The conundrum of unmeasured confounding: Comment on: "Can some of the detrimental neurodevelopmental effects attributed to lead be due to pesticides? by Brian Gulson"

The problem described by Dr. Brian Gulson - confounding by unmeasured exposures to pesticides - is only the most recent in a series of potential confounders cited to explain the observed effect of lead on children's intellectual abilities or behavioral problems. Despite the persistent problem of unmeasured confounders, there are several lines of evidence implicating lead as a toxicant at blood lead levels <10 microg/dL. First, in striking contrast with pesticides, there is considerable evidence from numerous studies linking low-level lead exposure with cognitive deficits and behavioral problems, even after controlling for a variety of potential confounders. Second, the consistency of evidence from diverse cohorts and distinct, if not always directly measured potential confounders - enhances our confidence that the lead effect observed at blood lead levels <10 microg/dL is not attributable to unmeasured confounders. Third, in our reanalysis of the Rochester Lead Study, the inclusion of parent-reported mouthing behaviors and breastfeeding status did not attenuate the effect of lead exposure on children's intellectual function. Finally, although we can never entirely dismiss unmeasured confounding in observational studies, we can rely on experimental studies of lead-exposed animals to confirm that lead is a toxicant. Thus, while we must remain vigilant for unmeasured or poorly measured confounders, it is crucial to balance the endless search for confounders with the evidence of toxicity and the need to take action to protect public health. The alternative, to perpetually permit children to be exposed to lead and other emerging toxicants, is both absurd and unacceptable.     

FLATCON® CPV module with 36.7% efficiency equipped with four‐junction solar cells

In this paper we present the application of high efficiency four‐junction solar cells using SOITEC bonding technology under a Fresnel lens optic and in a FLATCON®‐type CPV module. We demonstrate very high performance. The measurement of a sub‐module, consisting of a four‐junction solar cell adjusted under a single Fresnel lens, showed an efficiency of 38.9%. An 829.6 cm² sized FLATCON®‐type CPV module yielded in an efficiency of 35.0% and 36.7% at CSOC and CSTC, respectively. Thus, both, the sub‐module and the CPV module showed record values, which prove the usefulness of high efficiency four‐junction solar cells in CPV applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Contact and proximity lithography using 193 nm Excimer laser in Mask Aligner

In this paper we describe the use of an Excimer laser for full-field lithography in a Mask Aligner. The DUV light from the Excimer laser is homogenized by using micro lens based optical integrators instead of a macro lens array. A simulation of the intensity distribution for 5 μm squares was performed to visualize the diffraction effects and to show the potential of 193 nm illumination. It is demonstrated that compared to the conventional homogenization optics the MO Exposure Optics further improves the illumination uniformity, calculated as 1.8% for MO Exposure Optics and 2.9% for the A-Optics. Moreover the improved optical setup allows a modification of the angular spectrum by using exchangeable illumination filter plates (IFP). Compared to the A-Optics the main improvement effect of MO Exposure Optics is detectable in the patterning of layouts containing critical dimension from 8 μm down to 2 μm.     

Full wafer microlens replication by UV imprint lithography

The fabrication of microlenses is of great interest for several applications in the field of optics like wafer level cameras, homogenization of light, and coupling of light into glass fibers. Especially for low-cost optical products, microlenses have to be fabricated with a high throughput at an adequate quality. One way to fulfil these requirements is the patterning of microlenses by UV imprint lithography (UV-IL). Within this work, microlenses were replicated into the UV curing material PAK-01 by step and stamp UV-IL on silicon substrates with a diameter of 150 mm. The resulting substrates were used as masters to cast PDMS templates. These PDMS templates can be used for high throughput full wafer UV-IL. Additionally, quartz substrates with a diameter of 100 mm were patterned which could be directly used as so called “optowafers”. Master and patterned microlenses were inspected by scanning electron microscopy and with a white light profilometer. The results clearly demonstrate the excellent quality of the replication process and the capability of UV-IL to pattern microlenses on full wafer level for high throughput applications.     

7.4 Gbit monolithically integrated GaAs/AlGaAs laser diode-laser driver structure

A molecular beam epitaxy (MBE) grown GaAs/AlGaAs multiquantum well laser, monolithically integrated with a laser driver was realised on 2 inch GaAs substrate wafers. In an optical data communication set up, performance up to data rates of 7.4 Gbit/s was demonstrated.<>     

LED spectral slicing for single-mode local loop applications

An approach towards a single-mode local loop is presented in which each customer is given a dedicated wavelength channel by taking different wavelength slices from identical LEDs. This is accomplished by means of wavelength division multiplexing (WDM) components. Results from a four-channel system operating at 2 Mbit/s over 2.2 km, together with a theoretical analysis of a ten-channel system, are presented     

Two beam surface fluctuation specular reflection spectroscopy

In surface fluctuation specular reflection spectroscopy (SFSRS) deflections of a specularly reflected laser beam are used to characterize thermally excited surface waves. Here we report on a new two beam version of SFSRS in which the deflections of two reflected laser beams from separate locations on a surface are correlated. We demonstrate that this new two beam SFSRS technique can be used to determine directly the power spectrum of height fluctuation of thermally excited surface waves over a large range of both frequencies and wavevectors. In addition, we show that the technique is well suited for materials ranging from simple liquids to complex liquids and soft solids, including turbid materials.     

Smart Scribbles for Sketch Segmentation

We present ‘Smart Scribbles’—a new scribble‐based interface for user‐guided segmentation of digital sketchy drawings. In contrast to previous approaches based on simple selection strategies, Smart Scribbles exploits richer geometric and temporal information, resulting in a more intuitive segmentation interface. We introduce a novel energy minimization formulation in which both geometric and temporal information from digital input devices is used to define stroke‐to‐stroke and scribble‐to‐stroke relationships. Although the minimization of this energy is, in general, an NP‐hard problem, we use a simple heuristic that leads to a good approximation and permits an interactive system able to produce accurate labellings even for cluttered sketchy drawings. We demonstrate the power of our technique in several practical scenarios such as sketch editing, as‐rigid‐as‐possible deformation and registration, and on‐the‐fly labelling based on pre‐classified guidelines.