Observation on temperature and strain dependency of Brillouin dynamic grating in a few-mode fiber with a ring-cavity configuration.

We experimentally conduct Brillouin dynamic grating (BDG) operation using a 1-km-long four-mode fiber. By employing a simplified ring-cavity configuration with single-end pumping, the BDG is effectively generated in $ {{\rm LP}_{01}} $LP01 mode within a range of 250 m, and three higher-order modes, namely, $ {{\rm LP}_{11b}} $LP11b, $ {{\rm LP}_{21a}} $LP21a, and $ {{\rm LP}_{02}} $LP02, are chosen as probes to analyze the BDG with a spatial resolution of 1 m. To the best of our knowledge, this is the first time to characterize the responses of BDG frequency to temperature and strain for different modes in a conventional few-mode fiber. By employing the pump-probe pair of $ {{\rm LP}_{01}}{{\rm - LP}_{02}} $LP01-LP02 mode, the highest temperature and strain sensitivities of 3.21 MHz/°C and $ - 0.0384\;{\rm MHz}/{\unicode{x00B5}}{\unicode{x03B5}} $-0.0384MHz/µÎµ have been achieved. Also, the performance of simultaneously distributed temperature and strain sensing based on BDG is evaluated.

Mode-selective few-mode Brillouin fiber lasers based on intramodal and intermodal SBS.

Mode-selective fiber lasers have advantages in a number of applications. Here we propose and experimentally demonstrate a transverse mode-selective few-mode Brillouin fiber laser using the mode-selective photonic lantern. We generated the lowest three orders of linearly polarized (LP) modes based on both intramodal and intermodal stimulated Brillouin scattering (SBS). Their slope efficiencies, optical spectra, mode profiles, and linewidths were measured.

Low-crosstalk few-mode EDFAs using retro-reflection for single-mode fiber trunk lines and networks.

Few-mode EDFAs with low channel crosstalk can replace multiple parallel single-mode EDFAs in single-mode fiber trunk lines and networks. Here we proposed a low-crosstalk few-mode EDFA by exploiting the unitary property of the coupling matrix of a symmetric photonic lantern. We experimentally demonstrated a 3-channel few-mode EDFA using retro-reflection of a 3-mode symmetric photonic lantern. The small signal gain for all three channels are measured to be larger than 25 dB over the entire C-band and the crosstalks are below -10 dB.

HIV-2 as a model to identify a functional HIV cure.

Two HIV virus types exist: HIV-1 is pandemic and aggressive, whereas HIV-2 is confined mainly to West Africa and less pathogenic. Despite the fact that it has been almost 40 years since the discovery of AIDS, there is still no cure or vaccine against HIV. Consequently, the concepts of functional vaccines and cures that aim to limit HIV disease progression and spread by persistent control of viral replication without life-long treatment have been suggested as more feasible options to control the HIV pandemic. To identify virus-host mechanisms that could be targeted for functional cure development, researchers have focused on a small fraction of HIV-1 infected individuals that control their infection spontaneously, so-called elite controllers. However, these efforts have not been able to unravel the key mechanisms of the infection control. This is partly due to lack in statistical power since only 0.15% of HIV-1 infected individuals are natural elite controllers. The proportion of long-term viral control is larger in HIV-2 infection compared with HIV-1 infection. We therefore present the idea of using HIV-2 as a model for finding a functional cure against HIV. Understanding the key differences between HIV-1 and HIV-2 infections, and the cross-reactive effects in HIV-1/HIV-2 dual-infection could provide novel insights in developing functional HIV cures and vaccines.

Control over the transverse structure and long-distance fiber propagation of light at the single-photon level.

Quantum entanglement is arguably the cornerstone which differentiates the quantum realm from its classical counterpart. While entanglement can reside in any photonic degree of freedom, polarization permits perhaps the most straightforward manipulation due to the widespread availability of standard optical elements such as waveplates and polarizers. As a step towards a fuller exploitation of entanglement in other degrees of freedom, in this work we demonstrate control over the transverse spatial structure of light at the single-photon level. In particular we integrate in our setup all the technologies required for: (i) fibre-based photon pair generation, (ii) deterministic and broadband single-photon spatial conversion relying on a passive optical device, and (iii) single-photon transmission, while retaining transverse structure, over 400 m of few-mode fibre. In our experiment, we employ a mode selective photonic lantern multiplexer with the help of which we can convert the transverse profile of a single photon from the fundamental mode into any of the supported higher-order modes. We also achieve conversion to an incoherent or coherent addition of two user-selected higher order modes by addressing different combinations of inputs in the photonic lantern multiplexer. The coherent nature of the addition, and extraction of usable orbital angular momentum at the single-photon level, is further demonstrated by far-field diffraction through a triangular aperture. Our work could enable studies of photonic entanglement in the transverse modes of a fibre and could constitute a key resource quantum for key distribution with an alphabet of scalable dimension.

Long-term follow-up of HIV-2-related AIDS and mortality in Guinea-Bissau: a prospective open cohort study.

BACKGROUND: HIV type 2 (HIV-2) is considered more benign and has fewer pathogenic consequences than HIV type 1 (HIV-1) for most infected individuals. However, reliable estimates of time to AIDS and mortality among those with HIV-2 infection are absent. We therefore aimed to compare the time to AIDS and mortality, and the CD4 T-cell dynamics between those infected with HIV-1 and HIV-2. METHODS: We did a prospective open cohort study. We included all police officers with regular employment from police stations in both urban and rural areas of Guinea-Bissau since Feb 6, 1990. We continued to include participants until Sept 28, 2009, and follow-up of HIV-1-positive and HIV-2-positive individuals continued until Sept 28, 2013. We collected blood samples at enrolment and at scheduled annual follow-up visits at police stations. We analysed longitudinal data from individuals infected with HIV-1 and HIV-2 according to time to AIDS, time to death, and T-cell dynamics. Time of HIV infection was estimated as the mid-timepoint between last HIV-seronegative and first HIV-seropositive sample. Data from an additional 2984 HIV-uninfected individuals from the same population were analysed to assess the effect of natural mortality on HIV-related mortality. FINDINGS: 872 participants tested HIV positive during the 23-year study period: 408 were infected with HIV-1 (183 infected before and 225 infected after enrolment) and 464 were infected with HIV-2 (377 before and 87 after enrolment). The median time from HIV infection to development of AIDS was 6·2 years (95% CI 5·4-7·1) for HIV-1 infection and 14·3 years (10·7-18·0) for HIV-2 infection (p<0·0001). The median survival time after HIV infection was 8·2 years (95% CI 7·5-8·9) for HIV-1 infection and 15·6 years (12·0-19·2) for HIV-2 infection (p<0·0001). Individuals who were infected with HIV-1 or HIV-2 before enrolment showed similar results. Comparison with uninfected individuals indicated limited confounding contribution from natural mortality. Mean CD4 percentages were higher in individuals with HIV-2 than in those with HIV-1 during early infection (28·0% [SE 1·3] vs 22·3% [1·7]; p=0·00094) and declined at a slower rate (0·4% [0·2] vs 0·9% [0·2] per year; p=0·028). HIV-2-infected individuals developed clinical AIDS at higher mean CD4 percentages (18·2%, IQR 7·2-25·4) than HIV-1-infected individuals (8·2%, 3·0-13·8; p<0·0001). INTERPRETATION: Our results show that both HIV-1-infected and HIV-2-infected individuals have a high probability of developing and dying from AIDS without antiretroviral treatment. FUNDING: Swedish International Development Agency, Swedish Research Council, Swedish Society of Medical Research, Medical Faculty at Lund University, and Region Skåne Research and Development.

HIV-2 continues to decrease, whereas HIV-1 is stabilizing in Guinea-Bissau.

OBJECTIVE: Although Guinea-Bissau has the world's highest prevalence of HIV-2, it has been decreasing since 1987. Meanwhile, the prevalence of HIV-1 has been increasing. We describe both the prevalence and changes in incidence of HIV-2 and HIV-1 during the last 30 years of observation in the capital Bissau in Guinea-Bissau. METHODS: A total of 3125 adults living in 412 houses in Bissau were eligible for inclusion in the present cross-sectional survey conducted from November 2014 to February 2016. All participants had a questionnaire filled out and a blood sample taken. Results were compared with previous surveys. RESULTS: Of the 3125 eligible adults, 2601 (83.2%) individuals participated. The overall prevalence of HIV decreased from 8.6% (218/2548) in 2006 to 6.7% (173/2601) in 2016 with an age-adjusted and sex-adjusted prevalence ratio (aPR) of 0.71 [95% confidence interval (CI) = 0.59-0.85]. Including HIV-1/2 dual infections, a decrease in the overall prevalence of HIV-2 from 4.4% (112/2548) to 2.8% (72/2601) was observed with an aPR of 0.55 (95% CI = 0.41-0.73). The overall prevalence of HIV-1 decreased from 4.6% (118/2548) to 4% (104/2601) with an aPR of 0.81 (95% CI = 0.63-1.05). Incidence rates for HIV-2 and HIV-1, estimated for 815 individuals, decreased from 0.24 to 0.09 and from 0.50 to 0.40 per 100 person-years of observation, respectively, in the periods between 1996-2006 and 2006-2016. CONCLUSION: The prevalence of HIV-2 continues to decrease, whereas the prevalence of HIV-1 showed sign of stabilization. The results observed may be explained by a lower pathogenicity of HIV-2 and changes in risk behavior.

Transverse mode-switchable fiber laser based on a photonic lantern.

We propose and experimentally demonstrate an intra-cavity transverse mode-switchable fiber laser based on a mode-selective photonic lantern and a few-mode Er-doped fiber amplifier. The six lowest-order LP modes can lase independently and are switchable by changing the input port of the photonic lantern. We measured the slope efficiency, mode intensity profile, and optical spectrum of each lasing mode. In addition, we demonstrate donut-shaped LP11 and LP21 modes using incoherent superposition and simultaneous lasing of the two degenerate modes.

The Effect of Smallpox and Bacillus Calmette-Guérin Vaccination on the Risk of Human Immunodeficiency Virus-1 Infection in Guinea-Bissau and Denmark.

BACKGROUND: The live smallpox and Bacillus Calmette-Guérin (BCG) vaccinations have been associated with better adult survival in both Guinea-Bissau and Denmark. In Guinea-Bissau, human immunodeficiency virus (HIV)-1 became an important cause of death after smallpox vaccination was phased out globally in 1980. We hypothesised that smallpox and BCG vaccinations were associated with a lower prevalence of HIV-1 infection, and we tested this hypothesis in both Guinea-Bissau and Denmark. METHODS: We conducted 2 studies: (1) a cross-sectional study of HIV infection and vaccination scars in Guinea-Bissau including 1751 individuals and (2) a case-base study with a background population of 46239 individuals in Denmark. In Guinea-Bissau, HIV-1 transmission was almost exclusively sexually transmitted. In Denmark, we excluded intravenous drug users. Data were analyzed using logistic regression. RESULTS: Bacillus Calmette-Guérin and/or smallpox vaccination compared with neither of these vaccines was associated with an adjusted odds ratio (aOR) for HIV-1 of 0.62 (95% confidence interval [CI], 0.36-1.07) in Guinea-Bissau and 0.70 (95% CI, 0.43-1.15) in Denmark. We combined the results from both settings in a meta-analysis (aOR = 0.66; 95% CI, 0.46-0.96). Data from Guinea-Bissau indicated a stronger effect of multiple smallpox vaccination scars (aOR = 0.27; 95% CI, 0.10-0.75) as follows: women, aOR = 0.18 (95% CI, 0.05-0.64); men, aOR = 0.52 (95% CI, 0.12-2.33); sex-differential effect, P = .29. CONCLUSIONS: The studies from Guinea-Bissau and Denmark, 2 very different settings, both suggest that the BCG and smallpox vaccines could be associated with a decreased risk of sexually transmitted HIV-1. It might be informative to pursue this observation and explore possible protective mechanisms as part of the search for an HIV-1 vaccine.

All-fiber few-mode multicore photonic lantern mode multiplexer.

The emergence of space division multiplexing (SDM) for ultrahigh capacity networks has heralded pioneering Petabit-class optical transmission systems. In parallel to novel SDM fibers, a new class of components to enable scalable, low-loss schemes for unlocking fiber capacity is being developed. In this work, an all-fiber mode selective photonic lantern mode multiplexer designed for launching into few-mode multicore fibers is demonstrated. This device is capable of selectively exciting LP01, LP11a and LP11b modes in a seven-core configuration, resulting in 21 spatial channels, with less than 38 dB core-to-core crosstalk and insertion loss below 0.4 dB. The multicore photonic lantern multiplexer is scalable to larger number of cores and modes per core, and can be easily integrated with emerging ultra-high bandwidth few-mode multicore optical communication systems.

Mode-selective amplification in a large mode area Yb-doped fiber using a photonic lantern.

We demonstrate selective spatial mode amplification in a few mode, double-clad Yb-doped large mode area (LMA) fiber, utilizing an all-fiber photonic lantern. Amplification to multi-watt output power is achieved while preserving high spatial mode selectivity. We observe gain values of over 12 dB for all modes: LP01, LP11a, and LP11b, when amplified individually. Additionally, we investigate the simultaneous amplification of LP01+LP11a and LP11a+LP11b, and the resultant mode competition. The proposed architecture allows for the reconfigurable excitation of spatial modes in the LMA fiber amplifiers, and represents a promising method that could enable dynamic spatial mode control in high power fiber lasers.

Predicting the extinction of HIV-2 in rural Guinea-Bissau.

OBJECTIVE: This article predicts the future epidemiology of HIV-2 in Caió, a rural region of Guinea Bissau; and investigates whether HIV-2, which has halved in prevalence between 1990 and 2007 and is now almost absent in young adults in Caió, can persist as an infection of the elderly. DESIGN: A mathematical model of the spread of HIV-2 was tailored to the epidemic in Caió, a village in Guinea-Bissau. METHODS: An age-stratified difference equation model of HIV-2 transmission was fitted to age-stratified HIV-2 incidence and prevalence data from surveys conducted in Caió in 1990, 1997 and 2007. A stochastic version of the same model was used to make projections. RESULTS: HIV-2 infection is predicted to continue to rapidly decline in Caió such that new infections will cease and prevalence will reach low levels (e.g. below 0.1%) within a few decades. HIV-2 is not predicted to persist in the elderly. CONCLUSION: HIV-2 is predicted go extinct in Caió during the second half of this century.

Increased survival among HIV-1 and HIV-2 dual-infected individuals compared to HIV-1 single-infected individuals.

OBJECTIVE: To compare survival times of HIV-1 single and HIV-1 and HIV-2 dual-infected individuals. DESIGN: Prospective open cohort study. METHODS: We analysed data from 259 HIV-1-seroincident cases (either HIV-1 single or HIV-1 and HIV-2 dual-infected) from a cohort with long follow-up (~20 years) in order to study the influence of type of infection and infection order on mortality. Sex and age at HIV-1 infection date was controlled for in a Cox proportional-hazards model. RESULTS: Dual-infected individuals had a 42% longer time from HIV-1 infection to death compared with single-infected individuals, adjusting for age asymmetries between groups. Dual-infected individuals with an HIV-2 infection preceding the HIV-1 infection had a more than two-fold lower mortality risk during follow-up than HIV-1 single-infected individuals. CONCLUSION: Survival time is longer and the risk of progression to death is lower among HIV-1 and HIV-2 dual-infected individuals compared to HIV-1 single-infected individuals. This natural inhibition could have implications for the development of future HIV-1 vaccines and therapeutics.

Assessment of simple risk markers for early mortality among HIV-infected patients in Guinea-Bissau: a cohort study.

BACKGROUND: Decisions about when to start an antiretroviral therapy (ART) are normally based on CD4 cell counts and viral load (VL). However, these measurements require equipment beyond the capacity of most laboratories in low-income and middle-income settings. Thus, there is an urgent need to identify and test simple markers to guide the optimal time for starting and for monitoring the effect of ART in developing countries. OBJECTIVES: (1) To evaluate anthropometric measurements and measurement of plasma-soluble form of the urokinase plasminogen activator receptor (suPAR) levels as potential risk factors for early mortality among HIV-infected patients; (2) to assess whether these markers could help identify patients to whom ART should be prioritised and (3) to determine if these markers may add information to CD4 cell count when VL is not available. DESIGN: An observational study. SETTING: The largest ART centre in Bissau, Guinea-Bissau. PARTICIPANTS: 1083 ART-naïve HIV-infected patients. OUTCOME MEASURES: Associations between baseline anthropometric measurements, CD4 cell counts, plasma suPAR levels and survival were examined using Cox proportional hazards models. RESULTS: Low body mass index (BMI≤18.5 kg/m(2)), low mid-upper-arm-circumference (MUAC≤250 mm), low CD4 cell count (≤350 cells/µl) and high suPAR plasma levels (>5.3 ng/ml) were independent predictors of death. Furthermore, mortality among patients with low CD4 cell count, low MUAC or low BMI was concentrated in the highest suPAR quartile. CONCLUSIONS: Irrespective of ART initiation and baseline CD4 count, MUAC and suPAR plasma levels were independent predictors of early mortality in this urban cohort. These markers could be useful in identifying patients at the highest risk of short-term mortality and may aid triage for ART when CD4 cell count is not available or when there is shortness of antiretroviral drugs.

Inhibition of HIV-1 disease progression by contemporaneous HIV-2 infection.

BACKGROUND: Progressive immune dysfunction and the acquired immunodeficiency syndrome (AIDS) develop in most persons with untreated infection with human immunodeficiency virus type 1 (HIV-1) but in only approximately 20 to 30% of persons infected with HIV type 2 (HIV-2); among persons infected with both types, the natural history of disease progression is poorly understood. METHODS: We analyzed data from 223 participants who were infected with HIV-1 after enrollment (with either HIV-1 infection alone or HIV-1 and HIV-2 infection) in a cohort with a long follow-up duration (approximately 20 years), according to whether HIV-2 infection occurred first, the time to the development of AIDS (time to AIDS), CD4+ and CD8+ T-cell counts, and measures of viral evolution. RESULTS: The median time to AIDS was 104 months (95% confidence interval [CI], 75 to 133) in participants with dual infection and 68 months (95% CI, 60 to 76) in participants infected with HIV-1 only (P=0.003). CD4+ T-cell levels were higher and CD8+ T-cell levels increased at a lower rate among participants with dual infection, reflecting slower disease progression. Participants with dual infection with HIV-2 infection preceding HIV-1 infection had the longest time to AIDS and highest levels of CD4+ T-cell counts. HIV-1 genetic diversity was significantly lower in participants with dual infections than in those with HIV-1 infection alone at similar time points after infection. CONCLUSIONS: Our results suggest that HIV-1 disease progression is inhibited by concomitant HIV-2 infection and that dual infection is associated with slower disease progression. The slower rate of disease progression was most evident in participants with dual infection in whom HIV-2 infection preceded HIV-1 infection. These findings could have implications for the development of HIV-1 vaccines and therapeutics. (Funded by the Swedish International Development Cooperation Agency-Swedish Agency for Research Cooperation with Developing Countries and others.).

Higher mortality in HIV-2/HTLV-1 co-infected patients with pulmonary tuberculosis in Guinea-Bissau, West Africa, compared to HIV-2-positive HTLV-1-negative patients.

OBJECTIVES: To investigate the effect of human T-lymphotropic virus type 1 (HTLV-1) on CD4 counts and mortality in tuberculosis (TB) patients with or without human immunodeficiency virus (HIV). METHODS: A prospective study on 280 hospitalized patients with pulmonary TB was performed in Guinea-Bissau, 1994-1997, including HIV, CD4 counts and clinical outcome. We compared the CD4 count levels at the time of inclusion between HIV-negative and HIV-positive patients, with or without HTLV-1. Mortality was determined while patients were on treatment for TB. RESULTS: Median CD4% was significantly higher in HIV-positive subjects co-infected with HTLV-1 compared to HTLV-1-negative patients. Two hundred thirty-three individuals were included in the analysis of mortality, and among HIV-negative subjects the mortality was 18.6/100 person-years . In HIV-2-positive HTLV-1-negative subjects the mortality was 39.5/100 person-years and in HIV-2/HTLV-1 co-infected patients it was 113.6/100 person-years (adjusted mortality rate ratio 4.7, 95% CI 1.5-14.4; p < 0.01). When all HIV-positive patients were analyzed together, corresponding mortality rates were 53.5/100 person-years and 104.8/100 person-years , respectively (not significant). CONCLUSIONS: HIV/HTLV-1 co-infected patients hospitalized for pulmonary TB had a high mortality and had significantly higher CD4% compared to only HIV-positive subjects. This may imply that HTLV-1 has an adverse effect on the immune system in HIV-infected subjects, independently of the CD4 count, that makes co-infected subjects more vulnerable to TB.

Tuberculosis burden in an urban population: a cross sectional tuberculosis survey from Guinea Bissau.

BACKGROUND: Little is known about the prevalence of pulmonary tuberculosis (TB) in low income countries. We conducted a cross sectional survey for pulmonary TB and TB symptoms in Bissau, Guinea-Bissau, in an urban cohort with known HIV prevalence. TB surveillance in the area is routinely based on passive case finding. METHODS: Two cohorts were selected based on a previous HIV survey, but only 52.5% of those enrolled in the adult cohort had participated in the HIV survey. One cohort included all adults living in 384 randomly selected houses; in this cohort 8% (135/1687) were HIV infected. The other included individuals 50 years or older from all other houses in the study area; of these 11% (62/571) were HIV infected. Symptom screening was done through household visits using a standardised questionnaire. TB suspects were investigated with sputum smear microscopy and X-ray. RESULTS: In the adult cohort, we found 4 cases among 2989 individuals screened, giving a total TB prevalence of 134/100,000 (95% CI 36-342/100,000). In the >50 years cohort, we found 4 cases among 571 individuals screened, giving a total prevalence of 701/100,000 (191-1784/100.000). Two of the eight detected TB cases were unknown by the TB program. Of the total TB cases five were HIV uninfected while three had unknown HIV status. The prevalence of TB symptoms was 2.1% (63/2989) and 10.3% (59/571) in the two cohorts respectively. CONCLUSIONS: In conclusion we found a moderately high prevalence of pulmonary TB and TB symptoms in the general population, higher among elderly individuals. By active case finding unknown cases were detected. Better awareness of TB and its symptoms needs to be promoted in low income settings.

Frequent CXCR4 tropism of HIV-1 subtype A and CRF02_AG during late-stage disease--indication of an evolving epidemic in West Africa.

BACKGROUND: HIV-1 is one of the fastest evolving pathogens, and is distinguished by geographic and genetic variants that have been classified into different subtypes and circulating recombinant forms (CRFs). Early in infection the primary coreceptor is CCR5, but during disease course CXCR4-using HIV-1 populations may emerge. This has been correlated with accelerated disease progression in HIV-1 subtype B. Basic knowledge of HIV-1 coreceptor tropism is important due to the recent introduction of coreceptor antagonists in antiretroviral therapy, and subtype-specific differences regarding how frequently HIV-1 CXCR4-using populations appear in late-stage disease need to be further investigated. To study how frequently CXCR4-using populations appear in late-stage disease among HIV-1 subtype A and CRF02_AG, we evaluated the accuracy of a recombinant virus phenotypic assay for these subtypes, and used it to determine the HIV-1 coreceptor tropism of plasma samples collected during late-stage disease in Guinea-Bissau. We also performed a genotypic analysis and investigated subtype-specific differences in the appearance of CXCR4 tropism late in disease. RESULTS: We found that the recombinant virus phenotypic assay accurately predicted HIV-1 coreceptor tropism of subtype A and CRF02_AG. Over the study period (1997-2007), we found an increasing and generally high frequency of CXCR4 tropism (86%) in CRF02_AG. By sequence analysis of the V3 region of our samples we developed a novel genotypic rule for predicting CXCR4 tropism in CRF02_AG, based on the combined criteria of the total number of charged amino acids and net charge. This rule had higher sensitivity than previously described genotypic rules and may be useful for development of future genotypic tools for this CRF. Finally, we conducted a literature analysis, combining data of 498 individuals in late-stage disease, and found high amounts of CXCR4 tropism for all major HIV-1 subtypes (60-77%), except for subtype C (15%). CONCLUSIONS: The increase in CXCR4 tropism over time suggests an evolving epidemic of CRF02_AG. The results of the literature analysis demonstrate the need for further studies investigating subtype-specific emergence for CXCR4-tropism; this may be particularly important due to the introduction of CCR5-antagonists in HIV treatment regimens.