Radiation tolerance of vertical junction solar cells

Extensive radiation testing of vertical junction (VJ) solar cells demonstrated a radiation tolerance better than both planar silicon cells and at least one type of (AlGa)As-GaAs cell. Due to tradeoffs between short circuit current and open circuit voltage, the end of life (10 to the 16th power 1 MeV electrons/sq cm) maximum power point is nearly independent of bulk resistivity between 2 and 10 ohm cm, increases slightly with increasing wafer thickness between 3 and 11 mils, and increases slightly with increasing groove depth between 1 and 3 mils

RURAL GROWTH IN U.S. HEARTLAND

This study identifies factors that explain growth in rural areas using data from 618 counties in the U.S. rural heartland. We evaluate many of the growth hypotheses in the context of sectoral employment growth for counties in Iowa, Minnesota, Missouri, Kansas, Nebraska, South Dakota and North Dakota. Separate estimates for rural and urban counties provide insight into factors that are important in explaining employment growth. The results support the importance of human capital as a factor contributing to sectoral employment growth and show that increased concentration and specialization of employment within a county lead to slower growth in the rural heartland counties.Community/Rural/Urban Development,

Coplanar back contacts for thin silicon solar cells

The type of coplanar back contact solar cell described was constructed with interdigitated n(+) and p(+) type regions on the back of the cell, such that both contacts are made on the back with no metallization grid on the front. This cell construction has several potential advantages over conventional cells for space use namely, convenience of interconnects, lower operating temperatures and higher efficiency due to the elimination of grid shadowing. However, the processing is more complex, and the cell is inherently more radiation sensitive. The latter problem can be reduced substantially by making the cells very thin (approximately 50 micrometers). Two types of interdigitated back contact cells are possible, the types being dependent on the character of the front surface. The front surface field cell has a front surface region that is of the same conductivity type as the bulk but is more heavily doped. This creates an electric field at the surface which repels the minority carriers. The tandem junction cell has a front surface region of a conductivity type that is opposite to that of the bulk. The junction thus created floats to open circuit voltage on illumination and injects carriers into the bulk which then can be collected at the rear junction. For space use, the front surface field cell is potentially more radiation resistant than the tandem junction cell because the flow of minority carriers (electrons) into the bulk will be less sensitive to the production of recombination centers, particularly in the space charge region at the front surface

Specific arrangements of species dominance can be more influential than evenness in maintaining ecosystem process and function

The ecological consequences of species loss are widely studied, but represent an end point of environmental forcing that is not always realised. Changes in species evenness and the rank order of dominant species are more widespread responses to directional forcing. However, despite the repercussions for ecosystem functioning such changes have received little attention. Here, we experimentally assess how the rearrangement of species dominance structure within specific levels of evenness, rather than changes in species richness and composition, affect invertebrate particle reworking and burrow ventilation behaviour - important moderators of microbial-mediated remineralisation processes in benthic environments - and associated levels of sediment nutrient release. We find that the most dominant species exert a disproportionate influence on functioning at low levels of evenness, but that changes in biomass distribution and a change in emphasis in species-environmental interactions become more important in governing system functionality as evenness increases. Our study highlights the need to consider the functional significance of alterations to community attributes, rather than to solely focus on the attainment of particular levels of diversity when safeguarding biodiversity and ecosystems that provide essential services to society

Translational sensitivity of the Escherichia coli genome to fluctuating tRNA availability

The synthesis of protein from messenger RNA during translation is a highly dynamic process that plays a key role in controlling the efficiency and fidelity of genome-wide protein expression. The availability of aminoacylated transfer RNA (tRNA) is a major factor influencing the speed of ribosomal movement, which depending on codon choices, varies considerably along a transcript. Furthermore, it has been shown experimentally that tRNA availability can vary signifi-cantly under different growth and stress conditions, offering the cell a way to adapt translational dynamics across the genome. Existing models of translation have neglected fluctuations of tRNA pools, instead assuming fixed tRNA availabilities over time. This has lead to an incomplete under-standing of this process. Here, we show for the entire Escherichia coli genome how and to what extent translational speed profiles, which capture local aspects of translational elongation, respond to measured shifts in tRNA availability. We find that translational profiles across the genome are affected to differing degrees, with genes that are essential or related to fundamental processes such as transla-tion, being more robust than those linked to regula-tion. Furthermore, we reveal how fluctuating tRNA availability influences profiles of specific sequences known to play a significant role in translational control of gene expression

Does the Analysis of Separate Bands of Echo Intensity Strengthen the Relationship to Muscle Function?

Ultrasound echo intensity (EI) has been proposed as a method of assessing muscle quality through the use of non-invasive imaging. Traditionally, EI is assessed as the mean pixel brightness that ranges from 0-255 within an area of interest. However, it may be reasonable to consider that additional portions of the ultrasound EI signal (i.e., bands of signal) may provide novel insight to muscle function. The determination of which band of signal may be more related to a given functional outcome may increase the sensitivity of EI. Thus far, there is no research analyzing the association between EI bands and fatigue. PURPOSE: The purpose of this study was to compare relationships between mean echo intensity and unique bands of ultrasound signal of the vastus lateralis with metrics of whole muscle performance in healthy adults. METHODS: Twenty-four participants (mean ± age = 22 ± 3.9 yrs; BMI = 25.7 ± 3.4 kg/m2), completed two visits to the laboratory. On the first visit, subjects completed Brightness mode (B-mode) ultrasound imaging and were familiarized with the fatigue assessment. Between two and seven days later, subjects returned for the testing visit. B-mode ultrasound was used to image the vastus lateralis (VL) at 50% muscle length. The VL cross-sectional area was traced using the polygon tool. As much of the muscle was selected without selecting any of the surrounding fascia. Each pixel is assigned a brightness value from 0-255 based on gray scale; 0 representing true black and 255 is pure white. Mean EI was quantified from within the selected portion of the image. Echo intensity bands were calculated in pixel value intervals of 0-49, 50-99, 100-149, 150-199, 200-255. The percentage of pixels per band compared to the total number of pixels in each image was assessed by: (number of pixels in each band/ total number of pixels in the selected portion of the image)*100. For the fatigue assessment, participants completed 100 repeated, maximal, isokinetic muscle actions (120°/sec). Isokinetic peak torque was analyzed offline using custom written software by selecting individual torque peaks from each muscle action. Initial and final isokinetic peak torque were calculated by averaging the highest 3 of the first 5 and the highest 3 of the last 5 contractions. Isokinetic peak torque percent decline (%Decline) was calculated by: %Decline = (initial – PT – final - PT)/initial - PT. Pearson’s correlation coefficient (r) was used to assess the relationship between each EI band and %Decline as well as mean EI and %Decline. The Stieger’s Z procedure was used to compare the correlation coefficients between mean EI and each EI band. RESULTS: There were no significant correlation between mean EI and %Decline (r=0.03, p=0.88) or any of the EI bands and %Decline (r=-0.07-0.3, p=0.16-0.89). Additionally, there were no significant relationships between the mean EI and any of the EI bands (z=0.001-0.88, p=0.38-0.99). CONCLUSION: The findings suggest that unique bands of ultrasound signal do not offer different relationships compared to overall mean EI when assessing fatigue from repetitive isokinetic muscle actions

Reliability of Differing Muscle Size and Quality Analysis Techniques

Brightness-mode (B-mode) ultrasonography is a popular tool to examine anatomical cross-sectional area (ACSA) and echo intensity (EI). Muscle ACSA and EI provide valuable insight into muscle function due to their unique mechanisms which influence performance. Manually analyzing ultrasound images potentially increases variability which may increase error, thus decreasing the reliability of manual image analysis. Recently an automated program was created to improve reliability and reduce the time of ultrasound image analysis. PURPOSE: The purpose of this study was to investigate the reliability of manual compared to automatic ultrasound analyses of muscle cross-sectional area and echo intensity. METHODS: Twenty-two participants (mean ± SD age = 24 ± 4 yrs; BMI = 24.19 ± 3.26 kg/m2) volunteered for this study. The participants completed one visit to the laboratory consisting of two data collection trials separated by 10 minutes. Ultrasound scans were taken with a B-mode ultrasound imaging device and image settings were held constant (i.e., depth = 6 cm, frequency = 12 MHz, gain = 52 dB). For each trial, participants remained supine while ACSA scans of the vastus lateralis (VL) were taken at 50% the length of the proximal to distal musculo-tendon junctions. The ACSA of the VL was manually analyzed by an experienced technician with ImageJ using the polygon tool and tracing the area of interest. Echo intensity was quantified as the mean pixel brightness of the traced portion of the image. Images were automatically analyzed with the Deep Anatomical Cross-Sectional Area (DeepACSA) program which is an algorithm that is designed to automatically trace the area of interest of an ultrasound image. Test-retest reliability statistics (i.e., intraclass correlation coefficient [ICC] model 2,1, standard error of measure expressed as a percentage of the mean [SEM%], and the minimal differences [MD] values needed to be considered real) were calculated for trials 1 and 2. One-way repeated measures analysis of variance determined differences in trial 1 compared to trial 2. RESULTS: Manual analyses of ACSA (ICC2,1 = 0.98, SEM (%) = 3.39%, MD = 2.09 cm2, p = 0.046) were more reliable than automatic analyses (ICC2,1 = 0.87, SEM (%) = 12.33%, MD = 7.77 cm2, p = 0.216). Manual analyses of EI (ICC2,1 = 0.73, SEM (%) = 6.44%, MD = 10.83 cm2, p = 0.514) had similar reliability to the automatic analyses (ICC2,1 = 0.88, SEM (%) = 3.60%, MD = 6.30 cm2, p = 0.003). CONCLUSION: These results suggest that this automated analysis program may be less reliable compared to the manual analysis of muscle ACSA of the VL. Conversely, DeepACSA displayed similar reliability for EI of the VL when compared to the manual analysis

Translation error clusters induced by aminoglycoside antibiotics

Aminoglycoside antibiotics target the ribosome and induce mistranslation, yet which translation errors induce bacterial cell death is unclear. The analysis of cellular proteins by quantitative mass spectrometry shows that bactericidal aminoglycosides induce not only single translation errors, but also clusters of errors in full-length proteins in vivo with as many as four amino acid substitutions in a row. The downstream errors in a cluster are up to 10,000-fold more frequent than the first error and independent of the intracellular aminoglycoside concentration. The prevalence, length, and composition of error clusters depends not only on the misreading propensity of a given aminoglycoside, but also on its ability to inhibit ribosome translocation along the mRNA. Error clusters constitute a distinct class of misreading events in vivo that may provide the predominant source of proteotoxic stress at low aminoglycoside concentration, which is particularly important for the autocatalytic uptake of the drugs

Test-Retest Reliability of Automatic and Manual Image Analyses of Muscle Size

Brightness-mode (B-mode) ultrasound is a non-invasive imaging modality that has risen in popularity. In research settings, B-mode ultrasound is often used to assess skeletal muscle size via the quantification of the anatomical cross-sectional area (ACSA). Typically, these images are analyzed by an experienced investigator using open-source software, though it is a time-consuming process that may introduce implicit bias into the analysis. Recently, a novel, automatic ultrasound image analysis tool has been developed which may reduce bias and increase the reliability of ultrasound ACSA image analysis. PURPOSE: The purpose of the project was to compare the test-retest reliability of manual and automatic ACSA quantification techniques. METHODS: Nine participants (mean ± SD: age = 25 ± 3 years; BMI = 23.96 ± 2.62 kg/m2) completed one laboratory visit where each participant had non-invasive ultrasound imaging performed on their rectus femoris (i.e., RF) for two data collection trials separated by 10 minutes. For each participant, ultrasound image settings were held constant (i = 6 cm, frequency = 10 MHz, gain = 52 dB). All images were manually analyzed by an experienced technician using an open-source image analysis tool. The investigator would carefully select only the surrounding muscle fascia of the RF. Automatic analyses were performed using DeepACSA, a deep learning approach for the assessment of ACSA. Both manual and automatic analyses were conducted on all images. Analysis of variance (ANOVA) was conducted to compare differences between trials and test-retest reliability (i.e., intraclass correlation coefficients [ICC] model 2,1, standard error of measure expressed as a percentage of the mean [SEM%], and the minimal differences [MD] values needed to be considered real) were calculated from the ANOVA output. RESULTS: The manual analyses of ACSA (p = 0.20, ICC2,1 = 0.84, SEM (%) = 11.67%, MD = 1.75 cm2) were more reliable than the DeepACSA analyses (p = 0.13, ICC2,1 = 0.47, SEM (%) = 30.28%, MD = 4.70 cm2). CONCLUSION: The results of the present investigation suggest that the DeepACSA approach may be less reliable compared to the manual quantification of RF muscle size. Future studies should investigate using a larger sample size and additional muscle groups

Attention and the motion after effect

We measured the effects of attentional distraction on the time course and asymptote of motion adaptation strength, using visual search performance (percent correct and reaction time). In the first two experiments, participantsadapted to a spatial array of moving Gaborpatches, either all vertically oriented (Experiment 1) or randomly oriented (Experiment 2). On each trial the adaptingarray was followed by a test array in which all of the test patchesexcept one were identical in orientation and movement direction to their retinotopically corresponding adaptors, but thetarget moved in the opposite direction to its adaptor. Participantswere required to identify the location of the changed targetwith a mouse click. The ability to do so increased with the number of adapting trials. Neither search speed nor accuracy was affected by an attentionallydemanding conjunction task at the fixation point during adaptation, suggesting low-level (pre-attentive) sites in the visual pathway for the adaptation. In Experiment 3 the same participants were required to identify the one element in the test array that was slowly moving. Reaction times in this case were elevated following adaptation, but once again there was nosignificant effect of the distracting task upon performance.In Experiment 4 participants were required to make eye movements, so that retinotopically corresponding adaptors could be distinguished from spatiotopically corresponding adaptors.Performance in Experiments 1 and 2 correlated positively with reaction times in Experiment 3, suggesting a general trait for adaptation strength