bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling a typical winter-time dust event over the Arabian Peninsula and the Red Sea
Authors: Kalenderski S. , Stenchikov G. , Zhao C.
Published: February 2013

Abstract. We used WRF-Chem, a regional meteorological model coupled with an aerosol-chemistry component, to simulate various aspects of the dust phenomena over the Arabian Peninsula and Red Sea during a typical winter-time dust event that occurred in January 2009. The model predicted that the total amount of emitted dust was 18.3 Tg for the entire dust outburst period and that the two maximum daily rates were ~2.4 Tg day−1 and ~1.5 Tg day−1, corresponding to two periods with the highest aerosol optical depth that were well captured by ground- and satellite-based observations. The model predicted that the dust plume was thick, extensive, and mixed in a deep boundary layer at an altitude of 3–4 km. Its spatial distribution was modeled to be consistent with typical spatial patterns of dust emissions. We utilized MODIS-Aqua and Solar Village AERONET measurements of the aerosol optical depth (AOD) to evaluate the radiative impact of aerosols. Our results clearly indicated that the presence of dust particles in the atmosphere caused a significant reduction in the amount of solar radiation reaching the surface during the dust event. We also found that dust aerosols have significant impact on the energy and nutrient balances of the Red Sea. Our results showed that the simulated cooling under the dust plume reached 100 W m−2, which could have profound effects on both the sea surface temperature and circulation. Further analysis of dust generation and its spatial and temporal variability is extremely important for future projections and for better understanding of the climate and ecological history of the Red Sea.
Position error in profiles retrieved from MIPAS observations with a 1-D algorithm
Authors: Carlotti M. , Arnone E. , Castelli E. , Dinelli B. M. , Papandrea E.
Published: February 2013

Abstract. The information load (IL) analysis, first introduced for the two-dimensional approach (Carlotti and Magnani, 2009), is applied to the inversion of MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) observations operated with a 1-dimensional (1-D) retrieval algorithm. The IL distribution of MIPAS spectra is shown to be often asymmetrical with respect to the tangent points of the observations and permits us to define the preferential latitude where the profiles retrieved with a 1-D algorithm should be geo-located. Therefore, defining the geo-location of the retrieved profile by means of the tangent points leads to a "position error". We assess the amplitude of the position error for some of the MIPAS main products and we show that the IL analysis can also be used as a tool for the selection of spectral intervals that, when analyzed, minimize the position error of the retrieved profile. When the temperature (T) profiles are used for the retrieval of volume mixing ratio (VMR) of atmospheric constituents, the T-position error (of the order of 1.5 degrees of latitude) induces a VMR error that is directly connected with the horizontal T gradients. Temperature profiles can be externally-provided or determined in a previous step of the retrieval process. In the first case, the IL analysis shows that a meaningful fraction (often exceeding 50%) of the VMR error deriving from the 1-D approximation is to be attributed to the mismatch between the position assigned to the external T profile and the positions where T is required by the analyzed observations. In the second case the retrieved T values suffer by an error of 1.5–2 K due to neglecting the horizontal variability of T; however the error induced on VMRs is of minor concern because of the generally small mismatch between the IL distribution of the observations analyzed to retrieve T and those analyzed to retrieve the VMR target. An estimate of the contribution of the T-position error to the error budget is provided for MIPAS main products. This study shows that the information load analysis can be successfully exploited in a 1-D context that makes the assumption of horizontal homogeneity of the analyzed portion of atmosphere. The analysis that we propose can be extended to the 1-D inversion of other limb-sounding experiments.
Comparison between MODIS and AIRS/AMSU satellite-derived surface skin temperatures
Authors: Lee Y.-R. , Yoo J.-M. , Jeong M.-J. , Won Y.-I. , Hearty T. , Shin D.-B.
Published: February 2013

Abstract. Surface skin temperatures of the Level 3 products of MODIS Collection 5 (C5) and AIRS/AMSU version 5 (V5) have been compared in terms of monthly anomaly trends and climatologies over the globe during the period from September 2002 to August 2011. The MODIS temperatures in the 50° N–50° S region tend to systematically be ~1.7 K colder over land and ~0.5 K warmer over ocean than the AIRS/AMSU temperatures. Over high latitude ocean the MODIS sea surface temperature (SST) values are ~5.5 K warmer than the AIRS/AMSU. The discrepancies between the annual averages of the two sensors are as much as ~12 K in the sea ice regions. Meanwhile, the MODIS ice surface temperature product (MYD29E1D) over the ocean is in better agreement with AIRS/AMSU temperatures, showing a root mean square error of 3.7–3.9 K. The disagreement between the two sensors results mainly from the differences in ice/snow emissivity between MODIS infrared and AMSU microwave, and also in their observational local times. Both MODIS and AIRS/AMSU show cooling rates from −0.05 ± 0.06 to −0.14 ± 0.07 K 9 yr−1 over the globe, but warming rates (0.02 ± 0.12 –0.15 ± 0.19 K 9 yr−1) in the high latitude regions.
Interannual variability of surface and bottom sediment transport on the Laptev Sea shelf during summer
Authors: Wegner C. , Bauch D. , Hölemann J. A. , Janout M. A. , Heim B. , Novikhin A. , Kassens H. , Timokhov L.
Published: February 2013

Abstract. Sediment transport dynamics were studied during ice-free conditions under different atmospheric circulation regimes on the Laptev Sea shelf (Siberian Arctic). To study the interannual variability of suspended particulate matter (SPM) dynamics and their coupling with the variability in surface river water distribution on the Laptev Sea shelf, detailed oceanographic, optical (turbidity and Ocean Color satellite data), and hydrochemical (nutrients, SPM, stable oxygen isotopes) process studies were carried out continuously during the summers of 2007 and 2008. Thus, for the first time SPM and nutrient variations on the Laptev Sea shelf under different atmospheric forcing and the implications for the turbidity and transparency of the water column can be presented. The data indicate a clear link between different surface distributions of riverine waters and the SPM transport dynamics within the entire water column. The summer of 2007 was dominated by shoreward winds and an eastward transport of riverine surface waters. The surface SPM concentration on the southeastern inner shelf was elevated, which led to decreased transmissivity and increased light absorption. Surface SPM concentrations in the central and northern Laptev Sea were comparatively low. However, the SPM transport and concentration within the bottom nepheloid layer increased considerably on the entire eastern shelf. The summer of 2008 was dominated by offshore winds and northward transport of the river plume. The surface SPM transport was enhanced and extended onto the mid-shelf, whereas the bottom SPM transport and concentration was diminished. This study suggests that the SPM concentration and transport, in both the surface and bottom nepheloid layers, are associated with the distribution of riverine surface waters which are linked to the atmospheric circulation patterns over the Laptev Sea and the adjacent Arctic Ocean during the open water season. A continuing trend toward shoreward winds, weaker stratification and higher SPM concentration throughout the water column might have severe consequences for the ecosystem on the Laptev Sea shelf.
Microbial bioavailability regulates organic matter preservation in marine sediments
Authors: Koho K. A. , Nierop K. G. J. , Moodley L. , Middelburg J. J. , Pozzato L. , Soetaert K. , van der Plicht J. , Reichart G-J.
Published: February 2013

Abstract. Burial of organic matter (OM) plays an important role in marine sediments, linking the short-term, biological carbon cycle with the long-term, geological subsurface cycle. It is well established that low-oxygen conditions promote organic carbon burial in marine sediments. However, the mechanism remains enigmatic. Here we report biochemical quality, microbial degradability, OM preservation and accumulation along an oxygen gradient in the Indian Ocean. Our results show that more OM, with biochemically higher quality, accumulates under low oxygen conditions. Nevertheless, microbial degradability does not correlate with the biochemical quality of OM. This decoupling of OM biochemical quality and microbial degradability, or bioavailability, violates the ruling paradigm that higher quality implies higher microbial processing. The inhibition of bacterial OM remineralisation may play an important role in the burial of organic matter in marine sediments and formation of oil source rocks.
Effect of ocean acidification on the fatty acid composition of a natural plankton community
Authors: Leu E. , Daase M. , Schulz K. G. , Stuhr A. , Riebesell U.
Published: February 2013

Abstract. The effect of ocean acidification on the fatty acid composition of a natural plankton community in the Arctic was studied in a large-scale mesocosm experiment, carried out in Kongsfjorden (Svalbard, Norway) at 79° N. Nine mesocosms of ~50 m3 each were exposed to 8 different pCO2 levels (from natural background conditions to ~1420 μatm), yielding pH values (on the total scale) from ~8.3 to 7.5. Inorganic nutrients were added on day 13. The phytoplankton development during this 30-day experiment passed three distinct phases: (1) prior to the addition of inorganic nutrients, (2) first bloom after nutrient addition, and (3) second bloom after nutrient addition. The fatty acid composition of the natural plankton community was analysed and showed, in general, high percentages of polyunsaturated fatty acids (PUFAs): 44–60% of total fatty acids. Positive correlations with pCO2 were found for most PUFAs during phases 2 and/or 3, with the exception of 20:5n3 (eicosapentaenoic acid, EPA), an important diatom marker. These correlations are probably linked to changes in taxonomic composition in response to pCO2. While diatoms (together with prasinophytes and haptophytes) increased during phase 3 mainly in the low and intermediate pCO2 treatments, dinoflagellates were favoured by high CO2 concentrations during the same time period. This is reflected in the development of group-specific fatty acid trophic markers. No indications were found for a generally detrimental effect of ocean acidification on the planktonic food quality in terms of essential fatty acids.
Seasonal signatures in SFG vibrational spectra of the sea surface nanolayer at Boknis Eck Time Series Station (SW Baltic Sea)
Authors: Laß K. , Bange H. W. , Friedrichs G.
Published: February 2013

Abstract. The very thin sea surface nanolayer on top of the sea surface microlayer, sometimes just one monomolecular layer thick, forms the interface between ocean and atmosphere. Due to the small dimension and tiny amount of substance, knowledge about the development of the layer in the course of the year is scarce. In this work, the sea surface nanolayer at Boknis Eck Time Series Station (BE), southwestern Baltic Sea, has been investigated over a period of three and a half years. Surface water samples were taken monthly by screen sampling and were analyzed in terms of organic content and composition by sum frequency generation spectroscopy, which is specifically sensitive to interfacial layers. A yearly periodicity has been observed with a pronounced abundance of sea surface nanolayer material (such as carbohydrate-rich material) during the summer months. On the basis of our results we conclude that the abundance of organic material in the nanolayer at Boknis Eck is not directly related to phytoplankton abundance. We suggest that indeed sloppy feeding of zooplankton together with photochemical and/or microbial processing of organic precursor compounds are responsible for the pronounced seasonality.
Turnover diversity drives large-scale biodiversity patterns in bathyal sediments of the Mediterranean Sea
Authors: Bianchelli S. , Gambi C. , Mea M. , Pusceddu A. , Danovaro R.
Published: February 2013

Abstract. Understanding biodiversity patterns and how they are driven at different spatial scales is a crucial issue in ecological studies. This is particularly evident for the deep sea, the largest biome of the biosphere, where information on the scales of spatial variation is very scant. Here, we investigated deep-sea nematodes species richness, turnover and functional diversity, and life strategies at different spatial scales (from local to macro-regional) to identify the factors that shape regional (γ) and macro-regional (ϵ) deep-sea diversity. This study was conducted in several deep-sea habitats (canyons, open slopes, deep-water corals, and bathyal plains) over > 2000 km across the whole Mediterranean basin, at a fixed depth of ca. 1000 m. Our results indicate that the patterns of local (α) diversity across the deep Mediterranean follow the gradients of the trophic conditions, which decrease from the Western to the Eastern basins. For all of the sites and habitats, the α-diversity is generally low. Conversely, the turnover diversity changes significantly among habitats (β-diversity) and between regions (δ-diversity), showing values of dissimilarity (based on species presence/absence) between 59% and 90% for β-diversity and between 81% and 89% for δ-diversity. This suggests that patterns and values of regional (γ) and macro-regional (ϵ) diversity in the deep Mediterranean Sea are related to turnover diversity among habitats and between regions (β- and δ-diversity), rather than to the local biodiversity (α-diversity). These results indicate that the differences in β-diversity and δ-diversity are even more important than those for the α-diversity for the understanding of the drivers of biodiversity in the deep Mediterranean Sea. These data also allow us to conclude that habitat heterogeneity (and type) and gradients in environmental conditions, by promoting a high turnover diversity across the deep Mediterranean Sea, are crucial players for the nematode diversity levels.
Can bioenergy cropping compensate high carbon emissions from large-scale deforestation of mid to high latitudes?
Authors: Dass P. , Müller C. , Brovkin V. , Cramer W.
Published: February 2013

Abstract. Numerous studies have concluded that deforestation of mid to high latitudes result in a global cooling. This is mainly because of the increased albedo of deforested land which dominates over other biogeophysical and biogeochemical mechanisms in the energy balance. This dominance however may be due to an underestimation of the biogeochemical response, as carbon emissions are typically at or below the lower end of estimates. Here, we use the dynamic global vegetation model LPJmL for a better estimate of the carbon cycle under such large-scale deforestation. These studies are purely academic to understand the role of vegetation in the energy balance and the earth system. They must not be mistaken as possible mitigation options, because of the devastating effects on pristine ecosystems. We show that even optimistic assumptions on the manageability of these areas and its utilization for bioenergy crops could not make up for the strong carbon losses in connection with the losses of vegetation carbon and the long-term decline of soil carbon stocks. We find that the global biophysical bioenergy potential is 78.9 ± 7.9 EJ yr−1 of primary energy at the end of the 21st century for the most plausible scenario. Due to avoided usage of fossil fuels over the time frame of this experiment, the cooling due to the biogeophysical feedback could be supplemented by an avoided warming of approximately 0.1 to 0.3 °C. However, the extensive deforestation simulated in this study causes an immediate emission of 182.3 ± 0.7 GtC followed by long term emissions. In the most plausible scenario, this carbon debt is not neutralized even if bioenergy production is assumed to be carbon-neutral other than for the land use emissions so that global temperatures would increase by ~0.2 to 0.6 °C by the end of the 21st century. The carbon dynamics in the high latitudes, especially with respect to permafrost dynamics and long-term carbon losses, require additional attention in the role for the Earth's carbon and energy budget.
Potential soil moisture products from the aquarius radiometer and scatterometer using an observing system simulation experiment
Authors: Luo Y. , Feng X. , Houser P. , Anantharaj V. , Fan X. , De Lannoy G. , Zhan X. , Dabbiru L.
Published: February 2013

Abstract. Using an observing system simulation experiment (OSSE), we investigate the potential soil moisture retrieval capability of the National Aeronautics and Space Administration (NASA) Aquarius radiometer (L-band 1.413 GHz) and scatterometer (L-band, 1.260 GHz). We estimate potential errors in soil moisture retrievals and identify the sources that could cause those errors. The OSSE system includes (i) a land surface model in the NASA Land Information System, (ii) a radiative transfer and backscatter model, (iii) a realistic orbital sampling model, and (iv) an inverse soil moisture retrieval model. We execute the OSSE over a 1000 × 2200 km2 region in the central United States, including the Red and Arkansas river basins. Spatial distributions of soil moisture retrieved from the radiometer and scatterometer are close to the synthetic truth. High root mean square errors (RMSEs) of radiometer retrievals are found over the heavily vegetated regions, while large RMSEs of scatterometer retrievals are scattered over the entire domain. The temporal variations of soil moisture are realistically captured over a sparely vegetated region with correlations 0.98 and 0.63, and RMSEs 1.28% and 8.23% vol/vol for radiometer and scatterometer, respectively. Over the densely vegetated region, soil moisture exhibits larger temporal variation than the truth, leading to correlation 0.70 and 0.67, respectively, and RMSEs 9.49% and 6.09% vol/vol respectively. The domain-averaged correlations and RMSEs suggest that radiometer is more accurate than scatterometer in retrieving soil moisture. The analysis also demonstrates that the accuracy of the retrieved soil moisture is affected by vegetation coverage and spatial aggregation.
A radiation hardened digital fluxgate magnetometer for space applications
Authors: Miles D. M. , Bennest J. R. , Mann I. R. , Millling D. K.
Published: February 2013

Abstract. Space-based measurements of the Earth's magnetic field are required to understand the plasma processes responsible for energizing particles in the Van Allen radiation belts and influencing space weather. This paper describes a prototype fluxgate magnetometer instrument developed for the proposed Canadian Space Agency (CSA) Outer Radiation Belt Injection, Transport, Acceleration and Loss Satellite (ORBITALS) mission and which has applications in other space and suborbital applications. The magnetometer is designed to survive and operate in the harsh environment of the Earth's radiation belts and measure low-frequency magnetic waves, the magnetic signatures of current systems, and the static background magnetic field. The new instrument offers improved science data compared to its predecessors through two key design changes: direct digitisation of the sensor and digital feedback combined with analog temperature compensation. These provide an increase in measurement bandwidth up to 450 Hz with the potential to extend to at least 1500 Hz. The instrument can resolve 8 pT on a 65 000 nT field with a magnetic noise of less than 10 pT per square–root Hz at 1 Hz. The prototype instrument was successfully tested and calibrated at the Natural Resources Canada Geomagnetics Laboratory showing that the mostly-digital design matches or exceeds its radiation-soft analog predecessor in sensitivity, noise, frequency range, and RMS accuracy.
Role of climate forecasts and initial conditions in developing streamflow and soil moisture forecasts in a rainfall–runoff regime
Authors: Sinha T. , Sankarasubramanian A.
Published: February 2013

Abstract. Skillful seasonal streamflow forecasts obtained from climate and land surface conditions could significantly improve water and energy management. Since climate forecasts are updated on a monthly basis, we evaluate the potential in developing operational monthly streamflow forecasts on a continuous basis throughout the year. Further, basins in the rainfall–runoff regime critically depend on the forecasted precipitation in the upcoming months as opposed to snowmelt regimes where initial hydrological conditions (IHC) play a critical role. The goal of this study is to quantify the role of updated monthly precipitation forecasts and IHC in forecasting 6-month lead monthly streamflow and soil moisture for a rainfall–runoff mechanism dominated basin – Apalachicola River at Chattahoochee, FL. The Variable Infiltration Capacity (VIC) land surface model is implemented with two forcings: (a) updated monthly precipitation forecasts from ECHAM4.5 Atmospheric General Circulation Model (AGCM) forced with sea surface temperature forecasts and (b) daily climatological ensembles. The difference in skill between the above two quantifies the improvements that could be attainable using the AGCM forecasts. Monthly retrospective streamflow forecasts are developed from 1981 to 2010 and streamflow forecasts estimated from the VIC model are also compared with those predicted by using the principal component regression (PCR) model. The mean square error (MSE) in predicting monthly streamflows, using the VIC model, are compared with the MSE of streamflow climatology under ENSO (El Niño Southern Oscilation) conditions as well as under normal years. Results indicate that VIC forecasts obtained using ECHAM4.5 are significantly better than VIC forecasts obtained using climatological ensembles and PCR models over 2–6 month lead time during winter and spring seasons in capturing streamflow variability and reduced mean square errors. However, at 1-month lead time, streamflow utilizing the climatological forcing scheme outperformed ECHAM4.5 based streamflow forecasts during winter and spring, indicating a dominant role of IHCs up to a 1-month lead time. During ENSO years, streamflow forecasts exhibit better skill even up to a six-month lead time. Comparisons of the seasonal soil moisture forecasts, developed using ECHAM4.5 forcings, with seasonal streamflows also show significant skill, up to a 6-month lead time, in the four seasons.
Modelling soil temperature and moisture and corresponding seasonality of photosynthesis and transpiration in a boreal spruce ecosystem
Authors: Wu S. H. , Jansson P.-E.
Published: February 2013

Abstract. Recovery of photosynthesis and transpiration is strongly restricted by low temperatures in air and/or soil during the transition period from winter to spring in boreal zones. The extent to which air temperature (Ta) and soil temperature (Ts) influence the seasonality of photosynthesis and transpiration of a boreal spruce ecosystem was investigated using a process-based ecosystem model (CoupModel) together with eddy covariance (EC) data from one eddy flux tower and nearby soil measurements at Knottåsen, Sweden. A Monte Carlo-based uncertainty method (GLUE) provided prior and posterior distributions of simulations representing a wide range of soil conditions and performance indicators. The simulated results showed sufficient flexibility to predict the measured cold and warm Ts in the moist and dry plots around the eddy flux tower. Moreover, the model presented a general ability to describe both biotic and abiotic processes for the Norway spruce stand. The dynamics of sensible heat fluxes were well described by the corresponding latent heat fluxes and net ecosystem exchange of CO2. The parameter ranges obtained are probably valid to represent regional characteristics of boreal conifer forests, but were not easy to constrain to a smaller range than that produced by the assumed prior distributions. Finally, neglecting the soil temperature response function resulted in fewer behavioural models and probably more compensatory errors in other response functions for regulating the seasonality of ecosystem fluxes.
Diagnostic Yield of Routine Duodenal Biopsies in Iron Deficiency Anemia for Celiac Disease Diagnosis
Authors: Chellat Houria , Salihoun Mouna , Kabbaj Nawal , Amrani Leila , Serraj Ilham , Chaoui Zakia , Nya M’hamed , Acherki Mohammed , Amrani Naïma
Published: February 2013

Background. Iron deficiency anemia (IDA) is a recognised feature of celiac disease (CD) in adults and can be its only presentation. Aim. To define the prevalence of CD in Moroccan adult patients with IDA of obscure origin and to determine the yield of small bowel biopsy performed during routine endoscopy. Methods. 437 patients with IDA of obscure origin were included. 4 endoscopic mucosal biopsies were taken from the second part of duodenum and 2 biopsies from antrum and fundus, respectively. Endoscopic aspect and severity of anemia were correlated with histological diagnoses using coefficient Kappa. Results. 29 out of 437 patients (6.63%) had CD. Endoscopic aspect was normal in 66%, a mosaic pattern of mucosa in 17%, and scalloping of the small bowel folds in 17%. 12 patients had Marsh III, 8 had Marsh II, 6 had Marsh I, and 3 had Marsh IV lesions. There was no correlation between degree of anemia, endoscopic aspect, and severity of duodenal lesions . Conclusion. Routine duodenal biopsy gives an additional 6.63% diagnostic benefit of CD and should be indicated in all patients with IDA. The finding of normal endoscopic appearance of mucosa should not preclude duodenal biopsies.
Unexpected High Prevalence of HPV 90 Infection in an Underserved Population: Is It Really a Low-Risk Genotype?
Authors: Quiroga-Garza Gabriela , Zhou Haijun , Mody Dina R. , Schwartz Mary R. , Ge Yimin
Published: February 2013

Context.—Human papillomavirus 90 (HPV 90) is a rarely reported genotype worldwide, with few data available to characterize its prevalence, distribution, and disease association.

Objective.—To investigate the prevalence, distribution, and disease association of HPV 90 infection in an underserved inner-city Latino population.

Design.—Residual SurePath specimens were collected from 808 women referred for abnormal Papanicolaou tests. DNA microarray against HPV subtypes determined HPV genotypes, followed by confirmatory DNA sequencing assays.

Results.—HPV 90 was detected in 32 women (4%) with an average age of 39 years (range, 23–42 years). Most women (31 of 32) had only HPV 90 infection, and one woman was coinfected with HPV 13. Two women had low-grade intraepithelial lesion and one woman had low-grade squamous intraepithelial lesion, cannot exclude high-grade squamous intraepithelial lesion; the rest of the women had negative concurrent cytology. Available concurrent biopsies in 2 of 3 instances with abnormal cytology confirmed HPV cytopathic effect, with no high-risk HPV detected by in situ hybridization.

Conclusions.—We demonstrated an unexpected, high infection rate of HPV 90 in an underserved population in the United States, with 9.4% having concurrent cytologic abnormalities. In the absence of other detectable HPV genotypes by DNA microarray, DNA sequencing, and in situ hybridization, we suspect HPV 90 may be a causative agent responsible for the concurrent cervical lesions. Because of potential shifts in HPV infection patterns in the postvaccine era, monitoring the emergence of previously underrecognized HPV genotypes is becoming increasingly important. To the best of our knowledge, this is the first study to characterize HPV 90 infection in an underserved, North American population.
Lens Coupler and Magnetic Field Terahertz Emission Enhancement in InSb and InAs under 1.55-µm Excitation
Authors: Nakajima Hidekazu , Que Christopher T. , Estacio Elmer S. , Yamamoto Kohji , Tani Masahiko
Published: February 2013

Terahertz (THz) emission from InSb and InAs utilizing an MgO lens coupler in conjunction with an applied magnetic field is reported. A THz peak amplitude enhancement of 74 times in InSb compared to 26 times in InAs was observed. The considerable enhancement in InSb is attributed to its large Hall angle, small THz divergence and reduced total internal reflection. A corresponding emission shift to lower THz frequencies in both samples was observed due to the spectral dependence of the MgO lens' collection efficiency. This enhancement configuration is easily applicable in the design of a compact THz time-domain spectroscopy system.
High Purity and Yield Separation of Semiconducting Single-Walled Carbon Nanotubes Dispersed in Aqueous Solutions with Density Gradient Ultracentrifugation Using Mixed Dispersants of Polysaccharides and Surfactants
Authors: Tsuchiya Koji , Uchida Katsumi , Kaminosono Yoshiya , Shimizu Kazushi , Ishii Tadahiro , Yajima Hirofumi
Published: February 2013

The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) prevents their potential applications in high-resolution field-effect transistors, nanoscale sensors, and conductive films. In the present study, we demonstrate the development of a new selective-separation procedure for collecting semiconducting single-walled carbon nanotubes (s-SWNTs) with a high purity from as-synthesized SWNTs individually dispersed with mixed dispersing agents consisting of carboxymethylcellulose (CMC) and sodium dodecyl sulfate (SDS) in water using density gradient ultracentrifugation (DGU). Ultraviolet–visible–near infrared (UV–vis–NIR) absorption, resonance Raman, and NIR photoluminescence spectroscopies revealed that the s-SWNTs were enriched to a purity of more than 97%, and that the recovery was approximately 40% through the DGU treatment. This separation strategy is expected to impact the application fields using s-SWNTs.
Effect of O3 and Aqueous Ammonia on Crystallization of MgO Thin Film Grown by Mist Chemical Vapor Deposition
Authors: Kawaharamura Toshiyuki , Mori Kazuharu , Orita Hiroyuki , Shirahata Takahiro , Fujita Shizuo , Hirao Takashi
Published: February 2013

Mist chemical vapor deposition (CVD) has been applied to fabricate MgO thin films under atmospheric pressure. In this work, to fabricate highly crystalline MgO thin films at low temperature, the effects of ozone gas (O3), aqueous ammonia (NH3), and a combination of O3 and NH3 on the crystallization temperature were studied by comparing samples grown under a standard condition of inactive gas such as argon (Ar). It was clarified that the crystallization temperature was decreased from 450 to 400 °C by the assistance of O3 and the crystallinity was improved by the addition of NH3. The growth of higher crystallinity MgO thin films at temperatures above 400 °C was possible by the combination of O3 and NH3, which caused stronger enhancement of the crystallization temperature and crystallinity. The causes of these effects were analyzed thermodynamically, and it was clarified that the results were due to the activated oxygen sources and the stability level of precursor materials in the solution.
Fast Imaging Ellipsometer Using a LiNbO3 Electrooptic Crystal
Authors: Jin Lianhua , Yagi Riyouma , Takizawa Kuniharu , Kondoh Eiichi
Published: February 2013

The LiNbO3 electrooptic crystal has been used as a phase modulator in polarimetry for fast single-point measurements. This paper aims to extend the application of the LiNbO3 electrooptic crystal to the two-dimensional polarimetric measurement and develop a fast imaging ellipsometer using the crystal. Ellipsometric imaging is made from intensity images measured at four-step phase modulation. The initial birefringence variance of the LiNbO3 electrooptic crystal across the view field is compensated by using a calibration sample. A complete image measurement is performed in 3.5 s. An Au-sputtered glass plate and a silicon wafer deposited with a patterned aluminum film are measured to examine the functionality of this ellipsometer. The measurement results show the feasibility of the application of this system to the qualitative measurements of samples.
Fabrication and Demonstration of 3-nm-Channel-Length Junctionless Field-Effect Transistors on Silicon-on-Insulator Substrates Using Anisotropic Wet Etching and Lateral Diffusion of Dopants
Authors: Migita Shinji , Morita Yukinori , Masahara Meishoku , Ota Hiroyuki
Published: February 2013

Junctionless field-effect transistors (JL-FETs) with a 3 nm channel length are fabricated on silicon-on-insulator (SOI) substrates using simple process techniques. The anisotropic etching of Si crystals by alkaline solution is utilized to form V-grooves and to define nanometer-scale channel structures. Ultrathin channels created on the SOI have a 3 nm channel length that is determined by the edge of V-grooves. Dopants are introduced by ion implantation at the source and drain regions and diffused into the channel region at a high temperature and by long-period annealing. V-groove JL-FETs thus fabricated show superior performances by scaling the thickness of the SOI channel toward 1 nm and less. Through the measurement of many V-groove JL-FETs and a simulation study, it is clarified that the management of channel thickness with atomic-scale precision is indispensable for sub-10 nm FETs.
Compound Semiconductor Tunneling Field-Effect Transistor Based on Ge/GaAs Heterojunction with Tunneling-Boost Layer for High-Performance Operation
Authors: Yoon Young Jun , Cho Seongjae , Seo Jae Hwa , Kang In Man , Park Byung-Gook , Lee Jung-Hee
Published: February 2013

In this work, a high-performance compound semiconductor tunneling field-effect transistor (TFET) based on germanium (Ge)/gallium arsenide (GaAs) heterojunction with a tunneling-boost layer is investigated. The tunneling-boost layer in the source-side channel alters the energy band-gap structure between the source and the channel, which affects current drivability considerably. It is shown that controlling the lengths of the boosting layer (thin n+ GaAs layer) and lightly doped p-type channel (p-GaAs) also has substantial effects on adjusting V
th without complications arising from shifting metal workfunction. Furthermore, we evaluate device performances such as on-state current (I
on), subthreshold swing (S), intrinsic delay time (τ), and cut-off frequency (f
T). The proposed TFET with an n-GaAs length of 12 nm showed an S of 27 mV/dec and approximately 3 times higher I
on than that of the device without a boosting layer. Moreover, it is confirmed from the extracted excellent radio-frequency (RF) parameters that the proposed device is suitable for RF applications.
A 3-mW/Gbps 1.8-V Operated Current-Reuse Low-Voltage Differential Signaling Driver Using Vertical Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Tanoi Satoru , Endoh Tetsuo
Published: February 2013

A low-voltage differential signaling (LVDS) driver with a new current reuse topology is proposed for low power-supply voltage (V
DD) operation. The proposed driver has a new current mirror with shared MOSFET and is designed using vertical MOSFETs. The new current mirror reduces the output degradation to less than half of the conventional. And the design with vertical MOSFETs reduces the voltage drop of the eight-stage cascode circuit to 77.6% of that with planar ones. Our current reuse driver achieves 3-mW/Gbps with 2.5-Gbps and 1.8-V V
DD operation in the simulation using 0.18-µm gate length MOSFET parameters. The achieved reduction of the power normalized by the output power at 1.8-V V
DD is larger than 30% of that for the conventional drivers.
93–133 GHz Band InP High-Electron-Mobility Transistor Amplifier with Gain-Enhanced Topology
Authors: Sato Masaru , Shiba Shoichi , Matsumura Hiroshi , Takahashi Tsuyoshi , Nakasha Yasuhiro , Suzuki Toshihide , Hara Naoki
Published: February 2013

In this study, we developed a new type of high-frequency amplifier topology using 75-nm-gate-length InP-based high-electron-mobility transistors (InP HEMTs). To enhance the gain for a wide frequency range, a common-source common-gate hybrid amplifier topology was proposed. A transformer-based balun placed at the input of the amplifier generates differential signals, which are fed to the gate and source terminals of the transistor. The amplified signal is outputted at the drain node. The simulation results show that the hybrid topology exhibits a higher gain from 90 to 140 GHz than that of the conventional common-source or common-gate amplifier. The two-stage amplifier fabricated using the topology exhibits a small signal gain of 12 dB and a 3-dB bandwidth of 40 GHz (93–133 GHz), which is the largest bandwidth and the second highest gain reported among those of published 120-GHz-band amplifiers. In addition, the measured noise figure was 5 dB from 90 to 100 GHz.
Fabrication and Characterization of Metal–Ferroelectric–Insulator–Semiconductor Capacitor Structure with Ferroelectric (Bi,Pr)(Fe,Mn)O3 Thin Films
Authors: Kawae Takeshi , Seto Yuichiro , Morimoto Akiharu
Published: February 2013

(Bi,Pr)(Fe,Mn)O3 (BPFM) thin films were deposited on SiO2/Si substrates by a chemical solution deposition method, resulting in the metal–ferroelectric–insulator–semiconductor (MFIS) capacitor structure. Polycrystalline BPFM films were grown on the substrate without impurity phases. Comparing with the capacitance vs voltage (C–V) curves of the MFIS capacitor structures with and without the BPFM self-barrier layer, the BPFM self-barrier layer suppress the formation of charge trap sites in the interface between the BPFM and SiO2 layers of the present structure, resulting in the prepared MFIS capacitor structure showing a clockwise C–V hysteresis behavior due to remnant polarization of the BPFM layer. The memory window width in the C–V curve was approximately 0.5 V for the bias voltage sweep from -20 to +20 V.
Effects of Trap Levels on Reverse Recovery Surge of Silicon Power Diode
Authors: Machida Satoru , Yamashita Yusuke , Misumi Tadashi , Sugiyama Takahide
Published: February 2013

In this paper, we report on the effects of trap energy levels on the reverse recovery surge, for the first time. The different current and temperature dependences of the reverse recovery surge with shallow and deep trap energy levels were measured. Results of simulations of current and temperature dependences of the reverse recovery surge with different trap energy levels were similar to measurement results. Through numerical and theoretical analyses based on the Shockley–Read–Hall (SRH) model, it was confirmed that variations in recombination rate due to different trap energy levels affect the current and temperature dependences of the reverse recovery surge. We found that in order to achieve a soft recovery in the design of silicon power diodes, the trap energy levels play a crucial role along with the carrier lifetime profile.
Improvement of Electrical Properties of Silicon Quantum Dot Superlattice Solar Cells with Diffusion Barrier Layers
Authors: Yamada Shigeru , Kurokawa Yasuyoshi , Miyajima Shinsuke , Konagai Makoto
Published: February 2013

We investigate the effects of a niobium-doped titanium dioxide (TiO2:Nb) diffusion barrier layer on the performance of silicon quantum dot superlattice (Si-QDSL) solar cells. The insertion of a 2-nm-thick TiO2:Nb layer significantly reduces phosphorus diffusion from a highly doped n-type layer into a Si-QDSL layer during thermal annealing at 900 °C. The phosphorous concentration in the Si-QDSL layer of the solar cell with the TiO2:Nb diffusion barrier layer was found to be less than 1018 cm-3, which is approximately two orders of magnitude lower than that of the solar cell without the diffusion barrier layer. The reduction in phosphorous concentration leads to the improvement of photo-generated carrier collection in the Si-QDSL layer. The short circuit current density of the solar cell with the diffusion barrier layer was dramatically improved to 1.6 mA/cm2 without the degradation of open circuit voltage and fill factor.
Self‐organization of elastic moduli in the rock above blind faults
Authors: Sleep Norman H.
Published: February 2013

Distributed anelastic deformation accommodates long‐term motion in the “lid” region above blind faults. The flowing sequence of cyclic processes may lead to self‐organization within lids composed of quartz‐rich clay‐bearing sedimentary rocks. Coseismic slip on the deep fault imposes strain and displacement on the lid. Sufficient strain brings the lid to frictional failure, producing distributed cracks. Cracked lid becomes increasing elastically compliant over many seismic cycles. The lid tends to evolve so that coseismic displacement barely causes frictional failure; hence, only a few new cracks open within the lid. However, this process cannot increase crack porosity and decrease the shear modulus below values where the material would readily compact under lithostatic pressure. Accumulating sedimentary rocks provide a convenient proxy for this limit. Numerical modeling indicates that the (geodetic) coseismic displacement above a compliant lid is much of the total geodetic displacement that would be observed over a full cycle. Stresses within the lid relax by ductile creep at nearly constant strain with only modest geodetic displacement >100 year after the earthquake for a 1000 year cycle.
Lichtstrahlen – Realität oder Fiktion?: Ein experimenteller Beitrag mit einfachen Demonstrationen
Authors: Koppelmann G.
Published: February 2013

In zahlreichen Physiklehrer‐Fortbildungskursen hat G. Koppelmann zusammen mit seinen Mitarbeitern in den letzten zwölf Jahren versucht, Ergebnisse und Anwendungen auf verschiedenen Gebieten der modernen Physik zu elementarisieren und in einfachen Unterrichtsexperimenten deutlich und anschaulich zu machen. Zu den halb‐ bis eintägigen Kompaktkursen gehören jeweils außer experimentellen Vorträgen auch Praktika. Als Kursmaterial erhalten die Teilnehmer neben ausführlichen Skripten einige sonst nicht oder nur schwer erhältliche einfache experimentelle Hilfsmittel und Muster, die meistens speziell hierfür entwickelt oder auch als Industriespenden eingeworben wurden. Sie sollen es den Physiklehrern ermöglichen, die Versuche mit Schulmitteln im eigenen Unterricht vorzuführen und moderne Anwendungen konkret zu zeigen.
Computersimulationen zur Polymerdynamik
Authors: Kremer K.
Published: February 2013

An zwei konzeptionell einfachen Beispielen, dem einzelnen Polymer im Lösungsmittel und einer Schmelze von identischen Polymeren, wird erläutert, welche Rolle Computersimulationen in der modernen Polymerphysik spielen können. Für die Kette im Lösungsmittel konnte das Zimm‐Modell mikroskopisch bestätigt werden, während für Schmelzen das Reptationsmodell von de Gennes und Edwards eine sehr gute Beschreibung der Dynamik liefert.
Das goldene Zeitalter der deutschen Physik und die Emotionen der Physiker: Festvortrag zum 150‐jährigen Jubiläum der DPG am 22. März 1995 in der Berliner Oper
Authors: Hermann A.
Published: February 2013

Die von den Laien oft als “kalte Verstandesmenschen” eingeschätzten Physiker erweisen sich bei näherer Betrachtung als hochemotional. Tatsächlich erfordert der Prozeß der geistigen Schöpfung, der zu einer neuen Theorie oder einem neuen Experiment führt, die Beteiligung des unbewußten Bereiches der Psyche. Außerordentlich emotional haben sich die Gelehrten insbesondere während des vielbesprochenen Umsturzes im Weltbild der Physik verhalten. So empfand, ein Beispiel von vielen, Erwin Schrödinger die Göttinger Matrizenmechanik als “abstoßend” und “unerträglich” und wollte mit seiner Wellenmechanik zurück zur klassischen Physik. Auch Wilhelm Wien fühlte sich erleichtert, daß nun ‐ wie er meinte ‐ die “Quantentheorie doch wieder in die klassische einmünden” würde und die jungen Physiker “nicht mehr in dem Sumpf von ganzen und halben Quantendiskontinuitäten herumplätschern konnten”. Als Werner Heisenberg nach einem Vortrag Schrödingers in München seine Kritik vorbrachte, warf ihn Wilhelm Wien beinahe aus dem Hörsaal: “Junger Mann, Sie müssen erst noch Physik lernen.”
Neue Wege gehen, um unbekanntes Gebiet zu erschließen
Authors: Maier‐Leibnitz H.
Published: February 2013

In seinem Festvortrag anläßlich der Verleihung der Stern‐Gerlach‐Medaille gab Professor Heinz Maier‐Leibnitz einen sehr persönlich gehaltenen Einblick in die vielen grundlegenden Beiträge zur Neutronenmeßtechnik, die von ihm und seinen Mitarbeitern an der TU München ausgegangen sind. Als wesentlich für den Erfolg bezeichnet er die Prägung durch seine Lehrer, insbesondere James Franck und Walther Bothe. Für den „Nestor”︁ der Neutronenphysik in Deutschland, dessen Namen wie kaum ein zweiter für die Entdeckung und Entwicklung von Neuem steht, bleibt eine Frage aber unbeantwortet: Wie kommt man auf einfaches Neues? (Red.)
Mehr Innovation durch Doppelfunktion: Professur und Firmentätigkeit
Authors: Helfrich W.
Published: February 2013

In Krisenzeiten, aber nicht nur dann, ist Denken in Alternativen willkommen. Vor dem Hintergrund des eigenen beruflichen Werdegangs kommt Professor Helfrich zu dem Schluß, daß die Institutionalisierung von Doppelfunktionen — Hochschullehrer und gleichzeitig Industrieforscher — ein Weg wäre, die Innovationsschwäche in Deutschland zu überwinden. (Red.)
Magnetische Resonanz an einzelnen Molekülen (II): Kohärente Experimente an einzelnen Elektronenspins
Authors: Wrachtrup J.
Published: February 2013

Die verschiedensten klassischen Methoden der Spektroskopie erleben derzeit einen rasanten Wandel hin zu mikroskopischen bzw. nanoskopischen Untersuchungen. Durch die optische Detektion von Elektronenspinresonanz (ESR) läßt sich dieser allgemeine Trend auch auf die magnetische Resonanz übertragen — ein einzelner Elektronenspin und seine Wechselwirkung mit der Umgebung werden sichtbar.
Gravitationsphysik an deutschen Universitäten ohne Zukunft?
Authors: Hehl F. W. , Kiefer C. , Lämmerzahl U. C.
Published: February 2013

Es ist zu befürchten, daß in fünf Jahren nur noch an einer einzigen deutschen Universität die Allgemeine Relativitätstheorie von hauptamtlichen Professoren in Forschung und Lehre vertreten wird. Diesem Abbau der ohnehin schon stark unter‐repräsentierten Gravitationsphysik sollte mit allen Mitteln entgegengewirkt werden.
Tagungsnachlese Regensburg — Arbeitskreis Festkörperphysik: „Anwendung, Anwendung über alles?”︁
Authors: Wandelt K.
Published: February 2013

Die Fachsitzungen der vertretenen Fachverbände mit Vortrags‐ und Posterbeiträgen fanden jeweils im Anschluß an die morgendlichen Plenarveranstaltungen statt. Die folgenden Kurzberichte der Vorsitzenden (Name jeweils am Ende in Klammern) der einzelnen Fachverbände heben besonders die jeweiligen Highlights hervor, die zumeist durch Haupt‐ bzw. Fachvorträge markiert wurden und Serien von Kurzvorträgen zur entsprechenden Thematik einleiteten. Unübersehbar geht aus diesen Berichten ein deutlicher Trend zur Betonung der Anwendungsrelevanz (gar als Rechtfertigung?) der vorgestellten Forschungsarbeiten hervor