Contaminants in Dietary Supplements: Toxicity, Doping Risk, and Current Regulation.

Athletes, both amateur and professional, often resort to the consumption of nutritional supplements without professional supervision and without being aware of the risks they may entail. We conducted an exhaustive literature search to determine the most common substances found as contaminants in dietary supplements. For each substance, we analyzed its mechanism of action, clinical indication, health risk, and putative use as doping agent. In addition, we evaluated the current regulation of these supplements. Contamination of nutritional supplements (accidental or intentional), especially with steroids and stimulants, is a hazardous situation. The prolonged consumption of these products without being aware of their composition can cause serious health risks and, in the case of professional athletes, a possible sanction for doping.

Hepatitis C screening and detection program in a large population: Epidemiological transition and characterization of the disease.

INTRODUCTION: Chronic hepatitis C (CHC) is considered an important public health challenge. Traditionally identified risk factors have undergone an epidemiological transition where other risk factors have become the main cause of new infections. OBJECTIVE: To describe risk factors associated to hepatitis C positivity through the evaluation of the epidemiological profile in hepatitis-C high-risk populations. METHODS: Cross-sectional study was conducted as part of an HCV screening program in Mexican population. All participants answered an HCV risk-factor questionnaire and took a rapid test (RT). All patients reactive to the test were subject to HCV PCR (polymerase chain reaction) confirmation. A logistic regression model was used to examine associations between HCV infection and risk factors. RESULTS: The study included 297 631 participants that completed a risk factor questionnaire and underwent an HCV rapid test (RT). In total, 12 840 (4.5%) were reactive to RT and 9257 (3.2% of participants) were confirmed as positives by PCR test. Of these, 72.9% had at least one risk factor and 10.8% were in prison. Most common risk factors were history of acupuncture/tattooing/piercing (21%), intravenous drug use (15%) and high-risk sexual practices (12%). Logistic regressions found that having at least one risk factor increased the probability of having an HCV-positive result by 20% (OR = 1.20, 95% CI: 1.15-1.26), compared to the population without risk factors. CONCLUSIONS: We identified 3.2% of HCV-viremic subjects, all associated with risk factors and older age. Screening and diagnosis of HCV in high-risk populations (including underserved populations) should be more efficient.

Dosimetry of the left anterior descending coronary artery in left breast cancer patients treated with postoperative external radiotherapy.

AIM: To evaluate the dose distribution to the left anterior descending (LAD) coronary artery in patients treated with postoperative three-dimensional conformal radiotherapy (3DCRT). BACKGROUND: Postoperative radiotherapy may increase the risk of heart disease, particularly in patients with left-sided breast cancer. Clinical data on doses to the LAD are limited. MATERIALS AND METHODS: Retrospective study of 14 patients who underwent postoperative 3DCRT for left breast cancer in 2014. All data were retrieved from medical records. Means, medians, ranges, and percentages were calculated. RESULTS: The mean dose to the LAD in patients with V25 < 1% was 0.12 cGy. Dmean, Dmax and V25 to the heart were, respectively, 3.7 Gy (range, 0.9-4.18), 40.3 Gy (9.28-62.9), and 1.59 cGy. The mean Dmean and Dmax values in the sample were 9.71 Gy and 33.2 Gy, respectively. The maximum dose to the LAD (D2%) ranged from 3.66 to 53.01 Gy. Due to the spacing of the CT slices (5 mm), it was not possible to completely contour the entire artery. The mean dose to the heart (3.3 Gy) was considered acceptable. CONCLUSIONS: The maximum dose to the LAD was as high as 53 Gy, suggesting an increased risk of cardiac morbidity. This study underscores the value of contouring the LAD and the value of the breath hold technique to reduce maximum cardiac doses. Smaller CT cuts (2.5 mm) can improve contouring. Larger studies with long-term follow up are needed to determine the radiation tolerance dose for the LAD.

Interferometric space-mode multiplexing based on binary phase plates and refractive phase shifters.

A Mach-Zehnder interferometer (MZI) that includes in an arm either a reflective image inverter or a Gouy phase shifter (RGPS) can (de)multiplex many types of modes of a few mode fiber without fundamental loss. The use of RGPSs in combination with binary phase plates for multiplexing purposes is studied for the first time, showing that the particular RGPS that shifts π the odd modes only multiplexes accurately low order modes. To overcome such a restriction, we present a new exact refractive image inverter, more compact and flexible than its reflective counterpart. Moreover, we show that these interferometers remove or reduce the crosstalk that the binary phase plates could introduce between the multiplexed modes. Finally, an experimental analysis of a MZI with both an approximated and an exact refractive image inverter is presented for the case of a bimodal multiplexing. Likewise, it is proven experimentally that a RGPS that shifts π/2 demultiplexes two odd modes which can not be achieved by any image inverter.

Spatial mode multiplexing/demultiplexing by Gouy phase interferometry.

We present a theoretical study about spatial mode multiplexing/demultiplexing (mux/demux) without theoretical losses by means of interferometry with selective control of the Gouy phase of optical beams, that is, Gouy phase interferometry (GPI). Different Gouy phase values can be obtained by inserting appropriate optical systems at each arm of an interferometer. Thus, spatial mode mux/demux operations of strategic interest in optical communications with few-mode optical fibers are implemented by means of constructive interference and regardless of the parity and separability of the optical beams. Consequently, unachievable mux/demux by interferometry based on image inversion methods becomes possible with GPI. This kind of operation can also be interesting for optical sensors, optical metrology, image processing, and so on.

Ion-exchanged binary phase plates for mode multiplexing in graded-index optical fibers.

Few-mode graded-index optical fibers are being increasingly relevant in spatial division multiplexing. Likewise, multi-region binary phase plates are fundamental elements for some mode multiplexing schemes in such optical fibers. In this work, we propose a coupling configuration for mode multiplexing based on collimating-focusing graded-index lenses together with binary phase plates, and calculate, in a fully analytical and quasi-analytical way, the theoretical conversion efficiencies and crosstalks between the fields generated by such plates and the Laguerre-Gaussian modes. These modes describe, directly or by a linear combination of them, the first optical modes of many graded-index optical fibers. The results obtained provide both the illumination conditions of the plates and their optical characteristics. The fabrication of the plates is made by using ion-exchange technology and their optical characterization by beam profilometry. The experimental conversion efficiencies are in agreement with the theoretical results.

SDM transmission of real-time 10GbE traffic using commercial SFP + transceivers over 0.5km elliptical-core few-mode fiber.

We experimentally demonstrate the first few-mode space division multiplexed (SDM) transmission of real-time 10Gb/s Ethernet (10GbE) traffic using commercial small form-factor pluggable SFP + transceivers without coherent detection or multiple input multiple output digital signal processing (MIMO-DSP) over 0.5km elliptical-core few-mode-fiber, achieving <-26dB crosstalk between LP(11e) and LP(11o) modes at 1.3µm.

Chromatic characterization of ion-exchanged glass binary phase plates for mode-division multiplexing.

Mode-division multiplexing (MDM) in few-mode fibers is regarded as a promising candidate to increase optical network capacity. A fundamental element for MDM is a modal transformer to LP modes which can be implemented in a free-space basis by using multiregion phase plates, that is, LP plates. Likewise, several wavelengths have to be used due to wavelength multiplexing purposes, optical amplification tasks, and so on. In this work we show that efficient monolithic binary phase plates for different wavelengths can be fabricated by ion-exchange in glass and used for MDM tasks. We introduce an optical characterization method of the chromatic properties of such phase plates which combines the inverse Wentzel-Kramers-Brillouin (IWKB) together with Mach-Zehnder and Michelson-based interferometric techniques. The interferometric method provides a measurement of the phase step for several wavelengths, which characterizes the chromatic properties of the phase plate. Consequently, it is shown that the IWKB method allows us to design and characterize the phase plates in an easy and fast way.

Ion-exchanged glass binary phase plates for mode-division multiplexing.

Significant efforts are being made to increase optical network capacity in response to ever-growing data traffic. One promising candidate is mode-division multiplexing (MDM) in few-mode fibers. A fundamental element for MDM is a modal transformer. Modal transformation can be implemented in a free-space basis by using multiregion phase plates. In this work, we show that efficient monolithic binary phase plates can be fabricated by ion exchange in glass and used for MDM tasks. We present an optical characterization method of such plates, which is based on a combination of the inverse Wentzel-Kramers-Brillouin (IWKB) method and Mach-Zehnder interferometric techniques. The IWKB method allows us to design and characterize the phase plates in an easy and fast way, whereas interferometry gives us a precise measurement of the phase step. Far-field optical intensities are measured, and a high-quality mode transformation is confirmed.

Mode-division multiplexed transmission with inline few-mode fiber amplifier.

We demonstrate mode-division multiplexed WDM transmission over 50-km of few-mode fiber using the fiber's LP01 and two degenerate LP11 modes. A few-mode EDFA is used to boost the power of the output signal before a few-mode coherent receiver. A 6×6 time-domain MIMO equalizer is used to recover the transmitted data. We also experimentally characterize the 50-km few-mode fiber and the few-mode EDFA.