cssi/SciSciGPT-SciSciNet huggingface dataset:
Digital light field photography

Focusing images well has been difficult since the beginnings of photography in 1839. Three manifestations of the problem are: the chore of having to choose what to focus on before clicking the shutter, the awkward coupling between aperture size and depth of field, and the high optical complexity of lenses required to produce aberration-free images. These problems arise because conventional cameras record only the sum of all light rays striking each pixel on the image plane. This dissertation presents a unified solution to these focus problems by instead recording the light field inside the camera: not just the position but also the direction of light rays striking the image plane. I describe the design, prototyping and performance of a digital camera that records this light field in a single photographic exposure. The basic idea is to use an array of microlenses in front of the photosensor in a regular digital camera. The main price behind this new kind of photography is the sacrifice of some image resolution to collect directional ray information. However, it is possible to smoothly vary the optical configuration from the light field camera back to a conventional camera by reducing the separation between the microlenses and photosensor. This allows a selectable trade-off between image resolution and refocusing power. More importantly, current semiconductor technology is already capable of producing sensors with an order of magnitude more resolution than we need in final images. The extra ray directional information enables unprecedented capabilities after exposure. For example, it is possible to compute final photographs that are refocused at different depths, or that have extended depth of field, by re-sorting the recorded light rays appropriately. Theory predicts, and experiments corroborate, that blur due to incorrect focus can be reduced by a factor approximately equal to the directional resolution of the recorded light rays. Similarly, digital correction of lens aberrations re-sorts aberrant light rays to where they should ideally have converged, improving image contrast and resolution. Future cameras based on these principles will be physically simpler, capture light more quickly, and provide greater flexibility in finishing photographs.
Metabolic dynamics in cells viewed as multilayered, distributed, mass‐energy‐information networks

The role of mathematical models in integrating available information on metabolic networks is highlighted. General modeling and other quantitative methodologies currently available are critically reviewed and the potential contributions of proteomics complemented by theoretical concepts derived from these modeling frameworks are assessed. The multilayered, distributed, view of cells increases the necessity of a more fundamental understanding of the dynamics of complex reaction networks as well as cytoplasmic organization, on cell physiology. The future of mathematical modeling will be largely determined by the trade-off between completeness and understandability. Keywords: mathematical models; metabolic flux and control analysis; signaling; proteomics; cytoplasmic organization; pathophysiology; robustness; critical behavior
A phage display-selected peptide inhibitor of Agrobacterium vitis polygalacturonase

Summary Agrobacterium vitis, the causal agent of crown gall of grapevine, is a threat to viticulture worldwide. A major virulence factor of this pathogen is polygalacturonase, an enzyme that degrades pectin components of the xylem cell wall. A single gene encodes for the polygalacturonase gene. Disruption of the polygalacturonase gene results in a mutant that is less pathogenic and produces significantly fewer root lesions on grapevines. Thus, the identification of peptides or proteins that could inhibit the activity of polygalacturonase could be part of a strategy for the protection of plants against this pathogen. A phage-displayed combinatorial peptide library was used to isolate peptides with a high binding affinity to A. vitis polygalacturonase. These peptides showed sequence similarity to regions of Oryza sativa (EMS66324, Japonica) and Triticum urartu (NP_001054402, wild wheat) polygalacturonase-inhibiting proteins (PGIPs). Furthermore, these panning experiments identified a peptide, SVTIHHLGGGS, which was able to reduce A. vitis polygalacturonase activity by 35% in vitro. Truncation studies showed that the IHHL motif alone is sufficient to inhibit A. vitis polygalacturonase activity.
Are Synonymous Substitutions in Flowering Plant Mitochondria Neutral

Angiosperm mitochondrial genes appear to have very low mutation rates, while non-gene regions expand, diverge, and rearrange quickly. One possible explanation for this disparity is that synonymous substitutions in plant mitochondrial genes are not truly neutral and selection keeps their occurrence low. If this were true, the explanation for the disparity in mutation rates in genes and non-genes needs to consider selection as well as mechanisms of DNA repair. Rps14 is co-transcribed with cob and rpl5 in most plant mitochondrial genomes, but in some genomes, rps14 has been duplicated to the nucleus leaving a pseudogene in the mitochondria. This provides an opportunity to compare neutral substitution rates in pseudogenes with synonymous substitution rates in the orthologs. Genes and pseudogenes of rps14 have been aligned among different species and the mutation rates have been calculated. Neutral substitution rates in pseudogenes and synonymous substitution rates in genes are significantly different, providing evidence that synonymous substitutions in plant mitochondrial genes are not completely neutral. The non-neutrality is not sufficient to completely explain the exceptionally low mutation rates in land plant mitochondrial genomes, but selective forces appear to play a small role.
Effective diffusion distance of nitric oxide in the microcirculation

Despite its well-documented importance, the mechanism for nitric oxide (NO) transport in vivo is still unclear. In particular, the effect of hemoglobin-NO interaction and the range of NO action hav...
Urinary Calcium Determination Three Newer Methods Compared with the Clark-Collip Procedure

A manual titrimetric EDTA-calcium technic, an automated fluorometric EDTA-calcium technic, and the atomic absorption spectrometric technic were compared with the Clark-Collip procedure for determination of urinary calcium. All three were demonstrated to give adequately comparable results. Atomic absorption spectrometry compared best; it also enjoys clear advantages of speed and simplicity.
Distributed strain measurement in a rectangular plate using an array of optical fiber sensors

Single mode optical fiber waveguide has been used to determine the two-dimensional strain distribution on a simply supported rectangular plate. Each of the fifty individual fibers in the rectangular grid array attached to one surface of the plate yields a measurement of the strain integrated along the length of that fiber on the specimen. By using similar sensor information from all of the fibers, both the functional form and the amplitude of the distribution may be determined. Limits on the dynamic range and spatial resolution are indicated. Applications in the measurement of internal strain and the monitoring of physically small critical-structural components are suggested.
Observations of energetic neutral atoms by the EPIC instrument — First result on the composition

Energetic neutral atoms (ENAs) were detected by the Energetic Particles and Ion Composition (EPIC) instrument on the Geotail spacecraft during a magnetic storm on October 29–30, 1994. The energetic particles could be identified as neutrals because the direction of the particle flux steadily tracked the direction of the Earth and was uncorrelated with the changing orientation of the ambient magnetic field as the spacecraft viewed the dayside magnetosphere for ∼ 16 hours. These observations provide the first composition measurements of ENAs, yielding the storm-time evolution of ENA fluxes of hydrogen, helium, and oxygen separately as well as their energy spectra. ENA fluxes and the rate of recovery of Dst are both roughly steady, consistent with charge-exchange being a significant energy loss process for the storm-time ring current. For total energies above 200 keV, the intensity of ENA oxygen is the highest, followed by hydrogen, and then by helium. These observations enable us to deduce the line-of-sight (LOS) integrals of the products nH jion, where nH = hydrogen geocorona density, jion = differential ion flux for ion species H+, He+, and O+ at energies between ∼60 and ∼600 keV.
Zaphod Beeblebrox's brain and the fifty-ninth row of Pascal's triangle

(1992). Zaphod Beeblebrox's Brain and the Fifty-ninth Row of Pascal's Triangle. The American Mathematical Monthly: Vol. 99, No. 4, pp. 318-331.
Serotonin transporter (5-HTT) gene and bipolar affective disorder.

Interactions with antidepressants, as well as other biochemical evidence, implicate the serotonin transporter 5-HTT in the etiology of affective disorders. However, genetic studies have produced conflicting results concerning an association of 5-HTT with bipolar disorder. We examined a variable number tandem repeat in the regulatory region of this gene to investigate the possible contribution of 5-HTT to bipolar disorder susceptibility in a 22-pedigree series. By affected-sib-pair analysis and the transmission/disequilibrium test, we found no significant linkage or association of 5-HTT to bipolar disorder. During the course of this study, we adapted a PCR technique designed to amplify long templates to replicating long GC stretches with complex structure. We also refined the location of 5-HTT by radiation hybrid mapping, placing the locus between D17S1294 and SHGC-11022 on 17q11.2. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 81:37–40, 1998. © 1998 Wiley-Liss, Inc.
The Fallacy of Misplaced Concreteness

Cambridge mathematician and Harvard philosopher Alfred North Whitehead provided excellent advice for scientists. He said, “Seek simplicity but distrust it” (1). Scientists who like to explain observed phenomena by reduction, and to model experimental results using (mostly mechanical) models, often follow the first part of Whitehead’s sentence while forgetting the second.
Review of techniques to remove a Foley catheter when the balloon does not deflate

Failure of a Foley balloon to deflate may be caused by a faulty valve mechanism, blockage of the inflation channel, or, rarely, crystallization of the fluid within the balloon. We discuss the approach to successful management and present a stepwise algorithm to remove the catheter safely and expeditiously.
Cytokine regulation of adenylate cyclase activity in LLC-PK1 cells

Cytokine regulation of adenylate cyclase activity in LLC-PK 1 cells. Although several cytokines have been demonstrated to exert pleiotropic responses, there is little information on cytokine regulation of renal tubular epithelial cell function. In the present studies, we find that both T cell-derived (tumor necrosis factor-β and interleukins 2 and 3) and monocyte/macrophage derived (tumor necrosis factor alpha and interleukin 1β) cytokines promote basal, arginine vasopressin- and forskolin-stimulated adenylate cyclase activity in cultured LLC-PK 1 cells. No effect of TNF, IL-1β, and IL-2 to stimulate protein kinase C activity was observed. TNF-β, IL-1β and IL-2 also modestly stimulated 3H release from 3 H-arachidonic acid labeled cells. Mepacrine, a phospholipase A inhibitor, prevented TNF-β stimulation of 3 H release from 3 H-arachidonic acid labeled cells and TNF-β potentiation of adenylate cyclase activity. TNF-β potentiation of adenylate cyclase activity and stimulation of 3 H release from 3 H arachidonic acid labeled cells was not prevented by pertussis toxin. These results demonstrate that several cytokines can stimulate adenylate cyclase activity while not affecting protein kinase C activity in cultured renal tubular epithelial cells. The effect of TNF-β to stimulate adenylate cyclase appears to occur independent of pertussis toxin-sensitive substrate and may involve activation of phospholipase A.
Expression of human genes for adenine phosphoribosyltransferase and hypoxanthine-guanine phosphoribosyltransferase after genetic transformation of mouse cells with purified human DNA.

Human DNA purified from HeLa cells and from three strains of skin fibroblasts was precipitated with calcium phosphate and added to mouse cells that were deficient in adenine phosphoribosyltransferase (APRT) and hypoxanthine phosphoribosyltransferase (HPRT). Selection for cells possessing either of the phosphoribosyltransferases was imposed by blocking de novo synthesis of purine nucleotides with azaserine in a medium supplemented with adenine and hypoxanthine. The frequency of colony formation after selection was 1.7×10−7−3.3×10−6. Excepting some azaserine-resistant colonies that appeared only in the first experiment and infrequent revertants expressing mouse APRT, all characterized clones expressed the human forms of APRT or HPRT according to the criteria of specific immunoprecipitation and electrophoretic mobility. The frequency of transfer of the human APRT gene was much greater than that of HPRT. Transfer efficiency was not significantly reduced when HeLa DNA was sheared to 6.5–13.5 kb size or when the donor DNA was isolated from a transferent that expressed human APRT.
Book reviews: the new wave - concurrent programming

Until now, concurrent programming has been widely used primarily on systems that do a lot of processing - for example, Web servers. With the advent of dual-core processors, however, concurrent programming is becoming the name of the game, even for PC applications. Creating Components: Object Oriented, Concurrent, and Distributed Computing in Java by Charles W. Kann is a good reference for programming concurrency using objects. The book is based on Java and uses threads, interfaces, and exceptions extensively to describe system design and management.
Double dissociation between long-term depression and dendritic spine morphology in cerebellar Purkinje cells.

Experiments in hippocampal area CA1 suggest that long-term potentiation could be associated with spine addition and enlargement, and long-term depression (LTD) with spine shrinkage and loss. Is this a general principle of synaptic plasticity? We used two-photon microscopy to measure dendritic spines in rat cerebellar Purkinje cells. Neither local synaptic induction of LTD nor global chemical induction of LTD changed spine number or size. Conversely, a manipulation that evoked persistent dendritic spine retraction did not alter parallel fiber–evoked excitatory postsynaptic currents.
Activating transcription factor 6 plays protective and pathological roles in steatosis due to endoplasmic reticulum stress in zebrafish.

Many etiologies of fatty liver disease (FLD) are associated with the hyperactivation of one of the three pathways composing the unfolded protein response (UPR), which is a harbinger of endoplasmic reticulum (ER) stress. The UPR is mediated by pathways initiated by PRKR-like endoplasmic reticulum kinase, inositol-requiring 1A/X box binding protein 1, and activating transcription factor 6 (ATF6), and each of these pathways has been implicated to have a protective or pathological role in FLD. We used zebrafish with FLD and hepatic ER stress to explore the relationship between Atf6 and steatosis. A mutation of the foie gras (foigr) gene caused FLD and hepatic ER stress. The prolonged treatment of wild-type larvae with tunicamycin (TN), which caused chronic ER stress, phenocopied foigr. In contrast, acute exposure to a high dose of TN robustly activated the UPR but was less effective at inducing steatosis. The sterol regulatory element binding protein transcription factors were not required for steatosis in any of these models. Instead, depleting larvae of active Atf6 either through a membrane-bound transcription factor peptidase site 1 mutation or an atf6 morpholino injection protected them against steatosis caused by chronic ER stress, but exacerbated steatosis caused by acute TN treatment. Conclusion: ER stress causes FLD. A loss of Atf6 prevents steatosis caused by chronic ER stress but can also potentiate steatosis caused by acute ER stress. This demonstrates that Atf6 can play both protective and pathological roles in FLD. (HEPATOLOGY 2011;)
The Rhetoric of Sentimental Greeting Card Verse

I suspect that many people who buy sentimental greeting card verse have the same preconceived ideas about such verse that I had before I began a serious study of it a few years ago. To my mind, greeting card verse was a trite and trivial form of poetry, filled with flowery language, poetic diction, and figures of speech, appealing to emotions in excess of the occasion-artificial, affected, and insincere. To my surprise, however, I discovered that greeting card verse, although often written in meter and rhyme, is not poetry, nor is it intended to be, but a rhetorical composition, a message transmitted from one person to another. Although its rhymes and meters are frequently trite (this may account for its wholesale condemnation), the sentiments it expresses, although commonplace, are seldom trivial. It uses few figures of speech, little or no poetic diction, and almost no flowery language. Nor are its emotions in excess of the occasion. The sentiments and emotions it expresses are no different than those that you and I might express at a wedding, a graduation, an anniversary, or a birthday, or at Christmas, New Year's, or Easter-good luck, congratulations, I love you, I'm thinking of you, have a joyous holiday, and so forth. Finally, greeting card verse is neither artificial, affected, nor insincere, but straightforward, genuine, and sincere. In fact, it exemplifies beautifully an important kind of ceremonial discourse, and I can think of no better way of introducing writers to the ancient art of epideictic discourse than through a careful analysis and understanding of the rhetorical strategies used by writers of greeting card verse. Paradoxically, greeting card verse is both universal and particular. The message of greeting card verse must be general enough to fit representative rhetorical situations (Quinn 22), yet particular enough to fit immediate occasions. Like proverbs, maxims, quotations, and anecdotes, when they are decontextualized and put into collections, greeting card verse is decontextualized when it is put on racks of cards in card shops, drug stores, and supermarkets. Under appropnate circumstances, however, the person who buys greeting card verse recontextualizes it, appropriates it to his or her own intention, and sends it to someone else as a personal message. As a result, there is a dialogic relationship set up between the writer's intention and the sender's intention, between the writer's words and the sender's words. But as Mikhail Bakhtin has pointed out, do not all of the
A nonlinear approach to tracking slow-time-scale changes in movement kinematics.

Degenerative processes like repetitive strain injuries (RSIs) cause normal movement patterns to change slowly over time. Accurately tracking how these disease/injury processes evolve over time and predicting their future progression could allow early intervention and prevent further deterioration. However, these processes often cannot be measured directly and first-principles models of these processes and how they affect movement control are highly complex and difficult to derive analytically. This study was conducted to determine if algorithms developed to track damage accumulation in mechanical systems without requiring firstprinciples models or direct measurements of the damage itself could also track a similar ‘‘hidden’’ process in a biomechanical context. Five healthy adults walked on a motorized treadmill at their preferred speed, while the treadmill inclination angle was slowly increased from 01 (level) to approximately +81. Sagittal plane kinematics for the left hip, knee, and ankle joints were computed. The treadmill inclination angle was independently recorded and defined the ‘‘damage’’ to be tracked. Scalar tracking metrics were computed from the lower extremity walking kinematics. These metrics exhibited strong cubic relationships with treadmill inclination (88.9%pr 2 p98.2%; po0.001). These results demonstrate that the proposed approach may also be well suited to tracking and predicting slow-time-scale degenerative biological processes like muscle fatigue or RSIs. This possibility is potentially quite powerful because it suggests that easily obtainable biomechanical data can provide unique and valuable insights into the dynamics of ‘‘hidden’’ biological processes that cannot be easily measured themselves. r 2006 Elsevier Ltd. All rights reserved.
Monozygotic Twins With Klinefelter's Syndrome Discordant For Systemic Lupus Erythematosus And Symptomatic Myasthenia Gravis

Monozygotic twins with Klinefelter's syndrome were evaluated for two distinct illnesses. One subject had clinical and serologic evidence of systemic lupus erythematosus and no symptoms of muscle weakness. His identical twin had typical symptoms and laboratory evidence of myasthenia gravis. Antibodies to acetylcholine receptors were present in both subjects. These patients are discussed in relation to genetic, hormonal, and immunologic mechanisms involved in the pathogenesis of these two disorders.
A Rhetorical Recovery: Self-Avowal and Self-Displacement in the Life, Fiction, and Nonfiction of Marcet Haldeman-Julius, 1921–1936

Co-owning and writing for one of the world's largest private publishing houses in the 1920s and 1930s, Marcet Haldeman-Julius's (1887–1941) position should have guaranteed her a place in American women's literary history. Haldeman-Julius's socialist and feminist exigency, though, was elided by a complex and emotionally abusive marriage to her editor and publisher, Emanuel Haldeman-Julius, whose final approval represented her chance to effectively enter the public sphere. This study recovers Haldeman-Julius's work and traces her significant attempts to negotiate the paradox of writing as a feminist in ways rhetorically coded to escape certain audiences and to activate others.
Safety and Efficacy of Armodafinil in the Treatment of Excessive Sleepiness

Objective: To review the efficacy and safety of armodafinil for the treatment in patients with excessive sleepiness. Data sources: Literature was accessed via MEDLINE (1966–February 2011) and EMBASE (1980–February 2011) using the medical subject heading terms armodafinil and sleep. Study selection and data extraction: All English-language, peer-reviewed publications were analyzed for relevance. Studies appropriate to the objective were evaluated if they prospectively assessed the effectiveness of armodafinil in patients with excessive sleepiness in a multiple-dose, comparator trial. The literature search identified published reports of 7 randomized, placebo-controlled studies. Data synthesis: Armodafinil is a wakefulness-promoting agent used in the treatment of patients with excessive sleepiness and is the R-enantiomer of modafinil. Studies have demonstrated that armodafinil may be effective and safe when used in patients with obstructive sleep apnea, circadian rhythm disorders, and narcolepsy. Although the studies identified had limited sample sizes, they consistently demonstrated improvement on various efficacy rating scales for sleep. Study durations ranged from 3 days to 12 weeks, with doses ranging from 50 mg to 250 mg daily. The most common adverse effects associated with armodafinil therapy were headache, nausea, diarrhea, dizziness, and anxiety, although increases in systolic blood pressure and pulse rate were also reported. Conclusion: Current evidence suggests that armodafinil significantly improves wakefulness in patients with excessive sleepiness in studies up to 12 weeks. Long-term effectiveness and safety cannot be adequately determined at this time. Although armodafinil should be considered safe for use, health-care providers should monitor for adverse effects, particularly cardiovascular complications.
Wing Shape as an Indicator of Larval Rearing Conditions for Aedes albopictus and Aedes aegypti (Diptera: Culicidae)

Estimating a mosquitoOs vector competence, or likelihood of transmitting disease, if it takes an infectious bloodmeal, is an important aspect of predicting when and where outbreaks of infectious diseases will occur. Vector competence can be affected by rearing temperature and inter- and intraspeciÞc competition experienced by the individual mosquito during its larval development. This research investigates whether a new morphological indicator of larval rearing conditions, wing shape, can be used to distinguish reliably temperature and competitive conditions experienced during larval stages. Aedes albopictus (Skuse) and Aedes aegypti (L.) (Diptera: Culicidae) larvae were reared in low intraspeciÞc, high intraspeciÞc, or high interspeciÞc competition treatments at either 22 or 32C. The right wing of each dried female was removed and photographed. Nineteen landmarks and 20 semilandmarks were digitized on each wing. Shape variables were calculated using geometric mor- phometric software. Canonical variate analysis, randomization multivariate analysis of variance, and visualization of landmark movement using deformation grids provided evidence that although semilandmark position was signiÞcantly affected by larval competition and temperature for both species, the differences in position did not translate into differences in wing shape, as shown in deformation grids. Two classiÞcation procedures yielded success rates of 26 Ð 49%. Accounting for wing size produced no increase in classiÞcation success. There seemed to be a signiÞcant relationship between shape and size. These results, particularly the low success rate of classiÞcation based on wing shape, show that shape is unlikely to be a reliable indicator of larval rearing competition and temperature conditions for Ae. albopictus and Ae. aegypti.
Cycle of earthquake‐induced aggradation and related tidal channel shifting, upper Turnagain Arm, Alaska, USA

Aggradation of intertidal sediment in upper Turnagain Arm, a macrotidal estuary located in southern Alaska near Anchorage, began because of subsidence caused by sediment consolidation and tectonic lowering of the land during the earthquake of March 27, 1964. At the head of the Arm, decrease in percent sand of surface sediments with time and return of rodents, pulmonate gastropods, trees, bushes, and grasses to the intertidal region, indicate that the rate of sediment deposition has slowed and the Upper Turnagain Arm area has returned to a state of preearthquake equilibrium only 17 years after the event. Comparison of channel locations before and after the earthquake indicates the possibility of regional postseismic tilting of the estuary.
Influence of Growth Rate and Feed Intake on the Occurrence of Nutritional Muscular Dystrophy in the Chick

Abstract THE development of nutritional muscular dystrophy in the growing chick is known to be modified by a number of nutritional factors. Dam et al. (1952) showed that concomitant dietary deficiencies of both vitamin E and sulfur amino acids are necessary for the appearance of this disorder. In addition, inclusion of selenium in the diet has been reported to reduce although never completely prevent the incidence of muscular dystrophy (Dam and Sondergaard, 1957; Nesheim and Scott, 1958). The use of unusually high dietary levels of antioxidants other than vitamin E may also prevent the development of muscular dystrophy (Machlin and Shalkop, 1956). Recently Calvert et al. (1964) have shown that dietary linoleic acid is necessary for the appearance of muscular dystrophy, and that chicks fed linoleic acid-free diets do not show symptoms of the disease regardless of the deficiency of vitamin E and sulfur amino acids. Unpublished results from our laboratory…
Electrochemical analysis of separators used in single-chamber, air-cathode microbial fuel cells

Abstract Polarization, solution-separator, charge transfer, and diffusion resistances of clean and used separator electrode assemblies were examined in microbial fuel cells using current–voltage curves and electrochemical impedance spectroscopy (EIS). Current–voltage curves showed the total resistance was reduced at low cathode potentials. EIS results revealed that at a set cathode potential of 0.3 V diffusion resistance was predominant, and it substantially increased when adding separators. However, at a lower cathode potential of 0.1 V all resistances showed only slight differences with and without separators. Used separator electrode assemblies with biofilms had increased charge transfer and diffusion resistances (0.1 V) when one separator was used; however, charge transfer resistance increased, and diffusion resistance did not appreciably change with four separators. Adding a plastic mesh to compress the separators improved maximum power densities. These results show the importance of pressing separators against the cathode, and the adverse impacts of biofilm formation on electrochemical performance.
Estimating the sensitivity of state tax revenue to cyclical and wealth effects

In this study, we estimate the elasticities of alternative sources of state tax revenue relative to the economy, as measured by GSP, and to wealth, as measured by the S&P500. Next, efficient tax frontiers are estimated for each state by minimizing the standard deviation, given the current average growth rate of revenues. It is shown how states could attain the same expected growth rate of tax revenues with less volatility by modifying the composition of their existing tax structures. In most cases, corporate income taxes are found to reduce efficiency due to their high volatility without a correspondingly high growth rate.
Tensilely Strained Germanium Nanomembranes for Direct-Bandgap Infrared Light Emission

The development of practical light sources based on group-IV semiconductors is a major outstanding goal of optoelectronics research, as a way to enable the continued integration of electronic and photonic functionalities on a CMOS compatible platform. However, this goal is severely complicated by the indirect energy bandgap of silicon, germanium, and related alloys. A possible solution is provided by the ability of biaxial tensile strain in Ge to lower the conduction-band edge at the direct (Γ) point relative to the L-valley minima, until at a strain of about 1.9% the fundamental bandgap becomes direct. Here we show that, by virtue of their ultrasmall thicknesses, Ge nanomembranes under externally applied mechanical stress are capable of accommodating such relatively high strain levels (up to over 2%). With this approach, we have demonstrated strong strain-enhanced Ge photoluminescence accompanied by a large strain-induced red shift in emission wavelength. A theoretical model of the emission properties of tensilely strained Ge has also been developed and applied to the measured high-strain luminescence spectra, providing evidence of population inversion. Finally, mechanically flexible photonic-crystal cavities have been developed on these nanomembranes, and used to demonstrate particularly large (20×) strain-induced enhancements in radiative efficiency, together with the observation of luminescence signatures associated with band-edge cavity modes. These results are promising for the development of group-IV semiconductor lasers for the technologically important short-wave infrared spectral region.
Some basic problems in stress wave dominated fracture

Problems of characterizing the stress wave induced stress field around the crack tip and ensuing crack propagation behavior are described. After stating the assumptions underlying an idealized model of brittle, dynamic fracture we review experimentally observed deviations from such idealized behavior. Such deviations are ascribed to the development of numerous microcracks in the crack tip region. These microcracks determine the crack initiation process, the speed of crack growth and the branching phenomenon. Also we examine critically the contention that there exists a unique relation which links instantaneous crack speed to the instantaneous stress intensity factor in brittle solids. That question highes materially on limitations of current measurement techniques.
Cyclobutane Pyrimidine Dimers and Bulky Chemical DNA Adducts Are Efficiently Repaired in Both Strands of Either a Transcriptionally Active or Promoter-deleted APRT Gene

Both prokaryotic and eukaryotic cells have the capacity to repair DNA damage preferentially in the transcribed strand of actively expressed genes. However, we have found that several types of DNA damage, including cyclobutane pyrimidine dimers (CPDs) are repaired with equal efficiency in both the transcribed and nontranscribed strands of the adenine phosphoribosyltransferase (APRT) gene in Chinese hamster ovary cells. We further found that, in two mutant cell lines in which the entire APRT promoter region has been deleted, CPDs are still efficiently repaired in both strands of the promoterless APRT gene, even though neither strand appears to be transcribed. These results suggest that efficient repair of both strands at this locus does not require transcription of the APRT gene. We have also mapped CPD repair in exon 3 of the APRT gene in each cell line at single nucleotide resolution. Again, we found similar rates of CPD repair in both strands of the APRT gene domain in both APRT promoter-deletion mutants and their parental cell line. Our findings suggest that current models of transcription-coupled repair and global genomic repair may underestimate the importance of factors other than transcription in governing the efficiency of nucleotide excision repair.
Neural control of rhythmic arm movements

In this paper we present an approach to robot arm control based on exploiting the dynamical properties of a simple neural network oscillator circuit coupled to the joints of an arm. The entrainment and input/output properties of the oscillators are used to perform a variety of tasks with the same architecture, without any modeling of the arm or its environment. The approach is implemented on two real robot arms, and has been used to tune into the resonant frequency of pendulums, perform multi-joint coordinated motion by turning cranks, and exploit the dynamics of a 'Slinky' toy to coordinate the motion of two arms. By exploiting the coupling between the physical arm and the neural oscillator, a range of complex behaviors can be achieved with a very simple system.
Coupling of Retinal, Protein, and Water Dynamics in Squid Rhodopsin

The light-induced isomerization of the retinal from 11-cis to all-trans triggers changes in the conformation of visual rhodopsins that lead to the formation of the activated state, which is ready to interact with the G protein. To begin to understand how changes in the structure and dynamics of the retinal are transmitted to the protein, we performed molecular dynamics simulations of squid rhodopsin with 11-cis and all-trans retinal, and with two different force fields for describing the retinal molecule. The results indicate that structural rearrangements in the binding pocket, albeit small, propagate toward the cytoplasmic side of the protein, and affect the dynamics of internal water molecules. The sensitivity of the active-site interactions on the retinal force-field parameters highlights the coupling between the retinal molecule and its immediate protein environment.
MR imaging of articular cartilage using driven equilibrium

The high incidence of osteoarthritis and the recent advent of several new surgical and non-surgical treatment approaches have motivated the development of quantitative techniques to assess cartilage loss. Although magnetic resonance (MR) imaging is the most accurate non-invasive diagnostic modality for evaluating articular cartilage, improvements in spatial resolution, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) would be valuable. Cartilage presents an imaging challenge due to its short T2 relaxation time and its low water content compared with surrounding materials. Current methods sacrifice cartilage signal brightness for contrast between cartilage and surrounding tissue such as bone, bone marrow, and joint fluid. A new technique for imaging articular cartilage uses driven equilibrium Fourier transform (DEFT), a method of enhancing signal strength without waiting for full T1 recovery. Compared with other methods, DEFT imaging provides a good combination of bright cartilage and high contrast between cartilage and surrounding tissue. Both theoretical predictions and images show that DEFT is a valuable method for imaging articular cartilage when compared with spoiled gradient-recalled acquisition in the steady state (SPGR) or fast spin echo (FSE). The cartilage SNR for DEFT is as high as that of either FSE or SPGR, while the cartilage-synovial fluid CNR of DEFT is as much as four times greater than that of FSE or SPGR. Implemented as a three-dimensional sequence, DEFT can achieve coverage comparable to that of other sequences in a similar scan time. Magn Reson Med 42:695–703, 1999. © 1999 Wiley-Liss, Inc.
Intergenerational transfers of headships over the life course in an Eastern European peasant community, 1782–1850

Research on intergenerational transfers of valued goods has focused mostly on historical western Europe and its propertied peasantry. This article analyzes the population of an estate (Pinkenhof) in the Russian Baltic province of Livland—one of the lands of the so-called “second serfdom”—during the nineteenth century, before and after the emancipation of serfs. Here peasants did not own land; the most valued good that peasant families had to bequeath was an office—the headship of a farmstead. Emancipation brought a substantial decrease of kin as successors to headships, and a corresponding increase in the proportion of headships that went to non-kin from the same farmstead. A possible explanation for this phenomenon lies in the new attitudes of the post-emancipation period, as estate owners and peasant families gave greater value te demonstrated competence than to kinship in choosing candidates for headships.
Odonata origins, biogeography, and diversification in an Eastern North American hotspot: multiple pathways to high temperate forest insect diversity

We assessed the origins and historical biogeography of a rich regional odonate fauna in New York State (NYS), Northeastern United States. We computed North American (NA) range centres and NYS range margins and reviewed the taxonomic literature to provide a useful phylogenetic framework for the fauna. We analysed results from a newly completed Odonata atlas using generalised linear anova models to assess the effects of species' origins and zoogeographic affinities on relative frequency and extinction risk metrics. Phylogenetic reconstruction based on taxonomic nomenclature revealed different patterns of diversification. Zygoptera in NYS is mainly of neotropical origin ˜ 60 Ma displaying a pattern of tropical conservatism, but with a burst recent of Plio–Pleistocene speciation in certain groups. Alternatively, Anisoptera contains crown group endemic taxa and other very old lineages from the Mesozoic era before the breakup of Pangaea, highlighting the evolutionary significance of the Appalachian Mountains as an important global centre of temperate forest freshwater diversity. These high regional levels of odonate diversity have been brought about by at least three different mechanisms: dependence on forests, predominance of non-ecological speciation mechanisms, and niche conservatism across hundreds of millions of generations. NYS lies at a crossroads of both ancient and more recent Odonata evolution comprising separate boreal, temperate, and tropical faunas. Those species encountered less frequently and having higher overall extinction risk metrics generally tended to be the boreal species on the rear edge of their range, a widespread phenomenon for the insects of many regions generally attributed to ongoing climate change.
Why CHI fragmented

I have been active in SIGCHI since 1983, serving on the Executive Committee and many conference and program committees. After editing ACM TOCHI for six years, I explored the history of CHI and related fields. The "conference-centered" model unique to U.S. computer science, wherein little published research reaches journals, and uncertainty regarding HCI's academic niche have created an unusual situation. I propose some paths forward.
Efficient estimation of sensory thresholds

Laboratory computers permit detection and discrimination thresholds to be measured rapidly, efficiently, and accurately. In this paper, the general natures of psychometric functions and of thresholds are reviewed, and various methods for estimating sensory thresholds are summarized. The most efficient method, in principle, using maximum-likelihood threshold estimations, is examined in detail. Four techniques are discussed that minimize the reported problems found with the maximum-likelihood method. A package of FORTRAN subroutines, ML-TEST, which implements the maximum-likelihood method, is described. These subroutines are available on request from the author.
Changing software philosophy for ACIS operations as Chandra ages

The Chandra X-Ray Observatory is about to start its 10th year of operations. Over the time of the mission, the Science Operations Team, ACIS (Advanced CCD Imaging Spectrometer) Operations group, has participated in spacecraft command load reviews. These reviews ensure the spacecraft commanding is safe for the instrument and the ACIS configuration matches the planned observation. The effectiveness of spacecraft command load reviews for ACIS depends on the ability to adapt the software as operations change in response to the aging of the spacecraft. We have recently rewritten this software to start incorporating other spacecraft subsystems, including maneuvers and hardware commanding, to ensure the safety of ACIS. In addition, operational changes that optimize the science return of the spacecraft have created new constraints on commanding. This paper discusses the reorganization of the code and the multiple changes to the philosophy of the code. The result is stronger, more flexible software that will continue to assist us in protecting ACIS throughout the Chandra mission.
Methyl green. III. Reaction with desoxyribonucleic acid, stoichiometry, and behavior of the reaction product.

1. Methyl green ("ethyl green") C. I. Number 685 was examined and found to behave identically with methyl green C. I. Number 684 (no longer available) in respect to molar extinction coefficient, effect of combination with polymerized DNA, failure to react with depolymerized DNA, and effect of pH. 2. The mass law permits the calculation of P/dye. This is found to be 13 P/dye. The same value is obtained when an excess of methyl green is caused to fade by adjusting the pH to 7.5. 3. The compound formed by methyl green with DNA has the same maximum absorption at 642.5 to 645 mµ in the pH range 3.5–7.8, whereas the free dye fades markedly above pH 5.0.
The Gene Encoding the Mitogen-responsive Phosphoprotein Dab2 Is Differentially Regulated by GATA-6 and GATA-4 in the Visceral Endoderm

Gene targeting studies have demonstrated that the zinc finger transcription factor GATA-6 lies upstream in a transcriptional cascade that controls differentiation of the visceral endoderm. To understand the function of GATA-6 in the visceral endoderm and to identify genes regulated by GATA-6 in this tissue, subtractive hybridization was performed using template cDNAs derived from differentiated wild-type embryonic stem (ES) cells and GATA-6(-/-) ES cells, respectively. These analyses revealed that the gene encoding Dab2, a mitogen-responsive phosphoprotein, is differentially expressed in wild-type and GATA-6-deficient ES cells. Consistent with these findings, Dab2 is expressed in the visceral endoderm of wild-type embryos but not in the visceral endoderm of GATA-6-deficient embryos. Cotransfection experiments demonstrate that the human Dab2 promoter can be transactivated by forced expression of GATA-6 in NIH-3T3 cells. In contrast, forced expression of GATA-4 does not transactivate the human Dab2 promoter and Dab2 is expressed in the visceral endoderm of GATA-4 null embryos. Surprisingly, the specificity of GATA-6-induced transactivation of the Dab2 promoter is not mediated through its zinc finger DNA-binding domain. Taken together, these data demonstrate that the mitogen-responsive phosphoprotein Dab2 is a downstream target of GATA-6 in the visceral endoderm. Moreover, these data demonstrate that molecular mechanisms have evolved that direct, and distinguish, the functional specificity of GATA family members when they are developmentally coexpressed.
Complex systems study as biology

If we pay serious and conscientious attention to the connotation of the word "complexity", study of complex systems must basically be biology. Basic questions are raised from this point of view.
An examination of substitutes for leadership within a levels-of-analysis framework

Abstract The goal of this study was to examine the relative impact of individual-level and group-level effects of several leader behaviors and substitutes for leadership on employee attitudes, role perceptions, and “inrole” and “extra-role” performance. Data were collected from 1235 employees from 265 work groups across a variety of organizational settings. The presence of group-level effects was tested with ANOVA, and clear evidence of both group-level and individual-level differences was found. Multiple regression procedures, which controlled for all of the leader behaviors and the substitutes for leadership at both the individual and group levels of analysis, generally showed that: (1) the combination of leader behaviors and substitutes for leadership accounted for substantial amounts of variance in the subordinate's attitudes, role perceptions, and performance; (2) the leadership substitutes accounted for more variance in the subordinate criterion variables than did the leader behaviors; and (3) although the effects of within-group variation in leader behaviors and substitutes for leadership were substantially stronger than between-groups variation on subordinates' attitudes and role perceptions, both within-group and between-groups variation in the leader behaviors and leadership substitutes had important effects on subordinates' inrole and extra-role performance. The implications of these findings are discussed.
Spatial and temporal distribution of axonal degeneration in the primary optic system of the cat

Abstract The spatial and temporal distribution of optic fiber degeneration was studied with three selective silver methods in cats which sustained unilateral optic nerve transection 2 days to 15 mo before death. At the second postoperative day, only traumatic disintegration was discernible. Starting with the fourth day, axonal degradation appeared in central portions of optic pathways and centers. Degeneration spread throughout the pathways at the seventh day and reached a plateau in 9–10 days postoperatively. No overt changes were noted in the subsequent 2 mo. From the third month on there was a gradual and even reduction in the amount of impregnated degeneration products, except for that in the dorsal lateral geniculate and superior colliculus which vanished sooner. With deterioration times of 6 mo or longer, only occasional scattered debris could be detected. There was no significant “late degeneration” to suggest the presence of centrifugal (efferent or retinopetal) optic fibers.