Patricio Mena

Fetal outcome among pregnancies in natural family planning acceptors: an international cohort study.

This international, multicenter, prospective cohort study examines the outcome of pregnancies associated with aging gametes. Comparing pregnancies conceived at or near the peak mucus phase with those occurring before or after the peak provides a means of evaluating the effect of aging gametes. The outcome criteria are (1) rates of spontaneous abortion, (2) low birth weight, and (3) congenital malformations. Preliminary analysis shows a trend toward increased spontaneous abortion with aging gametes in certain subsets (women with prior pregnancy losses) but no effect on birth weight. Too few method failures have yet been studied to make a definitive statement on congenital malformations.

A calibrated digital sideband separating spectrometer for radio astronomy applications

Dual sideband (2SB) receivers are well suited for the spectral observation of complex astronomical signals over a wide frequency range. They are extensively used in radio astronomy, their main advantages being to avoid spectral confusion and to diminish effective system temperature by a factor 2 with respect to double sideband (DSB) receivers. Using available millimeter-wave analog technology, wideband 2SB receivers generally obtain sideband rejection ratios (SRR) of 10–15 dB, insufficient for a number of astronomical applications. We report here the design and implementation of an FPGA-based sideband separating FFT spectrometer. A 4 GHz analog front end was built to test the design and measure sideband rejection. The setup uses a 2SB front end architecture, except that the mixer outputs are directly digitized before the IF hybrid, using two 8 bit ADCs sampling at 1 GSPS. The IF hybrid is implemented on the FPGA together with a set of calibration vectors that, properly chosen, compensate for the analog front end amplitude and phase imbalances. The calibrated receiver exhibits a sideband rejection ratio in excess of 40 dB for the entire 2 GHz RF bandwidth.

Pregnancy outcome in natural family planning users: cohort and case-control studies evaluating safety

Conceptions involving aging gametes are of relevance to natural family planning (NFP) because women using NFP to avoid pregnancy abstain from intercourse during the fertile time of the cycle. To help verify the safety of pregnancies occurring among NFP practitioners, our group has, since 1986, conducted a large cohort study involving six experienced NFP centers. Timing of conception was determined from NFP charts, in which women recorded days on which intercourse occurred. The number of days from the most probable conception intercourse to probable day of ovulation was first determined, and used as an estimate of the time gametes remained in the genital tract before fertilization. Several studies have already been completed, cohort as well as case-control in nature.1. Spontaneous abortions. Three hundred and sixty-one conceptions occurred during the optimal time (day -1 or 0 relative to ovulation), and of these 33 resulted in spontaneous abortion (9.1%). Five hundred and seven conceptions occurred at non-optimal times during the cycle, and of these 55 resulted in spontaneous abortions (10.9%). These differences were not statistically significant (relative risk 1.19, 95% CI, 0.79-1.80) [1].2. Anomalies. Among 780 singleton births in 868 cohort pregnancies, 24 infants had major anomalies (3.1%) as of the present analysis [2]. This frequency is comparable to the general population. To further assess anomalies we employed a case-control approach. All consecutive births (live and stillborn) weighing 500 g or more taking place in 18 participating South American hospitals were examined for minor and major congential anomalies. Mothers of malformed and control infants did not differ with respect to the reported frequency of NFP use, which overall was 6.3% of the 10 642 mothers interviewed (5277 having a malformed infant; 5371 controls). Of 262 discordant pairs, there were 28 or 10.69% mothers within the Down syndrome case group vs. 16/262 or 6.11% among matched controls [3,4]. The odds ratio was 1.84; 95% CI, 0.99-3.96; however, even this non-significant difference narrowed substantially when adjusted for maternal age (OR, 1.78; 95% CI, 0.84-3.75); parity (OR, 1.68; 95% CI, 0.87-3.24); maternal educational level (OR, 1.71; 95% CI, 0.86-3.44); or all three together (OR, 1.74; 95% CI, 0.83-3.64).Conclusions. Our findings should be reassuring to natural family planning users. The overall rate of spontaneous abortion was not increased in NFP users who became pregnant, nor to date was the rate of anomalies. Any contribution to Down syndrome or abortion due to aging gametes would have to be small.

A broadband Orthomode Transducer for the new ALMA band 2+3 (67–116 GHz)

In this paper we present the design, construction and characterization of a broadband Orthomode Transducer (OMT) for the new Band 2+3 of the Atacama Large Millimeter/Submillimeter Array (ALMA). The term Band 2+3 (67-116 GHz) refers to the recent proposal of covering current Bands 2 and 3 with a single dual-polarization broadband receiver. One of the key components of the future receiver is the polarizer, also known as orthomode transducer (OMT). For this work we have selected the turnstile architecture since it presents low cross polarization leakage in a large wideband. We have obtained an OMT with reflection losses below -15 dB, an isolation between output ports below -26 dB, and a cross polar transmission better than -20 dB.

FPGA-based digital signal processing for the next generation radio astronomy instruments: ultra-pure sideband separation and polarization detection

Field Programmable Gate Arrays (FPGAs) capacity and Analog to Digital Converters (ADCs) speed have largely increased in the last decade. Nowadays we can find one million or more logic blocks (slices) as well as several thousand arithmetic units (ALUs/DSP) available on a single FPGA chip. We can also commercially procure ADC chips reaching 10 GSPS, with 8 bits resolution or more. This unprecedented power of computing hardware has allowed the digitalization of signal processes traditionally performed by analog components. In radio astronomy, the clearest example has been the development of digital sideband separating receivers which, by replacing the IF hybrid and calibrating the system imbalances, have exhibited a sideband rejection above 40dB; this is 20 to 30dB higher than traditional analog sideband separating (2SB) receivers. In Rodriguez et al.,1 and Finger et al.,2 we have demonstrated very high digital sideband separation at 3mm and 1mm wavelengths, using laboratory setups. We here show the first implementation of such technique with a 3mm receiver integrated into a telescope, where the calibration was performed by quasi-optical injection of the test tone in front of the Cassegrain antenna. We also reported progress in digital polarization synthesis, particularly in the implementation of a calibrated Digital Ortho-Mode Transducer (DOMT) based on the Morgan et al. proof of concept.3 They showed off- line synthesis of polarization with isolation higher than 40dB. We plan to implement a digital polarimeter in a real-time FPGA-based (ROACH-2) platform, to show ultra-pure polarization isolation in a non-stop integrating spectrometer.

ALMA band 1 development at Universidad de Chile

The lowest spectroscopic band devised for the Atacama Large Millimeter Array (ALMA), the so-called Band 1, covers the frequency range from 31 to 45 GHz. This band was not implemented during the rst construction phase of the telescope, but will be included during a second ALMA development phase. During the past 4 years our group has been working on the development of technology to cover this band, complying with the demanding ALMA specications. Among the most burdensome challenges are the stringent specications on noise temperature, the large required bandwidth, and the limited space available for this receiver within the ALMA cryostat. In this paper we present some of the technologies we have developed, including the design of key components like horn, lens, ortho-mode transducer, and low noise ampliers. We also present an evaluation of third-party components which can be used in the receiver. The work is used to present a preliminary layout of the Band 1 receiver.

Effects of timing of conception on birth weight and preterm delivery of natural family planning users.

Objective: Various birth defects and untoward perinatal outcomes have been claimed to be associated with pregnancies conceived by gametes aged in vivo before fertilization. Thus, these outcomes were systematically assessed in pregnancies occurring in natural family planning (NFP) users. Our international multicenter cohort study of NFP pregnancies (n = 877) is by far the largest systematic study designed to assess pregnancy outcome and is of sufficient power to allow us to address the concern of low birth weight (< 2500 g) and preterm delivery (< 37 weeks gestation).Study design: In addition to gathering baseline medical data, evaluation was performed at 16 weeks, 32 weeks and at term. Data were collected in a systematic cohort fashion, verified by the five collaborating international recruiting centers, and analyzed by investigators in the US. Most recruiting center principal investigators are obstetrician-gynecologists and, if not, have integral relationships with such specialists. Standard criteria could thus be applied within and among centers. In our cohort, birth weight was recorded accurately at delivery. Almost all of the deliveries occurred in hospitals; thus, data should be quite reliable. Neonatal examination for anomalies was usually conducted immediately after delivery, when birth weight was recorded.Results: Analysis of risk factors for low birth weight and pretern delivery showed that this population had a low risk profile. Low birth weight infants (< 2500 g) and preterm deliveries were increased among women with a history of either prior low birth weight or preeclampsia in the index pregnancy. However, mean birth weight was unaffected by the timing of conception vis à vis ovulation or pregnancy history. Mean birh weight for the 877 singleton NFP pregnancies was 3349.6 g. The risk of preterm delivery was increased among older women who drank alcohol, but there were no significant effects of timing of conception vis à vis ovulation on preterm delivery. Results held when analysis was stratified according to whether NFP was being used for contraception or to achieve pregnancy.Conclusions: Our data do not appear to show striking differences between 877 NFP pregnancies and the general obstetric population. The timing of conception vis à vis ovulation does not exert significant effects on the birth weight or preterm delivery of resulting pregnancies, a reassuring finding for NFP users.