Cryogenic connector for vacuum use Patent

Leakproof soft metal seal for use in very high vacuum systems operating at cryogenic temperature

Iodine monoxide in the Antarctic snowpack

Recent ground-based and space borne observations suggest the presence of significant amounts of iodine monoxide in the boundary layer of Antarctica, which are expected to have an impact on the ozone budget and might contribute to the formation of new airborne particles. So far, the source of these iodine radicals has been unknown. This paper presents long-term measurements of iodine monoxide at the German Antarctic research station Neumayer, which indicate that high IO concentrations in the order of 50 ppb are present in the snow interstitial air. The measurements have been performed using multi-axis differential optical absorption spectroscopy (MAX-DOAS). Using a coupled atmosphere snowpack radiative transfer model, the comparison of the signals observed from scattered skylight and from light reflected by the snowpack yields several ppb of iodine monoxide in the upper layers of the sunlit snowpack throughout the year. Snow pit samples from Neumayer Station contain up to 700 ng/l of total iodine, representing a sufficient reservoir for these extraordinarily high IO concentrations

Silent and Oral Reading Comprehension Abilities of Second Grade Students Completing the Second S.T.E.P. Program

This study focused on the silent and oral reading abilities of second grade students completing the Second S.T.E.P. Program. There were approximately seven second-grade students that participated. All 7 of the students are presently attending an elementary school located in western New York. The research questions concentrated on were: 1. Is there a statistically significant difference between the mean score of the pretest and the mean score of the posttest for unprompted memory, unprepared reading? 2. Is there a statistically significant difference between the mean score of the pretest and the mean score of the posttest for prompted memory, unprepared reading? 3. Is there a statistically significant difference between the mean score of the pretest and the mean score of the posttest for unprompted memory, prepared reading? 4. Is there a statistically significant difference between the mean score of the pretest and the mean score of the posttest for prompted memory, prepared reading? Each of the seven participants was administered in a one-on-one setting a pretest and a posttest version of the Bader Reading and Language Inventory in a 30-40 minute period. The pretest and the posttest each contained four sets of scores: unprompted memory (retelling), prompted memory (cued recall) after a unprepared (silent) reading and unprompted memory (retelling), prompted memory (cued recall) after a prepared (silent /oral) reading. The data were tallied and categorized into four sets of scores. Each set of scores was calculated utilizing a t-test of dependent means. The results of the t-test of dependent means indicated that there was no statistically significant difference between the mean pretest and mean posttest scores for all four sets of scores

Exploring barriers to 'Respondent driven sampling' in sex worker and drug-injecting sex worker populations in Eastern Europe

Respondent driven sampling (RDS) has been used in several counties to sample injecting drug users, sex workers (SWs) and men who have sex with men and as a means of collecting behavioural and biological health data. We report on the use of RDS in three separate studies conducted among SWs between 2004 and 2005 in the Russian Federation, Serbia, and Montenegro. Findings suggest that there are limitations associated with the use of RDS in SW populations in these regions. Findings highlight three main factors that merit further investigation as a means of assessing the feasibility and appropriateness of RDS in this high risk population: the network characteristics of SWs; the appropriate level of participant incentives; and lack of service contact. The highly controlled and hidden nature of SW organizations and weak SW social networks in the region can combine to undermine assumptions underpinning the feasibility of RDS approaches and potentially severely limit recruitment. We discuss the implications of these findings for recruitment and the use of monetary and non-monetary incentives in future RDS studies of SW populations in Eastern Europe

An Exact Solution For Modeling Photoacclimation of the Carbon-to-Chlorophyll Ratio in Phytoplankton

A widely-used theory of the photoacclimatory response in phytoplankton has, until now, been solved using a mathematical approximation that puts strong limitations on its applicability in natural conditions. We report an exact, analytic solution for the chlorophyll-to-carbon ratio as a function of the dimensionless irradiance (mixed layer irradiance normalized to the photoadaptation parameter for phytoplankton) that is applicable over the full range of irradiance occurring in natural conditions. Application of the exact solution for remote-sensing of phytoplankton carbon at large scales is illustrated using satellite-derived chlorophyll, surface irradiance data and mean photosynthesis-irradiance parameters for the season assigned to every pixel on the basis of ecological provinces. When the exact solution was compared with the approximate one at the global scale, for a particular month (May 2010), the results differed by at least 15% for about 70% of Northern Hemisphere pixels (analysis was performed during the northern hemisphere Spring bloom period) and by more than 50% for 24% of Northern Hemisphere pixels (approximate solution overestimates the carbon-to-chlorophyll ratio compared with the exact solution). Generally, the divergence between the two solutions increases with increasing available light, raising the question of the appropriate timescale for specifying the forcing irradiance in ecosystem models

Iterative maximum a posteriori (IMAP)-DOAS for retrieval of strongly absorbing trace gases: Model studies for CH_4 and CO_2 retrieval from near infrared spectra of SCIAMACHY onboard ENVISAT

In the past, differential optical absorption spectroscopy (DOAS) has mostly been employed for atmospheric trace gas retrieval in the UV/Vis spectral region. New spectrometers such as SCIAMACHY onboard ENVISAT also provide near infrared channels and thus allow for the detection of greenhouse gases like CH_4, CO_2, or N_2O. However, modifications of the classical DOAS algorithm are necessary to account for the idiosyncrasies of this spectral region, i.e. the temperature and pressure dependence of the high resolution absorption lines. Furthermore, understanding the sensitivity of the measurement of these high resolution, strong absorption lines by means of a non-ideal device, i.e. having finite spectral resolution, is of special importance. This applies not only in the NIR, but can also prove to be an issue for the UV/Vis spectral region

High spatial resolution measurements of NO₂ applying Topographic Target Light scattering-Differential Optical Absorption Spectroscopy (ToTaL-DOAS)

International audienceTomographic Target Light scattering ? Differential Optical Absorption Spectroscopy (ToTaL-DOAS), also called Target-DOAS, is a novel experimental procedure to retrieve trace gas concentrations present in the low atmosphere. Scattered sunlight (partially or totally) reflected from natural or artificial targets of similar albedo located at different distances is analyzed to retrieve the concentration of different trace gases like NO2, SO2 and others. We report high spatial resolution measurements of NO2 mixing ratios in the city of Montevideo (Uruguay) observing three buildings as targets with a Mini-DOAS instrument. Our instrument was 146 m apart from the first building, 196 m from the second and 286 m from the third one. All three buildings are located along a main Avenue. We obtain temporal variation of NO2 mixing ratios between 30 ppb and 65 ppb (±2 ppb). Our measurements demonstrate that ToTaL-DOAS measurements can be made over very short distances. In polluted air masses, the retrieved absorption signal was found to be strong enough to allow measurements over distances in the range of several ten meters, and achieve a spatial resolution of 50 m approximately