Estimation of reactive inorganic iodine fluxes in the Indian and Southern Ocean marine boundary layer

Iodine chemistry has noteworthy impacts on the oxidising capacity of the marine boundary layer (MBL) through the depletion of ozone (O3) and changes to HOx (OH=HO2) and NOx (NO=NO2) ratios. Hitherto, studies have shown that the reaction of atmospheric O3 with surface seawater iodide (I-) contributes to the flux of iodine species into the MBL mainly as hypoiodous acid (HOI) and molecular iodine (I2). Here, we present the first concomitant observations of iodine oxide (IO), O3 in the gas phase, and sea surface iodide concentrations. The results from three field campaigns in the Indian Ocean and the Southern Ocean during 2015 2017 are used to compute reactive iodine fluxes in the MBL. Observations of atmospheric IO by multi-axis differential optical absorption spectroscopy (MAX-DOAS) show active iodine chemistry in this environment, with IO values up to 1 pptv (parts per trillion by volume) below latitudes of 40° S. In order to compute the sea-to-air iodine flux supporting this chemistry, we compare previously established global sea surface iodide parameterisations with new regionspecific parameterisations based on the new iodide observations. This study shows that regional changes in salinity and sea surface temperature play a role in surface seawater iodide estimation. Sea air fluxes of HOI and I2, calculated from the atmospheric ozone and seawater iodide concentrations (observed and predicted), failed to adequately explain the detected IO in this region. This discrepancy highlights the need to measure direct fluxes of inorganic and organic iodine species in the marine environment. Amongst other potential drivers of reactive iodine chemistry investigated, chlorophyll a showed a significant correlation with atmospheric IO (R D 0:7 above the 99 % significance level) to the north of the polar front. This correlation might be indicative of a biogenic control on iodine sources in this region

Optimization of LPCVD-SiNx Membranes for Micro-hotplate/Nano-reactors

Micro-hotplate and Micro-hotplate integrated Nano-reactors are a revolution for in-situ observations in Transmission Electron Microscopy (TEM) imaging. They currently operate at about 400oC without any problems. The SiNx membranes of micro-hotplate and Nano-reactors have integrated micro-heater along with electron transparent windows. The major problem is the shift in 'z' direction of the membranes as a function of pressure and temperature. This creates a change in focus during in-situ TEM imaging affecting the image quality. Net compressive forces can be a reason for bending of membranes, as far as temperature is concerned. Thus, introduction of residual tensile stress was considered to solve this problem. Simple COMSOL simulations were made using plate models to verify the effect of residual tensile stress in membranes as a function of temperature and pressure individually, as well as a combination of both. It was concluded that residual tensile stress does reduce thermal buckling. It also reduces the bulging due to pressure but bulging as a function of pressure can't be made zero. It also concludes thermal buckling is more dominant at lower pressure and pressure bulge is more dominant at higher pressure. Different residual stress LPCVD SiNx films were deposited and material properties like Young's modulus, refractive index and density were characterized. A saturation to the deposition and residual tensile stress was found as a function of gas-ratio. Surface morphology and IR spectra were also determined using AFM and FTIR respectively. All the characterization done proves the change in material composition with fabrication parameters. The introduction of high residual stress questions the reliability of the membrane and hence, there was a need to check if high tensile residual stress doesn't break the membranes. Thus, a new device for wafer level pressure testing of membranes was designed and fabricated. The pressure bulge test was done and reflections were recorded for various pressure and stress levels. The membranes were found reliable up to a pressure of 1.5 bar. New generation of micro-hotplates were fabricated using this concept and an increment 400oC in the operating temperature of micro-hotplates and nano-reactors, without any-shift in 'z' direction due to temperature, was achieved.Electrical Engineerin

Network Subsystems Reloaded: A High-Performance, Defensible Network Subsystem

Traditionally, operating systems have used monolithic network stack implementations: implementations where the whole network stack executes in the kernel or (in microkernels) in a single, trusted, user level server

Network Subsystems Reloaded: A High-Performance, Defensible Network Subsystem

Traditionally, operating systems have used monolithic network stack implementations: implementations where the whole network stack executes in the kernel or (in microkernels) in a single, trusted, user level server. Code maintenance issues, ease of debugging, need for simultaneous existence of multiple protocols, and security benefit have argued for removing the networking implementation from kernel and dividing it into multiple user level protection domains. Previous attempts to do so have failed to deliver adequate performance. Given the advances made in both hardware (CPU, Memory, NIC) and micro-kernel design over the last decade, it is now appropriate to re-evaluate how these re-factored implementations perform, and to examine the reasons for earlier failures in greater detail. Building on the primitives of the EROS microkernel, we have implemented two network subsystems: one a conventional, user mode, monolithic design and the other a domain-factored user level networking stack that restructures the network subsystem into several protection domains. We show that the restructuring maintains performance very close to that of the monolithic design, and that both designs compare favorably to a conventional in-kernel implementation. We discuss the issues faced in engineering the domain-factored implementation to achieve high performance, and present the quantitative evaluation of the resulting network subsystems.

Solving stochastic programming problems via Kalman filter and affine scaling

http://deepblue.lib.umich.edu/bitstream/2027.42/7184/5/bap4042.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/7184/4/bap4042.0001.001.tx