer t-t_{min}. The results suggest the amplitude for transversely polarized virtual photons continues to dominate the cross section throughout this kinematic range. The data are well described by calculations based on transversity generalized parton distributions coupled to a helicity flip distribution amplitude of the pion, thus providing a unique way to probe the structure of the nucleon.

Laboratory comparison of stool processing methods for Xpert® Ultra.

TB disease diagnosis in children is difficult due to non-specific symptoms, paucibacillary disease and the need for invasive procedures to obtain diagnostic specimens. In many settings, these specimens are simply not collected and therefore stool, easily obtained, has emerged as a promising specimen for the diagnosis of child TB. In this study, stool from a healthy adult was spiked with known concentrations of bacille Calmette-Guérin vaccine and tested using the Xpert® Ultra assay to determine the relative detection and error rate associated with four different published stool processing methods.

Le diagnostic de TB maladie chez l'enfant est difficile en raison de la non spécificité de symptômes, de son caractère paucibacillaire et du besoin de procédures invasives pour obtenir des échantillons diagnostiques. Dans de nombreux contextes, ces échantillons ne sont tout simplement pas recueillis ; c'est pourquoi les selles, faciles à obtenir, sont apparus comme un échantillon prometteur pour le diagnostic de la TB de l'enfant. Dans cette étude, des selles d'un adulte en bonne santé ont été enrichies avec des concentrations connues de vaccin Bacille Calmette-Guérin et testés avec le test Xpert Ultra pour déterminer les taux relatifs de détection et d'erreur associés à quatre différentes méthodes publiées de traitement des selles.

Ruling out Color Transparency in Quasielastic

Quasielastic ^{12}C(e,e^{'}p) scattering was measured at spacelike 4-momentum transfer squared Q^{2}=8, 9.4, 11.4, and 14.2 (GeV/c)^{2}, the highest ever achieved to date. Nuclear transparency for this reaction was extracted by comparing the measured yield to that expected from a plane-wave impulse approximation calculation without any final state interactions. The measured transparency was consistent with no Q^{2} dependence, up to proton momenta of 8.5 GeV/c, ruling out the quantum chromodynamics effect of color transparency at the measured Q^{2} scales in exclusive (e,e^{'}p) reactions. These results impose strict constraints on models of color transparency for protons.

Probing the Deuteron at Very Large Internal Momenta.

We measure ^{2}H(e,e^{'}p)n cross sections at 4-momentum transfers of Q^{2}=4.5±0.5 (GeV/c)^{2} over a range of neutron recoil momenta p_{r}, reaching up to ∼1.0 GeV/c. We obtain data at fixed neutron recoil angles θ_{nq}=35°, 45°, and 75° with respect to the 3-momentum transfer q[over →]. The new data agree well with previous data, which reached p_{r}∼500 MeV/c. At θ_{nq}=35° and 45°, final state interactions, meson exchange currents, and isobar currents are suppressed and the plane wave impulse approximation provides the dominant cross section contribution. We compare the new data to recent theoretical calculations, where we observe a significant discrepancy for recoil momenta p_{r}>700 MeV/c.

Detecting Mycobacterium tuberculosis using the loop-mediated isothermal amplification test in South Africa.

SETTING: In South Africa, KwaZulu-Natal is the epicentre of the human immunodeficiency virus (HIV) epidemic, where approximately 70% of people with tuberculosis (TB) are co-infected with HIV. Undiagnosed TB contributes to high mortality in HIV-infected patients. Delays in diagnosing TB and treatment initiation result in prolonged transmission and increased infectiousness. OBJECTIVE: To evaluate the LoopampTM MTBC Detection kit (TB-LAMP; based on the loop-mediated isothermal amplification assay), smear microscopy and Xpert test with the gold standard of mycobacterial culture. METHODS: Sputum samples were collected from 705 patients with symptoms of pulmonary TB attending a primary health care clinic. RESULTS: The TB-LAMP assay had significantly higher sensitivity than smear microscopy (72.6% vs. 45.4%, P < 0.001), whereas specificity was slightly lower (99% vs. 96.8%, P = 0.05), but significantly higher than Xpert (92.9%, P = 0.004). There was no significant difference in sensitivity of smear-positive, culture-positive and smear-negative, culture-positive sputum samples using TB-LAMP vs. Xpert (respectively 95.9%/55.9% vs. 97.6%/66.1%; P =0.65, P = 0.27). The positive predictive value of TB-LAMP was significantly higher than that of Xpert (87.5% vs. 77.0%; P = 0.02), but similar to that of smear microscopy (94.2%; P = 0.18). The negative predictive value was respectively 91.9%, 92.5% (P = 0.73) and 83.1% (P = 0.0001). CONCLUSION: Given its ease of operability, the TB-LAMP assay could be implemented as a point-of-care test in primary health care settings, and contribute to reducing treatment waiting times and TB prevalence.

Nurse-managed care for health care workers in southern Africa.

In Swaziland, the health care system is experiencing severe scarcity of health care workers (HCWs) due to difficult working conditions, migration and the human immunodeficiency virus (HIV) pandemic. Nurses and other HCWs in Swaziland are personally as affected by communicable diseases as the general population. High levels of HIV and TB co-infection bring added complexity to care. The loss of skilled staff in key positions has had a particularly negative impact on the quality of care and service delivery. The Swaziland Nurses Association (SNA) has established a Centre for Comprehensive Wellness for HCWs in the public and private sector and their immediate families to support the health workforce.

First report of cryptosporidiosis in paediatric patients in Swaziland.

Diarrhoeal disease is a significant cause of morbidity and mortality in many African countries, especially among the immunocompromised and the under five population. Over the last decade, the protozoan parasite Cryptosporidum spp. has been shown to be a significant cause of gastro-enetritis in the immunocompetent and immunocompromised in both the developed and developing world. This study reports the first finding of Cryptosporidum spp. oocysts in 2 of 48 (4.2%) faecal samples obtained from Swazi paediatric outpatients (two year old male and three year old female), presenting with diarrhoea at Mbabane Government Hospital between the months July-August 2003. Oocysts were detected using a standard anti-Cryptosporidium immunofluorescence and nuclear staining technique (after formal-ether concentration). Oocysts ranged in size from 4-6 microm with between 1-4 oocysts per field of view (x 400). The precise species was not determined. Further studies are required to determine the public health significance of Cryptospoirdium in Swaziland.

Syphilis in Swaziland: a serological survey.

Sera from 536 adults and children in Swaziland were examined for their reactivity in the rapid plasma reagin (RPR) and Treponema pallidum haemagglutination (TPHA) tests. None of 130 sera from children was reactive in either test; 8.6% of sera from 185 healthy adults were reactive in the RPR test and 33% in the TPHA test; 24.5% of 220 sera from patients with genital ulcers were RPR-positive and 45.9% TPHA-positive. The RPR positivity rates were not related to age, but the percentage of RPR-negative, TPHA-positive sera increased with age in both the healthy adults and the patients with genital ulcers. Thus venereal syphilis appears to be responsible for these high positivity rates. Estimates of the yearly incidence of syphilis are identical for both groups--approximately 1.4%, an unusually high figure.

Epidemiology and aetiology of urethritis in Swaziland.

The annual incidence of urethritis can be estimated to be at lest 3750 per 100,000 population in Swaziland. In a study of 109 males with symptomatic urethritis 80% had gonorrhoea, 6% non-gonococcal urethritis (ngu) and 14% were classified as having no 'objective' urethritis (less than 5 polymorphonuclear leucocytes per highpower field in the urethral smear). The relative frequency of gonorrhoea was 80 to 95% and of non-gonococcal urethritis 5 to 20 according to which criteria are used for patient selection and/or diagnosis of ngu. Chlamydia trachomatis was cultured in 3.4% of the cases with urethritis, comprising one positive culture in 70 patients with gonorrhoea, one in 5 with ngu, and one in 12 with no 'objective' urethritis. Seventy-one percent of patients, with a comparable percentage in each diagnostic group, had chlamydial antibodies when tested by the micro immunofluorescence test to pooled chlamydial antigens. Interpretation of the chlamydial serologic results indicates that lymphogranuloma venereum is probably endemic in the country, and that oculogenital chlamydial infections are not a problem; this corresponds with the low isolation rate of Chlamydia trachomatis in the urethritis cases. The study shows that the epidemiology and causes of urethritis are clearly of a different pattern to that seen in industrialised countries. This type of study is a sound basis for a simplified but effective urethritis control programme which can be implemented in the para-urban and rural health centres in developing countries.