Development of a bio-inspired optical system that mimics accommodation and lighting regulation like the human eye.

Bio-inspired optical systems have recently been developed using polarizers and liquid or rigid lenses. In this work, we propose a bio-inspired opto-mechatronic system that imitates the accommodation and regulation of light intensity as the human eye does. The system uses a polymeric lens as a cornea, an adjustable diaphragm as an iris, a tunable solid elastic lens as a crystalline lens, and a commercial sensor as a retina. We also present the development of the electronic control system to accommodate and regulate the amount of light that enters the system, for which two stepper motors, an Arduino control system, and light and movement sensors are used. The characterization of the system is presented together with the results obtained, where it can be seen that the system works in an acceptable range as the human eye does.

Metabolism in a deep hypertrophic aquatic ecosystem with high water-level fluctuations: a decade of records confirms sustained net heterotrophy.

Long-term and seasonal changes in production and respiration were surveyed in the Valle de Bravo reservoir, Mexico, in a period during which high water-level fluctuations occurred (2006-2015). We assessed the community metabolism through oxygen dynamics in this monomictic water-body affected by strong diurnal winds. The multiple-year data series allowed relationships with some environmental drivers to be identified, revealing that water level-fluctuations strongly influenced gross primary production and respiratory rates. Production and respiration changed mainly vertically, clearly in relation to light availability. Gross primary production ranged from 0.15 to 1.26 gO2 m-2 h-1, respiration rate from -0.13 to -0.83 gO2  m-2 h-1 and net primary production from -0.36 to 0.66 gO2  m-2 h -1 within the production layer, which had a mean depth of 5.9 m during the stratification periods and of 6.8 m during the circulations. The greater depth of the mixing layer allowed the consumption of oxygen below the production layer even during the stratifications, when it averaged 10.1 m. Respiration below the production layer ranged from -0.23 to -1.38 gO2 m-2 h-1. Vertically integrated metabolic rates (per unit area) showed their greatest variations at the intra-annual scale (stratification-circulation). Gross primary production and Secchi depth decreased as the mean water level decreased between stratification periods. VB is a highly productive ecosystem; its gross primary production averaged 3.60 gC m-2 d-1 during the 10 years sampled, a rate similar to that of hypertrophic systems. About 45% of this production, an annual average net carbon production of 599 g C m-2 year-1, was exported to the hypolimnion, but on the average 58% of this net production was recycled through respiration below the production layer. Overall, only 19% of the carbon fixed in VB is buried in the sediments. Total ecosystem respiration rates averaged -6.89 gC  m-2 d-1 during 2006-2015, doubling the gross production rates. The reservoir as a whole exhibited a net heterotrophic balance continuously during the decade sampled, which means it has likely been a net carbon source, potentially releasing an average of 3.29 gC m-2 d-1 to the atmosphere. These results are in accordance with recent findings that tropical eutrophic aquatic ecosystems can be stronger carbon sources than would be extrapolated from temperate systems, and can help guide future reassessments on the contribution of tropical lakes and reservoirs to carbon cycles at the global scale. Respiration was positively correlated with temperature both for the stratification periods and among the circulations, suggesting that the contribution of C to the atmosphere may increase as the reservoirs and lakes warm up owing to climate change and as their water level is reduced through intensification of their use as water sources.

Phase shifting interferometry using a spatial light modulator to measure optical thin films.

This work describes a process for measuring thin film steps, using phase shifting interferometry (PSI). The phase shifts are applied only in the region where the thin film steps are located. The phase shift is achieved by displaying different gray levels on a spatial light modulator (SLM Holoeye LC2012) placed in one arm of a Twyman-Green (T-G) interferometer. Before measuring the thin film steps, it was necessary to quantify the phase shifts achieved with this SLM by measuring the fringe shifts in experimental interferograms. The phase shifts observed in the interference patterns were produced by displaying the different gray levels on the SLM one by one, from 0 to 255. The experimental interferograms and the thicknesses of the thin film steps were successfully quantified, proving that this method can be used to measure thin films by applying the PSI method only on the region occupied by them.

Community metabolism in a deep (stratified) tropical reservoir during a period of high water-level fluctuations.

As long as lakes and reservoirs are an important component of the global carbon cycle, monitoring of their metabolism is required, especially in the tropics. In particular, the response of deep reservoirs to water-level fluctuations (WLF) is an understudied field. Here, we study community metabolism through oxygen dynamics in a deep monomictic reservoir where high WLF (~10 m) have recently occurred. Simultaneous monitoring of environmental variables and zooplankton dynamics was used to assess the effects of WLF on the metabolism of the eutrophic Valle de Bravo (VB) reservoir, where cyanobacteria blooms are frequent. Mean gross primary production (P g) was high (2.2 g C m(-2) day(-1)), but temporal variation of P g was low except for a drastic reduction during circulation attributed to zooplankton grazing. The trophogenic layer showed net autotrophy on an annual basis, but turned to net heterotrophy during mixing, and furthermore when the whole water-column oxygen balance was calculated, considering the aphotic respiration (Raphotic). The high total respiration resulting (3.1 g C m(-2) day(-1)) is considered to be partly due to mixing enhanced by WLF. Net ecosystem production was equivalent to a net export of 3.4 mg CO2 m(-2) day(-1) to the atmosphere. Low water levels are posed to intensify boundary-mixing events driven by the wind during the stratification in VB. Long-term monitoring showed changes in the planktonic community and a strong silicon decrease that matched with low water-level periods. The effects of low water-level on metabolism and planktonic community in VB suggest that water-level manipulation could be a useful management tool to promote phytoplankton groups other than cyanobacteria.

An alternative hemostatic dressing: comparison of CELOX, HemCon, and QuikClot.

OBJECTIVES: Uncontrolled hemorrhage remains a leading cause of traumatic death. Several topical adjunct agents have been shown to be effective in controlling hemorrhage, and two, chitosan wafer dressing (HemCon [HC]) and zeolite powder dressing (QuikClot [QC]), are being utilized regularly on the battlefield. However, recent literature reviews have concluded that no ideal topical agent exists. The authors compared a new chitosan granule dressing (CELOX [CX]) to HC, QC and standard dressing in a lethal hemorrhagic groin injury. METHODS: A complex groin injury with transection of the femoral vessels and 3 minutes of uncontrolled hemorrhage was created in 48 swine. The animals were then randomized to four treatment groups (12 animals each). Group 1 included standard gauze dressing (SD); Group 2, CX; Group 3, HC; and Group 4, QC. Each agent was applied with 5 minutes of manual pressure followed by a standard field compression dressing. Hetastarch (500 mL) was infused over 30 minutes. Hemodynamic parameters were recorded over 180 minutes. Primary endpoints included rebleed and death. RESULTS: CX reduced rebleeding to 0% (p < 0.001), HC to 33% (95% CI = 19.7% to 46.3%, p = 0.038), and QC to 8% (95% CI = 3.3% to 15.7%, p = 0.001), compared to 83% (95% CI = 72.4% to 93.6%) for SD. CX improved survival to 100% compared to SD at 50% (95% CI = 35.9% to 64.2%, p = 0.018). Survival for HC (67%) (95% CI = 53.7% to 80.3%) and QC (92%; 95% CI = 84.3% to 99.7%) did not differ from SD. CONCLUSIONS: In this porcine model of uncontrolled hemorrhage, CX improved hemorrhage control and survival. CELOX is a viable alternative for the treatment of severe hemorrhage.

Congenital dermoid cyst of the anterior fontanel in mestizo-mulatto children.

OBJECTS: Twenty-seven cases of histologically confirmed congenital dermoid cysts of the anterior fontanel in children are reported. METHODS: The age, sex and race of each patient was recorded. CONCLUSIONS: Ages ranged between 2 months and 6 years. There was a female predominance, and 77.7% of these patients were children of mixed race. Surgical excision resulted in complete cure without complications or recurrences.