Detailed investigation of self-imaging in large-core multimode optical fibers for application in fiber lasers and amplifiers

Properties of the self-imaging effect based on multimode interference (MMI) in large-core passive optical fibers are investigated and analyzed in detail, with the purpose of using multimode active fibers for high power single-transverse-mode emission. Although perfect self-imaging of the input field from a standard single-mode fiber (SMF-28) in a multimode fiber becomes practically impossible as its core diameter is larger than 50 microm, a quasi-reproduction of the input field occurs when the phase difference between the excited modes and the peak mode inside the multimode fiber is very small. Our simulation and experimental results indicate that, if the length of the multimode fiber segment can be controlled accurately, reproduction of the input field with a self-imaging quality factor larger than 0.9 can be obtained. In this case, a low-loss hybrid fiber cavity composed of a SMF-28 segment and a very-large-core active multimode fiber segment can be built. It is also found that for the hybrid fiber cavity, increasing the mode-field diameter of the single-mode fiber improves both the self-imaging quality and the tolerance on the required length accuracy of the multimode fiber segment. Moreover, in this paper key parameters for the design of MMI-based fiber devices are defined and their corresponding values are provided for multimode fibers with core diameters of 50 microm and 105 microm.

Therapeutic effects on experimental metastatic tumor-bearing mice by vaccination with GM-CSF gene-modified and tumor antigen-pulsed macrophages

Macrophages, with potent cytotoxic and antigen-presenting activities, can be used in cancer treatment. The biological characteristics and antitumor effect of GM-CSF gene-modified and tumor antigen-pulsed macrophages were investigated. The high levels of GM-CSF could be detected in the supernatants of macrophages after gene transfer. The cytotoxicity and the expression of MHC class II molecules of the gene-modified macrophages increased significantly and the antigen-presenting ability was enhanced. The gene-modified macrophages were then pulsed with tumor antigen and used to treat the experimental pulmonary metastastic mice. The number of pulmonary metastases was reduced significantly and the cytotoxicity of the CTL induced from the splenocytes of the tumor-bearing mice also increased. The results demonstrated that adenovirus-mediated GM-CSF gene transfer can activate macrophages to some extent and GM-CSF gene-modified, antigen-pulsed macrophages may be a new type of effective effector cells in the immunogene therapy of cancer.

Using linkage analysis to identify quantitative trait loci for sleep apnea in relationship to body mass index

To understand the genetics of sleep apnea, we evaluated the relationship between the apnea hypopnea index (AHI) and body mass index (BMI) through linkage analysis to identify genetic loci that may influence AHI and BMI jointly and AHI independent of BMI. Haseman-Elston sibling regression was conducted on AHI, AHI adjusted for BMI and BMI in African-American and European-American pedigrees. A comparison of the magnitude of linkage peaks was used to assess the relationship between AHI and BMI. In EAs, the strongest evidence for linkage to AHI was on 6q23-25 and 10q24-q25, both decreasing after BMI adjustment, suggesting loci with pleiotropic effects. Also, a promising area of linkage to AHI but not BMI was observed on 6p11-q11 near the orexin-2 receptor, suggesting BMI independent pathways. In AAs the strongest evidence of linkage for AHI after adjusting for BMI was on chromosome 8p21.3 with linkage increasing after BMI adjustment and on 8q24.1 with linkage decreasing after BMI adjustment. Novel linkage peaks were also observed in AAs to both BMI and AHI on chromosome 13 near the serotonin-2a receptor. These analyses suggest genetic loci for sleep apnea that operate both independently of BMI and through BMI-related pathways.

Highly discordant T cell responses in individuals with recent exposure to household tuberculosis

BACKGROUND

There are limited data comparing interferon-gamma release assays (IGRAs) for the detection of Mycobacterium tuberculosis infection in highly endemic settings.

METHODS

A cross-sectional household contact study was conducted to measure the agreement of two IGRAs in relation to the tuberculin skin test (TST) to detect M tuberculosis infection and to assess the influence of M tuberculosis exposure and age.

RESULTS

In 82 individuals in household contact, 93% of children and 42% of adults had a high M tuberculosis contact score. The TST was positive in 78% of adults and 54% of children, the T-SPOT.TB was positive in 89% of children and 66% of adults and the QuantiFERON TB Gold (QTF) was positive in a similar proportion of adults and children (38.1% and 39.6%). In children there was poor agreement between the TST and T-SPOT.TB (kappa = -0.15) and the T-SPOT.TB and the QTF (kappa = -0.03), but good agreement between the TST and the QTF (kappa = 0.78) using 10 mm cut-off. In adults there was fair to moderate agreement between the TST and T-SPOT.TB (kappa = 0.38), the TST and QTF (kappa = 0.34) and T-SPOT.TB and QTF (kappa = -0.50). High levels of exposure to M tuberculosis were associated with at least a sevenfold odds of being T-SPOT.TB positive (95% CI 7.67 to 508.69) and a threefold odds of being QTF positive (95% CI 3.02 to 30.54). There was a significant difference in the magnitude of T-SPOT.TB early secretory antigenic target (ESAT)-6 and culture filtrate protein 10 kD (CFP-10) spot counts between adults and children.

CONCLUSIONS

The T-SPOT.TB may be more sensitive than the TST or QTF for detecting recent M tuberculosis infection in children. Differences between assays and the predictive utility of these findings for subsequent disease development should be prospectively assessed.

Circumcision and human papillomavirus infection in men: a site-specific comparison

BACKGROUND

Lack of circumcision has been identified as a risk factor for male genital human papillomavirus (HPV) infection, although this association has not been consistently supported.

METHODS

Specimens for HPV testing were collected from a cohort of 379 (primarily heterosexual) adult males. HPV prevalence in the glans penis and coronal sulcus, penile shaft, scrotum, semen, and urine was compared by circumcision status.

RESULTS

Overall, HPV DNA prevalence ranged from 6% in semen to 52% in the penile shaft. The prevalence of any HPV infection in the glans/corona was significantly higher in uncircumcised men (46%) than in circumcised men (29%) (odds ratio [OR], 1.96 [95% confidence interval (CI), 1.02-3.75], adjusted for demographic characteristics and sexual history). Uncircumcised men also had an increased risk of oncogenic HPV infection (adjusted OR, 2.51 [95% CI, 1.11-5.69]) and infection with multiple HPV types (adjusted OR, 3.56 [95% CI, 1.50-8.50]). Among uncircumcised men, HPV prevalence in the foreskin (44%) was comparable to that in the glans/corona, and type-specific positivity was observed between the 2 sites (kappa=0.52).

CONCLUSIONS

Uncircumcised men have an increased risk of HPV infection, including with oncogenic HPV, specifically localized to the glans/corona, possibly because of its proximity to the foreskin, which may be particularly vulnerable to infection.

Neuronal death and survival under oxidative stress in Alzheimer and Parkinson diseases

Neuronal death is a common feature in neurodegenerative diseases including Alzheimer disease (AD) and Parkinson disease (PD). This occurs over years, not the minutes of classically defined apoptosis, and neurons show both responses of apoptosis and regeneration, evidenced by accumulated oxidative insult and attempts at cell cycle re-entry. There is recent evidence suggesting that several known gene mutations in causing familial AD (amyloid beta protein precursor, presenilin-1, or presenilin-2 gene) and familial PD (Parkin, PINK-1, or DJ-1 gene) are associated with increased oxidative stress. Also, several known genetic (e.g. Apolipoprotein Eepsilon4 variant) and environmental (e.g. metals or pesticides exposure) risk factors of sporadic AD and/or PD are associated with increased oxidative stress. In concord, patients at the preclinical stages of AD and PD as well as cellular and animal models of the diseases provide consistent evidence that oxidative insult is a significant early event in the pathological cascade of AD and PD. In contrast to the general aspects of the pathological hallmarks, aggregation of the disease-specific proteins such as amyloid-beta, tau, and alpha-synuclein may act as a compensatory (survival) response against the oxidative insult via the mechanism that the disease-specific structures sequester redox-active metals. Expanding knowledge of the molecular mechanisms of organism longevity indicates that pro-longevity gene products such as forkhead transcription factors and sirtuins are involved in the insulin-like signaling pathway and oxidative stress resistance against aging. An enhancement of the pro-longevity signaling (e.g. caloric restriction) may be a promising approach as anti-oxidative strategy against age-associated neurodegenerative diseases.

Single-transverse-mode output from a fiber laser based on multimode interference

An alternative original approach to achieve single-transverse-mode laser emissions from multimode (MM) active fibers is demonstrated. The fiber cavity is constructed by simply splicing a conventional passive single-mode fiber (SMF-28) onto a few centimeters-long active MM fiber section whose length is precisely controlled. Owing to the self-imaging property of multimode interference (MMI) in the MM fiber, diffraction-limited laser output is obtained from the end of the SMF-28, and the MMI fiber laser is nearly as efficient as the corresponding MM fiber laser. Moreover, because of the spectral filtering effect during in-phase MMI, the bandwidth of the MMI fiber laser is below 0.5 nm.