Fast Data Sorting with Modified Principal Component Analysis to Distinguish Unique Single Molecular Break Junction Trajectories.

A simple and fast analysis method to sort large data sets into groups with shared distinguishing characteristics is described and applied to single molecular break junction conductance versus electrode displacement data. The method, based on principal component analysis, successfully sorts data sets based on the projection of the data onto the first or second principal component of the correlation matrix without the need to assert any specific hypothesis about the expected features within the data. This is an improvement on the current correlation matrix analysis approach because it sorts data automatically, making it more objective and less time consuming, and our method is applicable to a wide range of multivariate data sets. Here the method is demonstrated on two systems. First, it is demonstrated on mixtures of two molecules with identical anchor groups and similar lengths, but either a π (high conductance) or a σ (low conductance) bridge. The mixed data are automatically sorted into two groups containing one molecule or the other. Second, it is demonstrated on break junction data measured with the π bridged molecule alone. Again, the method distinguishes between two groups. These groups are tentatively assigned to different geometries of the molecule in the junction.

Isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners.

The true differences between barefoot and shod running are difficult to directly compare because of the concomitant change to a mid/forefoot footfall pattern that typically occurs during barefoot running. The purpose of this study was to compare isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners running shod (SHOD), barefoot (BF), and barefoot on a foam surface (BF+FOAM). Ten habitually shod mid/forefoot runners were recruited (male = 8, female = 2). Repeated measures ANOVA (α = 0.05) revealed differences between conditions for only vertical peak active force, contact time, negative and total ankle joint work, and peak dorsiflexion angle. Post hoc tests revealed that BF+FOAM resulted in smaller vertical active peak magnitude and instantaneous vertical loading rate than SHOD. SHOD resulted in lower total ankle joint work than BF and BF+FOAM. BF+FOAM resulted in lower negative ankle joint work than either BF or SHOD. Contact time was shorter with BF than BF+FOAM or SHOD. Peak dorsiflexion angle was smaller in SHOD than BF. No other differences in sagittal joint kinematics, kinetics, or ground reaction forces were observed. These overall similarities in running mechanics between SHOD and BF+FOAM question the effects of footwear structure on habituated mid/forefoot running described previously.

Gap States in Methylammonium Lead Halides: The Link to Dimethylsulfoxide?

Understanding the origin and distribution of electronic gap states in metal halide perovskite (MHP) thin films is crucial to the further improvement of the efficiency and long-term stability of MHP-based optoelectronic devices. In this work, the impact of Lewis-basic additives introduced in the precursor solution on the density of states in the perovskite bandgap is investigated. Ultraviolet photoemission spectroscopy and contact potential difference measurements are conducted on MHP thin films processed from dimethylformamide (DMF)-based solutions to which either no additive, dimethylsulfoxide (DMSO), or N-methylpyrrolidine-2-thione (NMPT) is added. The results show the presence of a density of states in the gap of methylammonium lead halide films processed from DMSO-containing solution. The density of gap states is either suppressed when the methylammonium concentration in mixed cation films is reduced or when NMPT is used as an additive, and eliminated when methylammonium (MA) is replaced with cesium or formamidinium (FA). These results are consistent with the notion that reaction products that result from DMSO reacting with MA+ in the precursor solution are responsible for the formation of gap states.

The anti-apoptotic role for p53 following exposure to ultraviolet light does not involve DDB2.

The p53 tumour suppressor is a transcription factor that can either activate or repress the expression of specific genes in response to cellular stresses such as exposure to ultraviolet light. The p53 protein can exert both pro- and anti-apoptotic effects depending on cellular context. In primary human fibroblasts, p53 protects cells from UV-induced apoptosis at moderate doses but this is greatly affected by the nucleotide excision repair (NER) capacity of the cells. The damage-specific DNA binding protein 2 (DDB2) is involved in NER and is associated with xeroderma pigmentosum subgroup E (XP-E). Importantly, DDB2 is also positively regulated by the p53 protein. To study the potential interplay between DDB2 and p53 in determining the apoptotic response of primary fibroblasts exposed to UV light, the expression of these proteins was manipulated in primary normal and XP-E fibroblast strains using human papillomavirus E6 protein (HPV-E6), RNA interference and recombinant adenoviruses expressing either p53 or DDB2. Normal and XP-E fibroblast strains were equally sensitive to UV-induced apoptosis over a broad range of doses and disruption of p53 in these strains using HPV-E6 or RNA interference led to a similar increase in apoptosis following exposure to UV light. In contrast, forced expression of p53 or DDB2 did not affect UV-induced apoptosis greatly in these normal or XP-E fibroblast strains. Collectively, these results indicate that p53 is primarily protective against UV-induced apoptosis in primary human fibroblasts and this activity of p53 does not require DDB2.

Extending the Photovoltaic Response of Perovskite Solar Cells into the Near-Infrared with a Narrow-Bandgap Organic Semiconductor.

Typical lead-based perovskites solar cells show an onset of photogeneration around 800 nm, leaving plenty of spectral loss in the near-infrared (NIR). Extending light absorption beyond 800 nm into the NIR should increase photocurrent generation and further improve photovoltaic efficiency of perovskite solar cells (PSCs). Here, a simple and facile approach is reported to incorporate a NIR-chromophore that is also a Lewis-base into perovskite absorbers to broaden their photoresponse and increase their photovoltaic efficiency. Compared with pristine PSCs without such an organic chromophore, these solar cells generate photocurrent in the NIR beyond the band edge of the perovskite active layer alone. Given the Lewis-basic nature of the organic semiconductor, its addition to the photoactive layer also effectively passivates perovskite defects. These films thus exhibit significantly reduced trap densities, enhanced hole and electron mobilities, and suppressed illumination-induced ion migration. As a consequence, perovskite solar cells with organic chromophore exhibit an enhanced efficiency of 21.6%, and substantively improved operational stability under continuous one-sun illumination. The results demonstrate the potential generalizability of directly incorporating a multifunctional organic semiconductor that both extends light absorption and passivates surface traps in perovskite active layers to yield highly efficient and stable NIR-harvesting PSCs.

Respiratory-gated CT as a tool for the simulation of breathing artifacts in PET and PET/CT.

Respiratory motion in PET and PET/CT blurs the images and can cause attenuation-related errors in quantitative parameters such as standard uptake values. In rare instances, this problem even causes localization errors and the disappearance of tumors that should be detectable. Attenuation errors are severe near the diaphragm and can be enhanced when the attenuation correction is based on a CT series acquired during a breath-hold. To quantify the errors and identify the parameters associated with them, the authors performed a simulated PET scan based on respiratory-gated CT studies of five lung cancer patients. Diaphragmatic motion ranged from 8 to 25 mm in the five patients. The CT series were converted to 511-keV attenuation maps which were forward-projected and exponentiated to form sinograms of PET attenuation factors at each phase of respiration. The CT images were also segmented to form a PET object, moving with the same motion as the CT series. In the moving PET object, spherical 20 mm mobile tumors were created in the vicinity of the dome of the liver and immobile 20 mm tumors in the midchest region. The moving PET objects were forward-projected and attenuated, then reconstructed in several ways: phase-matched PET and CT, gated PET with ungated CT, ungated PET with gated CT, and conventional PET. Spatial resolution and statistical noise were not modeled. In each case, tumor uptake recovery factor was defined by comparing the maximum reconstructed pixel value with the known correct value. Mobile 10 and 30 mm tumors were also simulated in the case of a patient with 11 mm of breathing motion. Phase-matched gated PET and CT gave essentially perfect PET reconstructions in the simulation. Gated PET with ungated CT gave tumors of the correct shape, but recovery was too large by an amount that depended on the extent of the motion, as much as 90% for mobile tumors and 60% for immobile tumors. Gated CT with ungated PET resulted in blurred tumors and caused recovery errors between -50% and +75%. Recovery in clinical scans would be 0%-20% lower than stated because spatial resolution was not included in the simulation. Mobile tumors near the dome of the liver were subject to the largest errors in either case. Conventional PET for 20 mm tumors was quantitative in cases of motion less than 15 mm because of canceling errors in blurring and attenuation, but the recovery factors were too low by as much as 30% in cases of motion greater than 15 mm. The 10 mm tumors were blurred by motion to a greater extent, causing a greater SUV underestimation than in the case of 20 mm tumors, and the 30 mm tumors were blurred less. Quantitative PET imaging near the diaphragm requires proper matching of attenuation information to the emission information. The problem of missed tumors near the diaphragm can be reduced by acquiring attenuation-correction information near end expiration. A simple PET/CT protocol requiring no gating equipment also addresses this problem.

Coupling of postural and manual tasks in expert performers.

The purpose of this study was to investigate the integration of bimanual rhythmic movements and posture in expert marching percussionists. Participants (N=11) performed three rhythmic manual tasks [1:1, 2:3, and 2:3-F (2:3 rhythm played faster at a self-selected tempo)] in one of three postures: sitting, standing on one foot, and standing on two feet. Discrete relative phase, postural time-to-contact, and coherence analysis were used to analyze the performance of the manual task, postural control, and the integration between postural and manual performance. Across all three rhythms, discrete relative phase mean and variability results showed no effects of posture on rhythmic performance. The complexity of the manual task (1:1 vs. 2:3) had no effect on postural time-to-contact. However, increasing the tempo of the manual task (2:3 vs. 2:3-F) did result in a decreased postural time-to-contact in the two-footed posture. Coherence analysis revealed that the coupling between the postural and manual task significantly decreased as a function of postural difficulty (going from a two-footed to a one-footed posture) and rhythmic complexity (1:1 vs. 2:3). Taken together, these results demonstrate that expert marching percussionists systematically decouple postural and manual fluctuations in order to preserve the performance of the rhythmic movement task.

Effects of application strategies of fumigant and nonfumigant nematicides on cantaloupe grown in deep sand soils in Florida.

A 2-year study was conducted in which three treatment tactics of oxamyl (at planting application, application every 2 weeks, and rescue applications, as determined by crop symptoms) were compared to fumigant treatments with methyl bromide, 1,3-dichloropropene (1,3-D), and 1,3-D plus chloropicrin for management of Meloidogyne spp. In 2002, treatments that included 1,3-D produced higher yields as determined both by number and weight of marketable fruit. All treatment tactics relying solely on oxamyl, at planting, scheduled treatments, and rescue, were not different from untreated controls for both marketable yield and number of fruit. Gall ratings in 2002 were lowest for 1,3-D at the 112-liters/ha rate, followed by 1,3-D at 84 liters/ha with and without oxamyl. All treatments of oxamyl, except when combined with 1,3-D, had gall ratings not different from untreated plots. In 2004, treatments of methyl bromide and 1,3-D plus chloropicrin had the highest total number of both marketable fruit and highest marketable yields. All treatment strategies relying solely on oxamyl had yields equivalent to the untreated controls. Mean root-gall ratings were lowest for methyl bromide plus chloropicrin and 1,3-D plus chloropicrin treatments. Root-gall ratings for all treatment tactics relying solely on oxamyl were not different from untreated controls.

Student learning styles in anatomy and physiology courses: Meeting the needs of nursing students.

Anatomy and Physiology is a core course in pre-registration nursing programs, yet many students have difficulty successfully negotiating the large volume of content and the complex concepts in these bioscience courses. Typically students perform poorly in these 'threshold' courses', despite multiple interventions to support student engagement. Investigation of the shortcomings in these courses, based on feedback from students indicated several key areas of difficulty in the course, especially focused around a relative lack of hands-on 'concrete' activities in laboratories and tutorials. To attempt to address this, academic and technical staff developed activities for students that promoted discussion and allowed students to interact easily and repetitively with content. Interactive tables and posters that needed to be labelled or 'filled-in' using pre-prepared Velcro dots, as well as pre-prepared flash cards to promote group work, were some examples of the activities used to enhance student experiences and promote hands-on learning. Over the academic year of 2013 these activities were introduced into the laboratory and tutorial classes for first year Bachelor of Nursing anatomy and physiology students. Staff and student participants positively rated implementation of these new activities on surveys, as they allowed them to explore the difficult aspects of anatomy and physiology, utilising various learning styles that may have been neglected in the past.

Determination of weighting functions for energy-weighted acquisition.

Energy-weighted acquisition (EWA) is an image filtering technique, with a different spatial filter (weighting function) for each energy. The imaging characteristics of EWA are governed by the weighting functions used during the acquisition of the image. The determination of weighting functions is more complicated than the determination of energy windows in conventional imaging because the number of degrees of freedom is much greater. A methodology by which weighting functions can be produced is described. The weighting function is determined by minimizing a generalized chi-square with variable contributions from coefficients quantifying key image characteristics, e.g., signal-to-noise ratio, spatial resolution, and scatter fraction. Varying the importance of these characteristics gives us a workable function-generation tool, able to address a variety of clinical needs. The resulting weighting functions exhibit good scatter reduction properties at various scatter depths, as demonstrated by measurements of line source response functions in a scattering medium at depths from 5 to 14 cm. Energy weighting can also be used to compensate for collimator penetration from high energy gamma rays. Weighting functions are tested in the laboratory using both planar and SPECT phantoms.

Energy-weighted acquisition of scintigraphic images using finite spatial filters.

Energy weighted acquisition (EWA) is a technique for improving image contrast by correcting for some of the blurring effects of Compton scattering within the patient. We outline image formation theory as it applies to energy weighting and present a pre-processing implementation that acquires images with real-number energy-dependent weighting functions of finite spatial extent. The effect of scattered radiation on quantitative accuracy, with and without EWA, is demonstrated with sheet and point sources at various depths. A planar phantom and a clinical 201TI study demonstrate enhanced contrast and edge definition. The performance of EWA in SPECT is shown by 99mTc and 123I phantom studies and a clinical 125I study.

Granuloma annulare-like eruption due to chronic Epstein-Barr virus infection.

A 32-year-old woman afflicted with a severe, chronic Epstein-Barr virus (CEBV) infection of 12 months' duration developed an unusual, granuloma annulare-like eruption. The cutaneous disorder, which paralleled the clinical course of her disease, was characterized by slightly raised, erythematous, annular lesions predominantly involving the face and arms, with sporadic involvement elsewhere. Histopathologic examination of biopsy material obtained from affected skin disclosed a granulomatous dermatitis. The patient's symptoms and cutaneous eruption resolved after systemic corticosteroid therapy. This eruption may represent a distinct cutaneous component of CEBV infection with clinically granuloma annulare-like features or the mere serendipitous association of CEBV infection and an unusual granulomatous dermatitis. Because of the unusual clinical appearance of the eruption and its clear correlation with disease activity, we speculate that it likely represents a distinct cutaneous condition, heretofore unreported, caused by CEBV infection.

Controlled-release indomethacin and sustained-release diclofenac sodium in the treatment of rheumatoid arthritis: a comparative controlled clinical trial.

The efficacy and tolerability of a new, controlled-release indomethacin (75 mg) tablet was compared to that of a sustained-release diclofenac sodium (100 mg) tablet in 84 patients with rheumatoid arthritis. The study was designed as a double-blind, double-dummy crossover trial, patients being allocated at random to receive 1 active tablet and 1 placebo tablet of the alternative medication at night for 4 weeks before being crossed over to the alternative treatment for a further 4 weeks. Patient and clinical assessments on entry and at the end of each treatment period showed that pain scores for day and night, duration of morning stiffness, requirement for escape analgesia (paracetamol) and treatment preference were similar for both treatments. Both preparations also significantly improved the degree of joint tenderness compared to baseline (p less than 0.001), as measured by a modified Ritchie Articular Index. Incidence and severity of side-effects were comparable, with a significant improvement in degree of constipation reported for both treatments compared to baseline (p less than 0.05). The incidence and severity of headache was statistically significantly worse (p less than 0.05) for controlled-release indomethacin; however, there was no difference in any other parameter of tolerability. It was concluded that controlled-release indomethacin tablets (75 mg) given as a single night-time dose were as efficacious and well tolerated as sustained-release diclofenac sodium (100 mg).

Ovarian Sertoli-Leydig cell tumor with retiform pattern.

Sertoli-Leydig cell tumors (SLCT) are sex cord-stromal tumors which exhibit testicular differentiation.1 They account for less than 0.2% of ovarian neoplasms in total but comprise 4% of ovarian tumors in females under 20 yrs of age.2 The morphological appearance of these tumors varies more widely than that of any other ovarian tumor except for the teratomas. Histologically they are now classified into 5 categories: well-differentiated, intermediately differentiated, poorly differentiated, heterologous and retiform.1 We describe the case of an ovarian Sertoli-Leydig cell tumor with retiform pattern in a 7 yr old girl.

Timing of lower extremity joint actions during treadmill running.

It has been suggested that a disruption in timing between the subtalar and knee joints may be a possible mechanism for knee injury. It has also been documented that shoe construction can alter rearfoot motion. The purpose of the study was to describe the relationship between the subtalar and knee joint actions during the support phase of treadmill running while wearing different shoes. Twelve healthy subjects ran in each of three running shoes with unique midsole durometers (C1, 70; C2, 55; C3, 45). High-speed video (200 Hz) of the rear and sagittal views of each subject/condition were taken during the last minute of a 5-min run. Retro-reflective markers were processed to determine the rearfoot angle and the sagittal view knee angle. The shoes were also subjected to a midsole material impact test. The impact test results indicated a linear trend in peak g and time to peak g across midsoles with the firmer midsole having a greater peak g and a shorter time to peak g. The results of the kinematic analysis indicated that there were no significant differences among the shoe conditions for the knee flexion parameters. However, there were significant differences in both the magnitude and the time to maximum pronation between the two firmer midsole conditions (C1 and C2) and the softer midsole condition (C3), indicating a nonlinear trend for these parameters. The softer midsole exhibited greater pronation values and a shorter time to maximum pronation.(ABSTRACT TRUNCATED AT 250 WORDS)

Predicting the minimal energy costs of human walking.

Preferred stride frequency (PSF) of human walking has been shown to be predictable as the resonant frequency of a force-drive harmonic oscillator (FDHO). The purpose of this study was to determine whether walking at the PSF and FDHO leads to minimal metabolic and mechanical costs. Subjects walked on a level treadmill at the PSF, FDHO, and frequencies above and below. Effects of stride length (SL) and speed (S) were assessed by two conditions, one in which SL was constant and the other in which S was constant. The predictability of PSF from resonance was replicated. Walking at the PSF and FDHO frequencies resulted in metabolic costs which were not significantly different (P greater than 0.05). A U-shaped oxygen consumption curve was observed with the minimum at the PSF and FDHO conditions when S was constant. A two-component curve in which a breakpoint was observed was found in the SL constant condition. A significant increase in metabolic cost was observed above the PSF/FDHO (P less than 0.01). Internal work (power) values were not significantly different between walking frequencies for the S constant condition. In the SL constant condition, internal work values showed linear increases as frequency increased. It was concluded that PSF of walking arises from the interface of the resonance properties of the limbs as oscillators and the tendency of biological systems to self-optimize.

Energy absorption of impacts during running at various stride lengths.

PURPOSE: The foot-ground impact experienced during running produces a shock wave that is transmitted through the human skeletal system. This shock wave is attenuated by deformation of the ground/shoe as well as deformation of biological tissues in the body. The goal of this study was to investigate the locus of energy absorption during the impact phase of the running cycle. METHODS: Running speed (3.83 m x s[-1]) was kept constant across five stride length conditions: preferred stride length (PSL), +10% of PSL, -10% of PSL, +20% of PSL, and -20% of PSL. Transfer functions were generated from accelerometers attached to the leg and head of ten male runners. A rigid body model was used to estimate the net energy absorbed at the hip, knee, and ankle joints. RESULTS: There was an increasing degree of shock attenuation as stride length increased. The energy absorbed during the impact portion of the running cycle also increased with stride length. Muscles that cross the knee joint showed the greatest adjustment in response to increased shock. CONCLUSION: It was postulated that the increased perpendicular distance from the line of action of the resultant ground reaction force to the knee joint center played a role in this increased energy absorption.

Effect of internal work on the calculation of optimal pedaling rates.

The purpose of this study was to calculate optimal pedaling rates based upon external work (EW) rate and mechanical work (MW) rate criteria that respectively exclude and include the internal work (IW) rate of the lower limbs. Metabolic and kinematic data were collected as 12 males pedaled an ergometer at rates of 40, 60, 80, and 98 rpm while producing external power outputs of 49, 98, and 146 W. Energy expenditure (EE) was calculated from steady rate oxygen uptake and respiratory exchange ratio values. The IW rate was determined from digitized kinematic data by modeling the thigh, shank, and foot as a three-segment linked system and calculating their changes in potential, translational kinetic, and rotational kinetic energy. The EW rate was calculated from the observed pedaling rate and the ergometer resistance. The MW rate was defined as the sum of the EW rate and IW rate. At each level of external power output, the MW rate increased linearly with pedaling rate increments while the EE displayed a curvilinear relationship. Both gross efficiency (GE = EW rate/EE) and mechanical efficiency (ME = MW rate/EE) responded quadratically to pedaling rate treatments but a repeated measures ANOVA revealed significant differences in their beta 0, beta 1, and beta 2 regression coefficients. Optimal pedaling rates calculated from ME were consistently higher (82 to 101 rpm) than those determined from GE (35 to 57 rpm). The pedaling rates that optimized ME, but not GE, are similar to the rates reported to be biomechanically optimal and preferred by trained cyclists. This study demonstrates that the choice of a work rate criterion can alter the meaning and interpretation of metabolic data.

The effect of comments about shoe construction on impact forces during walking.

UNLABELLED: Comparisons of ground reaction forces (GRF) during gait are not typically conducted with blinding of the varied shoe characteristic, raising concerns related to the existence of a placebo effect, or a subject response based on a perceived expectation of change. PURPOSE: To determine whether investigator comments on shoe construction influenced GRF measures and ratings of shoe cushioning during walking. METHODS: 19 female college students volunteered for a study presented as a test of a new shoe material. The study involved walking (2.5 m x s(-1)) under three shoe conditions (SC). Shoes in SC2 and SC3 were harder than those in SC1, but shoes in SC1 and SC3 looked similar. Subjects in a mislead group (N = 9) were told SC1 and SC3 were baseline measures in a standard shoe, with SC2 misleadingly described as a shoe constructed of unique new material. A control group performed the same three conditions without investigator description. GRF data were collected for 10 trials for each subject in each condition, and subjects rated the perceived cushioning of each shoe. GRF data and perceived cushioning scores were analyzed using mixed-factor (group by shoe) ANOVA. RESULTS: A significant shoe main effect was found for loading rate. Post hoc tests identified the difference between SC1 and both SC2 and SC3. The group main effect was not significant for any dependent variable. CONCLUSIONS: Results suggest that, as a group, GRF data and cushioning scores are not affected by investigator comments that do not match shoe construction characteristics. However, ratings of perceived shoe cushioning by some individual subjects reflected investigator comments and not the vertical GRF variables.

A comparison between free-weight and isokinetic bench pressing.

The purpose of the study was to evaluate selected parameters describing performance characteristics of a free-weight and isokinetic bench press. A secondary purpose was an attempt to clarify the technique requirements essential for a successful lift. Parameters describing the free-weight condition were generated from cinematographic data (150 fps) for five trials each at 90 and 75% of the subject's maximal performance (1RM). Isokinetic data were obtained from an instrumented Cybex Power Bench Press at two speeds corresponding to the average speeds for the free-weight conditions. Despite differences, accommodation appeared to occur for both methods when the lifts were performed maximally. A "sticking region" was defined as the portion of the free-weight activity when the subjects' force application was less than the weight of the bar. No significant difference (P less than 0.05) was observed between the 90% 1RM (26.02%) and 75% 1RM (26.94%) mean relative time values for these regions. For the Cybex device, the percentage of the activity which was isokinetic was longer for the slower speeds of rotation (0.47 rad X s-1 = 70%) and steadily decreased until the movement was only 50% isokinetic at 1.74 rad X s-1. The observed relationships between applied force-time data along with anatomical considerations suggest an ideal technique for the lift.