Synergistic Biomineralization Phenomena Created by a Combinatorial Nacre Protein Model System.

In the nacre or aragonite layer of the mollusk shell, proteomes that regulate both the early stages of nucleation and nano-to-mesoscale assembly of nacre tablets from mineral nanoparticle precursors exist. Several approaches have been developed to understand protein-associated mechanisms of nacre formation, yet we still lack insight into how protein ensembles or proteomes manage nucleation and crystal growth. To provide additional insights, we have created a proportionally defined combinatorial model consisting of two nacre-associated proteins, C-RING AP7 (shell nacre, Haliotis rufescens) and pseudo-EF hand PFMG1 (oyster pearl nacre, Pinctada fucata), whose individual in vitro mineralization functionalities are well-documented and distinct from one another. Using scanning electron microscopy, flow cell scanning transmission electron microscopy, atomic force microscopy, Ca(II) potentiometric titrations, and quartz crystal microbalance with dissipation monitoring quantitative analyses, we find that both nacre proteins are functionally active within the same mineralization environments and, at 1:1 molar ratios, synergistically create calcium carbonate mesoscale structures with ordered intracrystalline nanoporosities, extensively prolong nucleation times, and introduce an additional nucleation event. Further, these two proteins jointly create nanoscale protein aggregates or phases that under mineralization conditions further assemble into protein-mineral polymer-induced liquid precursor-like phases with enhanced ACC stabilization capabilities, and there is evidence of intermolecular interactions between AP7 and PFMG1 under these conditions. Thus, a combinatorial model system consisting of more than one defined biomineralization protein dramatically changes the outcome of the in vitro biomineralization process.

Assessment of Radiometer Calibration with GPS Radio Occultation for the MiRaTA CubeSat Mission.

The Microwave Radiometer Technology Acceleration (MiRaTA) is a 3U CubeSat mission sponsored by the NASA Earth Science Technology Office (ESTO). The science payload on MiRaTA consists of a tri-band microwave radiometer and Global Positioning System (GPS) radio occultation (GPSRO) sensor. The microwave radiometer takes measurements of all-weather temperature (V-band, 50-57 GHz), water vapor (G-band, 175-191 GHz), and cloud ice (G-band, 205 GHz) to provide observations used to improve weather forecasting. The Aerospace Corporation's GPSRO experiment, called the Compact TEC (Total Electron Content) and Atmospheric GPS Sensor (CTAGS), measures profiles of temperature and pressure in the upper troposphere/lower stratosphere (∼20 km) and electron density in the ionosphere (over 100 km). The MiRaTA mission will validate new technologies in both passive microwave radiometry and GPS radio occultation: (1) new ultra-compact and low-power technology for multi-channel and multi-band passive microwave radiometers, (2) the application of a commercial off the shelf (COTS) GPS receiver and custom patch antenna array technology to obtain neutral atmospheric GPSRO retrieval from a nanosatellite, and (3) a new approach to spaceborne microwave radiometer calibration using adjacent GPSRO measurements. In this paper, we focus on objective (3), developing operational models to meet a mission goal of 100 concurrent radiometer and GPSRO measurements, and estimating the temperature measurement precision for the CTAGS instrument based on thermal noise. Based on an analysis of thermal noise of the CTAGS instrument, the expected temperature retrieval precision is between 0.17 K and 1.4 K, which supports the improvement of radiometric calibration to 0.25 K.

Decision to breastfeed and early cessation of breastfeeding in infants below 6 months old--a population-based study of 3,204 infants in Hong Kong.

Breastfeeding rate has been low in Hong Kong over the last three decades. This has happened with concomitant rapid economic development and improved living standards. A population-based survey was conducted to evaluate factors influencing decision, duration and early cessation of breastfeeding in 3,204 full-term healthy infants under 6 months throughout Hong Kong in 1993. A self-administered questionnaire was used. The overall percentage of breastfed infants was particularly low (9.6%), 36.1%had already given up breastfeeding and were being formula-fed (FFBF), 54.3% have been exclusively formula-fed since birth. The proportion of breastfed infants in the 5th month was even lower than in the 1st month (4.2% vs. 14.7%). Mothers who sustained breastfeeding tended to have parity >or =2, were less educated, housewives and residing in Hong Kong <5 years when compared to FFBF mothers (p<0.009). Husbands had a decisive role on wives initiating breastfeeding while health-professionals had an influence on early switching to FFBF (p<0.003). More breastfeeding mothers perceived breastfeeding benefits than FFBF mothers (p<0.03). The Cox proportional hazard model showed that mother's residency status >or =5-year (HR=2.4), working mothers (HR=1.5) and health-professionals' opinions (HR=1.5) were associated with an early cessation of breastfeeding (p<0.001). However, strengthening immunity (HR=0.67) and parity >or =2 (HR=0.72) helped sustain breastfeeding (p<0.001). To conclude, the proportion of breastfed infants was low in Hong Kong in the early 1990s. Major factors associated with the decision to breastfeed and early cessation of breastfeeding were identified which would help formulate an inter-disciplinary approach for promotion of breastfeeding up-to 6 months and beyond.

A population-based survey on infant feeding practice (0-2 years) in Hong Kong: breastfeeding rate and patterns among 3,161 infants below 6 months old.

The prevalence of breastfeeding for the first 6 months in infants has been low in Hong Kong since the 1970s. In order to develop effective breastfeeding policies and promotion programs, an appraisal of feeding practices and factors related to initiation and early cessation of breastfeeding is necessary. A survey with a population-based representative sample was conducted to determine social-demographic, personal and cultural factors that influenced decision, duration and practice of infant feeding among infants 0-24 months old. This paper focuses on infants below 6 months old to study factors related to decision, duration and practice of breastfeeding. In 1993, 7,298 healthy infants were recruited from 46 Maternal-and-Child-Health-Clinics (MCHC) throughout Hong Kong, of whom 3161 were below 6 months old. The mother reported her feeding decision, duration and practice in a questionnaire. Breastfeeding rate was found to be very low (8.4%) for infants below 6 months old. Only 50.9% infants were breastfed. Infant formulae were widely given among partially breastfed infants. 45% mothers were full-time employed. Most mothers were aware of the benefits of breastfeeding to the infants and themselves. Husbands (43.3%) were regarded the most influential on initiation and duration on breastfeeding. Restricted food varieties (54%), sore nipple and breast engorgement (67%), perceived home confinement (41.5%) and perceived inadequate milk supply (31.7%) were major concerns upon breastfeeding. Furthermore, 76.9% mothers turned to MCHC staff for advice when they encountered difficulties during breastfeeding. In conclusion, the survey collected population-based representative data on factors determining initiation and early cessation of breastfeeding in Hong Kong in 1993. The findings will serve as a cornerstone in understanding the evolution of breastfeeding practice in Hong Kong. It merits further study to investigate how the confounders interplay to modulate initiation, duration and patterns of breastfeeding.