cssi/SciSciGPT-SciSciNet huggingface dataset:
What Makes Some Problems Really Hard: Explorations in the Problem Space of Difficulty

Abstract This paper identifies two sources, one larger, one smaller, of the great difficulty encountered by subjects solving the Chinese Ring puzzle. Almost none of our subjects were able to solve the puzzle within 2 h unless they were given a demonstration of how to move, and even with that help only half of the subjects obtained solutions. Discovering how to make moves, rather than other features of the problem search space, was the source of its inordinate difficulty. Evidence for this comes from isomorphs that were designed to “digitize” the moves, which in the original version have analog qualities. These digital isomorphs were solvable by almost all subjects, with average solution times of 10 to 25 min, depending on isomorph type. The sense in which these altered problems were isomorphic to the original ones is explored. The isomorphism is defined in terms of an external search space consisting of a graph of nodes which represent states of knowledge, and links between those states which represent legal moves. Subjects' representations of the more difficult problems evolve toward isomorphism as they discover what constitutes a move. The digitized problems still required considerable effort for their solution. The difficulty of these problems in digital form is particularly surprising, given that the problem search space is linear: there is no branching. Hence, size of search space (exponential explosion) was not the source of difficulty here. The linearity of the search space did not prevent the subjects from making a large number of moves in reaching a solution. The average number of moves ranged from 150 to 450 for different isomorphs. In addition, the subjects' move behavior was often dichotomous, consisting of a very large number of nonprogressive, often error-prone moves, followed by a very rapid, often error-free movement to the goal. In our examination of the sources of difficulty for this problem, we also studied the transfer of skill between different isomorphs. The investigation of transfer-of-training showed that problem-representational features such as move-operator compatibility, move difficulty, and the presence or absence of move legality cues determined the amount of transfer.
High-performance liquid chromatographic analysis of wheat flour lipids using an evaporative light scattering detector

Abstract A high-performance liquid chromatographic method which utilized an evaporative light scattering detector for separation of starch and non-starch lipids of unbleached soft red winter wheat flour is described. Separation of the major starch and non-starch lipids was achieved in 60 min using a Lichrosorb Si-60 silica cartridge system and ternary gradient system. The evaporative light scattering detector gave a flat stable baseline, reproducible results and also eliminated the “solvent fronts” in which peaks of interest would have co- eluted. The technique was found useful in identifying the lipids and their relative mass percentages that were present in the flour.
SU-FF-T-208: Modeling the Headscatter Off-Axis in Megavoltage Photon Beams

Purpose: To accurately model off‐axis headscatter from a linear accelerator at off‐axis positions using a parameterized, two‐component model. An improved model is now proposed to model headscatter outside beam collimation.Method and Materials: We define the head‐scatter off‐axis ratio, HOA, as the ratio of the kerma due to head‐scatter photons at the off‐axis position x to the kerma from direct primary photons on the central axis. “Direct primary” are those photons that come from the source without interactions in the intervening structures. We measured HOA along the X jaw direction from the central axis to a distance of 25 cm from the field edge for various collimator settings. We fit the measured HOA using an improved two‐component model. The first component is a Gaussian source projected on a plane below the x‐ray source, representing the headscatter from the flattening filter and the primary collimator. Compared to an earlier model [1], this model models the second component for photonsscattered in the secondary (variable) collimators using a linear edge kernel integrated over the four collimator jaws. Headscatter off‐axis outside beam collimation is examined more extensively with this study. Results: The two‐component model can be fit to data obtained from a variety of fields with a mean (maximum) local relative error of 10% (35)%. The region outside the penumbra region is modeled primarily by the collimator component. Conclusion: A two‐component model in which the headscatter from the flattening filter and the collimators are modeled separately can accurately predict HOA values for arbitrary collimator settings.
CRYSTAL-STRUCTURE OF THE PHOSPHOTYROSINE RECOGNITION DOMAIN SH2 OF V-SRC COMPLEXED WITH TYROSINE-PHOSPHORYLATED PEPTIDES

Three-dimensional structures of complexes of the SH2 domain of the v-src oncogene product with two phosphotyrosyl peptides have been determined by X-ray crystallography at resolutions of 1.5 and 2.0 A, respectively. A central antiparallel β-sheet in the structure is flanked by two α-helices, with peptide binding mediated by the sheet, intervening loops and one of the helices. The specific recognition of phosphotyrosine involves amino–aromatic interactions between lysine and arginine side chains and the ring system in addition to hydrogen-bonding interactions with the phosphate.
Student Unrest in the Nineteenth Century: A Sociological Case Study

This paper examines student unrest at a single university in the late nineteenth century as a case study of the general student rebellion common in land-grant schools during that period. A conceptual framework exploring the relationship between an emerging student culture, traditional educational philosophy, and contemporary trends of economic and demographic change is used to interpret these historical data. Students actively sought university experiences that would facilitate movement into occupational roles expanding as a result of these trends. The unwillingness of the university to facilitate this movement resulted in two student rebellions, which in turn forced the university into accepting a previously rejected student culture. These case study data suggest that rural populations during the late nineteenth century used land-grant colleges and universities as avenues for upward mobility, often against the wishes of campus administrators. Comparisons are made between student unrest during this period and the 1960s.
Actuator requirements for an active suspension to prevent two-wheel lift-off in a severe manoeuvre

The force requirements and control laws for an actuator forming a part of an active suspension are derived using the framework of optimal control theory. Prevention of two wheel lift-off during a severe fish-hook manoeuvre is identified as the critical performance requirement for the actuator. The equations of motion of the vehicle equipped with the active system are used to formulate an optimal control problem with constraints on the suspension motion and various design considerations taken as objective functions. Solution of the optimal control problem yields time-dependent active suspension forces to be applied to prevent two-wheel lift-off and thus improve its road-holding capability. The influence of actuation modes, force constraints, actuator response characteristics, etc. on the nature of active force variation is studied and system level control strategies are developed.
The Effect of Intake Valve Deactivation on Lean Stratified Charge Combustion at an Idling Condition of a Spark Ignition Direct Injection Engine

A combined experimental and analytical study was carried out to understand the improvement in combustion performance of a 4-valve SIDI wall-guided engine operating at lean, stratified idle with enhanced in-cylinder charge motion by deactivating one of the two intake valves. A fully warmed-up engine was operated at low speed, light load by injecting the fuel from a pressure-swirl injector during the compression stroke to produce a stratified fuel cloud surrounding the spark plug at the time of ignition. Steady state flow-bench measurements and CFD calculations showed that valve deactivation primarily increased the in-cylinder swirl intensity as compared with opening both intake valves. Engine dynamometer measurements showed an increase in charge motion led to improved combustion stability, increased combustion efficiency, lower fuel consumption, and higher dilution tolerance. A CFD study was conducted using in-house models of spray and combustion to simulate the engine operating with and without valve deactivation. The computations demonstrated that the improved combustion was primarily driven by higher laminar flame speeds through enhanced mixing of internal residual gases, better containment of the fuel cloud within the piston bowl, and higher post-flame diffusion burn rates during the initial, main, and late stages of the combustion process, respectively.Copyright © 2011 by General Motors
Histone acetylation in synchronized mammalian cell cultures.

Abstract Synchronized cultures of mammalian cells were labeled with [ 3 H]acetate. Incorporation of labeled acetate into histone fractions was followed through the cell cycle from late G 1 , through S and G 2 , into early M. The acetate contents of histone fractions F2a, F2b and F3 rose rapidly to a maximum in late S, coincident with the termination of DNA synthesis, and declined rapidly thereafter. The acetate content of histone fraction F1 rose to a maximum in mid-S, coincident with maximal DNA synthesis, and decreased rapidly thereafter. Fractions F1 and F2b lost the majority of their incorporated acetate, while fractions F2a and F3 retained approximately half their incorporated acetate. Evidence is presented for differential acetylation of histone fractions, for a temporal coupling of histone biosynthesis and acetylation and for a differential turnover of histone fraction acetyl groups.
Changes in the chemical and dynamic properties of cardiac troponin T cause discrete cardiomyopathies in transgenic mice.

Cardiac troponin T (cTnT) is a central component of the regulatory thin filament. Mutations in cTnT have been linked to severe forms of familial hypertrophic cardiomyopathy. A mutational “hotspot” that leads to distinct clinical phenotypes has been identified at codon 92. Although the basic functional and structural roles of cTnT in modulating contractility are relatively well understood, the mechanisms that link point mutations in cTnT to the development of this complex cardiomyopathy are unknown. To address this question, we have taken a highly interdisciplinary approach by first determining the effects of the residue 92 mutations on the molecular flexibility and stability of cTnT by means of molecular dynamics simulations. To test whether the predicted alterations in thin filament structure could lead to distinct cardiomyopathies in vivo, we developed transgenic mouse models expressing either the Arg-92-Trp or Arg-92-Leu cTnT proteins in the heart. Characterization of these models at the cellular and whole-heart levels has revealed mutation-specific early alterations in transcriptional activation that result in distinct pathways of ventricular remodeling and contractile performance. Thus, our computational and experimental results show that changes in thin filament structure caused by single amino acid substitutions lead to differences in the biophysical properties of cTnT and alter disease pathogenesis.
Autophagy: in sickness and in health

The degradation of intracellular components in lysosomes (autophagy) has recaptured the attention of cell biologists in recent years. The main reason for this renewed interest is the dissection of the molecular machinery that participates in this process, because the identification of new intracellular elements involved in autophagy has provided new tools to trace, quantify and manipulate autophagy in a growing number of organisms. As a result, a better understanding of the physiological roles of autophagy, the consequences of its malfunctioning and its participation in different pathological processes has emerged. This article reviews our current knowledge of the role of autophagy in disease and the efforts to reconcile its proposed dual function as both a cell protector and a cell killer.
Mapping a cardiomyopathy locus to chromosome 3p22-p25

Dilated cardiomyopathy (DCM) is a common disorder characterized by cardiac dilation and reduced systolic function. To identify a cardiomyopathy gene, we studied a family with DCM associated with sinus node dysfunction, supraventricular tachyarrhythmias, conduction delay, and stroke. A general linkage approach was used to localize the disease gene in this family. Linkage to D3S2303 was identified with a two-point lod score of 6.09 at a recombination fraction of 0.00. Haplotype analyses mapped this locus to a 30 cM region of chromosome 3p22-p25, excluding candidate genes encoding a G-protein (GNAI2), calcium channel (CACNL1A2), sodium channel (SCN5A), and inositol triphosphate receptor (ITPR1). These data indicate that a gene causing DCM associated with rhythm and conduction abnormalities is located on chromosome 3p, and represent the first step toward disease gene identification.
Normal Anatomic Variants on Transthoracic Echocardiogram

Apart from their existence as medical curiosities, anatomic variants also double as diagnostic dilemmas. In the heart, more than in any other location in the body, misinterpretation of normal anatomic variants as pathologic entities can have a profound impact on treatment decisions and clinical consequences. Echocardiography is an easily accessible tool these days and is used routinely in most cardiac evaluations. Thus it becomes imperative for the echocardiographer to be cognizant of normal anatomic variants. Furthermore, echocardiographic findings should always be evaluated in their proper clinical context and diagnoses should never be entertained in a clinical vacuum. The literature is replete with numerous case reports and vignettes on these fascinating structures but is lacking in a formal review of normal anatomic variants. In this article, we have attempted a systemic review of normal variants, their embryologic origins, echocardiographic characteristics, and common pitfalls encountered in their evaluation.
A comment on glenn Firebaugh’s “population density and fertility”

Firebaugh has attempted to test an interesting, if counterintuitive, theory. I have argued that his empirical model is incompletely specified, and that one should reserve judgement on his hypothesis until a better means of testing it can be developed. In particular, the use of ratio variables and pooled data create substantial statistical problems.f The simultaneous responses of the CBR and village population size to outside-of-model variation yield an inflated estimate of the effect of population density on fertility.
Peptides as central regulators of feeding

During the past decade there has been an increased awareness of the role peptides play as neuromodulators. In this article we review the available data on peptides as central regulators of food ingestion. We stress the possible problems of non-specific effects. We stress that whereas many peptides decrease feeding after central injection, only two families of peptides have been shown to increase feeding after central injection. These are the opioid family and the pancreatic polypeptide-neuropeptide Y family. The putative role of corticotropin releasing factor as the mediator of norepinephrine and serotonin effects on feeding is discussed.
Assessing Interpersonal Trauma in Older Adult Women

Interpersonal traumatic experiences (childhood abuse, sexual assault, and intimate partner violence) are common in older adult women and associated with negative short-term and long-term outcomes. Thus, assessing trauma symptoms is essential to providing adequate services. This article explores challenges of measuring trauma in older women, describes the Posttraumatic Diagnostic Scale (Foa, 1995), and evaluates the appropriateness of this instrument using data from a current study of older adult women. Symptom severity scores did not consistently reflect the experiences of the sample. Eschewing a clinical interview to assess the impact of interpersonal trauma in older adult women may be a mistake.
Characterization of the phase-contrast radiography edge-enhancement effect in a cabinet x-ray system.

The purpose of this study was to demonstrate that a commercially available cabinet x-ray system is capable of phase-contrast radiography (PC-R) and to evaluate the effect of different system parameters on the degree of edge enhancement. An acrylic plastic edge phantom was imaged at different tube potentials (25–60 kV) and in different geometries (variable object-to-detector distances, R2, at a constant source-to-detector distance, R1 + R2). In addition, the effect of noise on the perceived edge enhancement was studied as a function of exposure time. Our results show that a modest degree of phase contrast can be achieved in an unmodified cabinet x-ray system. In addition, the particular system evaluated allowed low-noise PC-R images to be obtained with short (6 s or less) exposures. These results suggest that with appropriate geometric choices PC-R is already available to a wide range of research scientists for use in both small-animal and human-specimen experiments.
Acquired Leukonychia Totalis

This 72-year-old woman with diabetes mellitus reported dyspnea, orthopnea, and a progressive whitening of her fingernails.
Analysis of prehospital pediatric and adult intubation.

Abstract Purpose: Pediatric airway control, including endotracheal intubation (ETI), presents a clinical challenge in the prehospital setting. Endotracheal intubation is recommended for serious head injury (Glasgow Coma Scale score ⪯ 8). We evaluated the frequency of ETI in pediatric and adult patients with GCS ⪯8 in the field, subsequently transported by a hospital-based, helicopter emergency medical service (HHEMS). Methods: A retrospective, descriptive study of pediatric patients (5514 years) and adult patients with GCS 58 transported by HHEMS from January 1988 through March 1994 was conducted. Significance was determined by chi-square analysis. Results: Inclusion criteria were met by 63 (15%) pediatric patients and 353 (85%) adults. Of the pediatric patients, 38 (60%) were intubated endotracheally; mean age was 7; mean injury severity score (ISS) was 28. Of adults, 267 (76%) were intubated endotracheally; mean age was 35; mean ISS was 33. A 16-percentagepoint difference in frequency of successful ETI between groups was found to be significant (p 5⪯0.01). Of 25 nonintubated pediatric (PED) patients, unsuccessful attempts were made on 20 (80%); 14 of 25 (56%) had significant head injuries evident on computerized tomography (CT) scan. Of 86 nonintubated adults, unsuccessful attempts were made on 29 (34%); 61 (71 %) had significant head injuries. Conclusions: Pediatric coma patients were not intubated with the same frequency as adults. This discrepancy between groups was secondary to a higher failure rate in the pediatric group. Intubation was attempted in 92% of pediatric patients versus 84% of the adults. Unsuccessful intubation attempts in the pediatric group, 20 of 58 (34%), were compared with 29 of 296 (9.8%) in the adult group. Difficulty in pediatric airway control may require an increased level of training and experience.
Comparison of quasi-static and dynamic wind tunnel measurements on simplified tractor-trailer models

Abstract The results from a series of wind tunnel experiments are presented, intended to measure dynamic forces and moments on simplified commercial vehicle type models rotating about their vertical centre line axis in smooth, uniform flow. These results are compared with quasi-static measurements on the same models over a range of fixed yaw angles (the conventional technique for wind tunnel test on this type of vehicle) in order to assess the significance of attempting to simulate the essentially dynamic nature of the full scale flowfield in a wind tunnel. It is shown that the magnitude of drag and yawing moment coefficients do not change significantly even at rotational rates as high as 64° s −1 . However the dynamic coefficient versus yaw angle curves appear displaced, relative to the yaw angle axis, compared to the static data. The magnitude and sign of this “phase shift” are seen to be dependent on both yaw rate and model geometry and are evident at rotational rates as low as 0.25° s −1 .
Circulant preconditioners for Toeplitz-block matrices

We propose two block preconditioners for Toeplitz-block matrices (i.e. each block is Toeplitz), intended to be used in conjunction with conjugate gradient methods. These preconditioners employ and extend existing circulant preconditioners for point Toeplitz matrices. The two preconditioners differ in whether the point circulant approximation is used once or twice, and also in the cost per step. We discuss efficient implementation of these two preconditioners, as well as some basic theoretical properties (such as preservation of symmetry and positive definiteness). We report results of numerical experiments, including an example from active noise control, to compare their performance.
A spiral-doublet scanning array

An array of eight spiral doublets, each doublet consisting of a pair of equally-excited two-wire spirals in the same plane and wound in opposite senses, has been used to scan a beam of horizontal polarization over a \pm 40\deg range simply by rotations of the spiral doublets. The combination of a microstrip ring network and twin lead provided a balanced feed for each spiral in the array. Sidelobe levels were those predicted (25 db) for the broadside pattern and-at the test frequency of 1430 Mc-were, in general, below 19 db over the 80\deg scan. A novel microstrip feed harness provided isolation between the doublets and served to absorb most circulating currents. This printed circuit feedboard consisted of judiciously-grouped microstrip ring networks and provided the desired feeding coefficients to within \pm0.1 db. An application of the array for tracking purposes is also described.
Is counterion delocalization responsible for collapse in RNA folding

Although energetic and phylogenetic methods have been very successful for prediction of nucleic acid secondary structures, arrangement of these secondary structure elements into tertiary structure has remained a difficult problem. Here we explore the packing arrangements of DNA, RNA, and DNA/RNA hybrid molecules in crystals. In the conventional view, the highly charged double helix will be pushed toward isolation by favorable solvation effects; interactions with other like-charged stacks would be strongly disfavored. Contrary to this expectation, we find that most of the cases analyzed (∼80%) exhibit specific, preferential packing between elements of secondary structure, which falls into three categories: (i) interlocking of major grooves of two helices, (ii) side-by-side parallel packing of helices, and (iii) placement of the ribose−phosphate backbone ridge of one helix into the major groove of another. The preponderance of parallel packing motifs is especially surprising. This category is expected to b...
CAS Applied in a Functional Perspective College Algebra Curriculum

Summary Act in Algebra(ACT) is a functional perspective curriculum for college algebra that focuses on the use of realistic applications to motivate the acquisition of mathematical concepts through active student explorations. A computer algebra system (CAS) is used as an open-ended tool in the exploration of mathematics and the modeling of data. The goal of ACT is to improve student cognition, metacognition, and affect with respect to college algebra. A series of studies was conducted from the spring of 1994 to the spring of 1999 to determine the effects of the CAS in a functional perspective curriculum. This article provides an overview of the findings of those studies and discusses the implications of these findings for the teaching and learning of algebra.
A Novel Member of the Netrin Family, β-Netrin, Shares Homology with the β Chain of Laminin

The netrins are a family of laminin-related molecules. Here, we characterize a new member of the family, β-netrin. β-Netrin is homologous to the NH2 terminus of laminin chain short arms; it contains a laminin-like domain VI and 3.5 laminin EGF repeats and a netrin C domain. Unlike other netrins, this new netrin is more related to the laminin β chains, thus, its name β-netrin. An initial analysis of the tissue distribution revealed that kidney, heart, ovary, retina, and the olfactory bulb were tissues of high expression. We have expressed the molecule in a eukaryotic cell expression system and made antibodies to the expressed product. Both in situ hybridization and immunohistochemistry were used to describe the cellular source of β-netrin and where β-netrin is deposited. β-Netrin is a basement membrane component; it is present in the basement membranes of the vasculature, kidney, and ovaries. In addition, β-netrin is expressed in a limited set of fiber tracts within the brain, including the lateral olfactory tract and the vomeronasal nerve. Functional studies were performed and show that β-netrin promotes neurite elongation from olfactory bulb explants. Together, these data suggest that β-netrin is important in neural, kidney, and vascular development.
Motion planning for urban driving using RRT

This paper provides a detailed analysis of the motion planning subsystem for the MIT DARPA Urban Challenge vehicle. The approach is based on the Rapidly-exploring Random Trees (RRT) algorithm. The purpose of this paper is to present the numerous extensions made to the standard RRT algorithm that enable the on-line use of RRT on robotic vehicles with complex, unstable dynamics and significant drift, while preserving safety in the face of uncertainty and limited sensing. The paper includes numerous simulation and race results that clearly demonstrate the effectiveness of the planning system.
PER3 polymorphism predicts cumulative sleep homeostatic but not neurobehavioral changes to chronic partial sleep deprivation.

Background: The variable number tandem repeat (VNTR) polymorphism 5-repeat allele of the circadian gene PERIOD3 (PER3 5/5 ) has been associated with cognitive decline at a specific circadian phase in response to a night of total sleep deprivation (TSD), relative to the 4-repeat allele (PER3 4/4 ). PER3 5/5 has also been related to higher sleep homeostasis, which is thought to underlie this cognitive vulnerability. To date, no study has used a candidate gene approach to investigate the response to chronic partial sleep deprivation (PSD), a condition distinct from TSD and one commonly experienced by millions of people on a daily and persistent basis. We evaluated whether the PER3 VNTR polymorphism contributed to cumulative neurobehavioral deficits and sleep homeostatic responses during PSD. Methodology/Principal Findings: PER3 5/5 (n=14), PER3 4/5 (n=63) and PER3 4/4 (n=52) healthy adults (aged 22–45 y) demonstrated large, but equivalent cumulative decreases in cognitive performance and physiological alertness, and cumulative increases in sleepiness across 5 nights of sleep restricted to 4 h per night. Such effects were accompanied by increasing daily inter-subject variability in all groups. The PER3 genotypes did not differ significantly at baseline in habitual sleep, physiological sleep structure, circadian phase, physiological sleepiness, cognitive performance, or subjective sleepiness, although during PSD, PER3 5/5 subjects had slightly but reliably elevated sleep homeostatic pressure as measured physiologically by EEG slow-wave energy in non-rapid eye movement sleep compared with PER3 4/4 subjects. PER3 genotypic and allelic frequencies did not differ significantly between Caucasians and African Americans. Conclusions/Significance: The PER3 VNTR polymorphism was not associated with individual differences in neurobehavioral responses to PSD, although it was related to one marker of sleep homoeostatic response during PSD. The comparability of PER3 genotypes at baseline and their equivalent inter-individual vulnerability to sleep restriction indicate that PER3 does not contribute to the neurobehavioral effects of chronic sleep loss.
PET of EGFR Antibody Distribution in Head and Neck Squamous Cell Carcinoma Models

Epidermal growth factor receptor (EGFR) is a well-characterized protooncogene that has been shown to promote tumor progression in solid cancers. Clinical results for EGFR targeting with specific monoclonal antibodies (mAbs) such as cetuximab and panitumumab are promising; however, most studies indicate that only a subgroup of patients receiving the mAbs benefit from the immunotherapy, independent of EGFR expression level. To understand the in vivo kinetics of antibody delivery and localization, we performed small-animal PET studies with 64 Cu-labeled panitumumab in xenografts derived from 3 cell lines of human head and neck squamous cell carcinoma (HNSCC). Methods: Nude mice bearing HNSCC tumors with different levels of EGFR expression were imaged with
Safety of ERCP during pregnancy.

Abstract Objectives There are few data in the literature regarding the indications, therapy, and safety of endoscopic management of pancreatico-biliary disorders during pregnancy. We report the largest single center experience with ERCP in pregnancy. Methods We reviewed 15 patients that underwent ERCP during pregnancy. In all patients, the pelvis was lead-shielded and the fetus was monitored by an obstetrician. Fluoroscopy was minimized and hard copy radiographs taken only when essential. Results The mean patient age was 28.9 yr (15–36 yr). The mean duration of gestation was 25 wk (12–33 wk); one patient was in the first, five in the second, and nine in the third trimester. The indications were gallstone pancreatitis (n = 6), choledocholithiasis on ultrasound (n = 5), elevated liver enzymes and a dilated bile duct on ultrasound (n = 2), abdominal pain and gallstones (n = 1), and chronic pancreatitis (n = 1). ERCP findings were bile duct stones (n = 6), patulous papilla (n = 1), bile duct debris (n = 1), normal bile duct and gallstones or gallbladder sludge (n = 3), dilated bile duct and gallstones (n = 1), normal bile duct and no gallstones (n = 2), and chronic pancreatitis (n = 1). Six patients underwent sphincterotomies and one a biliary stent insertion. One sphincterotomy was complicated by mild pancreatitis. All infants delivered to date have had Apgar-scores >8, and continuing pregnancies are uneventful. Mean fluorosocopy time was 3.2 min (SD ± 1.8). An estimated fetal radiation exposure was 310 mrad (SD ± 164) which is substantially below the accepted teratogenic dose. Conclusions ERCP in pregnancy seems to be safe for both mother and fetus; however, it should be restricted to therapeutic indications with additional intraprocedure safety measures.
Evolved radial basis function networks for identification and control of dynamical systems

This paper presents a new approach to the identification and control of dynamical systems by means of evolved radial basis function neural networks (ERBFNs). Traditionally, radial basis function networks (RBFNs) parameters which are used for identification and control are fixed beforehand by a trial-and-error process. This process consists of finding structural and training parameters. Once these parameters are fixed the only parameters that remain to be determined are network weights. In general, the weights are adjusted using a gradient approach so that network output asymptotically follow the plant output. In this paper a new approach to the selection of structural and training parameters is introduced. A hybrid system is proposed which uses an evolutionary algorithm to select optimum structural parameters and uses the LMS algorithm to adjust network weights. In this context, RBFN parameters such as basis function centers, widths and training parameters are chosen at random and adjusted by an evolutionary algorithm, throughout the identification and control process. Experimental results show that the system is able to effectively identify and control dynamical systems.
Rational Covariance Functions for Nonstationary Random Fields

This correspondence propose rational-type covariance functions for nonstationary Gaussian stochastic processes or random fields, which are rational functions of given variograms, typically have long range dependence, and include some stationary covariance functions as special cases.
Antecedents of Physical Activity Among Family Caregivers

The authors examined exercise behaviors among family caregivers and the degree to which aspects of the caregiving role influenced exercise behaviors. Understanding factors associated with caregiver physical activity provides practitioners the means to design and tailor interventions to be effective for caregivers. Caregivers (N = 208) participating in a self-care intervention to promote caregiving skills were surveyed at baseline, prior to training. Measures included caregiver characteristics, care recipient characteristics, attitudes and intentions toward exercise, and levels of physical activity. Mental health variables and self-efficacy for exercise were significantly related to exercise levels in bivariate analyses. Regression analyses revealed that caregiver and care recipient characteristics accounted for a small percentage of the variance in exercise behavior. Caregiver vitality and self-efficacy for exercise were key variables most significantly related to exercise behaviors. Findings suggest that...
Changes in Antihypertensive Prescribing During US Outpatient Visits for Uncomplicated Hypertension Between 1993 and 2004

Monitoring national patterns of antihypertensive drug therapy is essential to assessing adherence to treatment guidelines and the impact of major scientific publications on physician prescribing. We analyzed data from 2 US National Ambulatory Care Surveys to examine trends between 1993 and 2004 in the prescription of antihypertensive drug classes for uncomplicated hypertension and the association between thiazide and β-blocker prescribing and physician and patient characteristics. Diuretic prescriptions remained level through 2001 (39%; 95% CI: 34% to 44%) but increased to 53% (48% to 58%) in 2003, largely because of a 72% increase in thiazide prescriptions in the first quarter of 2003 (50%; 95% CI: 40% to 59%). However, these increases did not sustain in 2004. β-Blocker prescriptions increased modestly from 1993 (24%; 95% CI: 19% to 29%) to 2004 (33%; 95% CI: 28% to 39%). Prescription of calcium channel blockers and angiotensin-converting enzyme inhibitors declined significantly following the sixth Joint National Committee report, but both subsequently rebounded to prereport levels. Prescription of angiotensin II receptor blockers increased continuously from 1% in 1995 to 23% by 2004. Polytherapy prescriptions, particularly those involving ≥3 drug classes, became increasingly prevalent, accounting for 60% of antihypertensive drug visits by 2004. Prescriptions of thiazides and β-blockers were both more likely in 1998–2004 (versus 1993–1997). Blacks, women, and hospital outpatients were more likely to receive thiazides. Also, cardiologists were more likely to prescribe β-blockers. Evidence-based guidelines for antihypertensive drug therapy do impact physician prescribing, but the impact seems to be short lived. Future interventions are imperative for promoting long-term adherence to published guidelines.
An historical analysis of engineering college research and degree programs as dynamic systems

An analysis is made to illuminate and interpret the recent history of engineering education. The production of engineering degrees and research is modeled as a dynamic process using parameters derived for that purpose. The dominant fact in the production of bachelors degrees is the damped oscillatory growth which characterized the two decades after World War II. Short-term fluctuations exist, but over the long term the growth rate matches U.S. population growth rate. Graduate degree production increased at a constant 12 percent per year between 1956 and 1968, resulting in the ratio of graduate degrees to B.S. degrees increasing from 1:6 to the current 1:2. Methods are developed to classify colleges of engineering according to their dominant characteristic as graduate or undergraduate institutions. Growth in Ph.D. production is shown to have been influenced by a "geographical potential" as well as other factors. Application is made to a method for planning graduate research centers in developing countries. Cost effectiveness in graduate research is shown to correlate with size. The largest colleges are shown to have maintained their productivity while smaller ones declined during periods of decreasing national production. Methods for critical comparison of colleges, departments, and even professors, are discussed and illustrated.
The scanning DMA transfer function

The scanning differential mobility analyzer (DMA) has been widely employed for measurement of rapidly evolving aerosol size distributions. Interpretation of data from scanning DMAs is greatly facilitated when an exponential voltage ramp is prescribed, since the shape of the instrumental transfer function remains constant throughout a scan. However, that transfer function may differ significantly from that expected for fixed voltage operation. Because no simple analytical description of the scanning DMA transfer function exists, it has been evaluated numerically by simulating particle trajectories within a TSI 3081 cylindrical DMA. These computations yield transfer functions for the DMA up scan that are roughly triangular but with widths significantly greater than those for fixed voltage operation, and transfer functions for the down scan that are highly asymmetric. The impact of these distortions is most obvious when the size distribution of the measured aerosol is narrow, but errors in recovered size and concentration can be significant even when the aerosol size distribution is much broader than the transfer function. The magnitude of these errors is dependent upon the ratio of the mean gas residence time to the exponential voltage time constant, the sheath-to-aerosol-flow ratio, and the technique used to determine the instrument plumbing time. Experimental results for scans across broad and narrow size distributions compare favorably with predictions based on the simulated transfer functions. Simplified corrections are provided that can be used to adjust the concentration and mobility of size distributions recovered using a fixed voltage transfer function.
Innate Immunity and Inflammation in Sepsis: Mechanisms of Suppressed Host Resistance in Mice Treated with Ethanol in a Binge-Drinking Model

Sepsis is a major cause of mortality worldwide. Acute or chonic ethanol exposure typically suppresses innate immunity and inflammation and increases the risk of mortality in patients with sepsis. The study described here was designed to address the mechanism(s) by which acute ethanol exposure alters the course of sepsis. Ethanol administered to mice shortly before Escherichia coli (injected ip to produce sepsis) decreased production of proinflammatory cytokines and chemokines for several hours. Bacteria in the peritoneal cavity decreased over time in control mice and were mostly cleared by 21 h, but in ethanol-treated mice, bacteria increased over time to more than 2 × 108 at 21 h. Killing of bacteria in macrophages and neutrophils was apparently compromised by ethanol, as the percentage of these cells that had cleared phagocytosed bacteria increased over time in control mice but not in ethanol-treated mice. The roles of TLR4, MyD88, and myeloperoxidase (MPO) were evaluated using mutant or knockout mice, and these experiments indicated that mice with hyporesponsive TLR4 survived better than those with normal TLR4. Lack of MyD88 or MPO did not significantly alter survival in the presence or absence of ethanol. Ethanol decreased survival in all groups. This indicates that the antimicrobial activities induced though TLR4 are dispensable for survival but contribute to lethality late in the course of sepsis. Thus, the effects of ethanol responsible for lethal outcome in sepsis are not dependent on inhibition of TLR4 signaling, as we and others had previously suspected.
Activity Motifs Reveal Principles of Timing in Transcriptional Control of the Yeast Metabolic Network

Chechik et al. define activity motifs, which extend the concept of a network motif from the static to the dynamic realm. Mapping functional data onto network structure enables them to reveal new systems-level principles describing how yeast cells integrate exogenous signals and use transcriptional regulation to optimize metabolic responses to environmental perturbations. Significant insight about biological networks arises from the study of network motifs—overly abundant network subgraphs1,2—but such wiring patterns do not specify when and how potential routes within a cellular network are used. To address this limitation, we introduce activity motifs, which capture patterns in the dynamic use of a network. Using this framework to analyze transcription in Saccharomyces cerevisiae metabolism, we find that cells use different timing activity motifs to optimize transcription timing in response to changing conditions: forward activation to produce metabolic compounds efficiently, backward shutoff to rapidly stop production of a detrimental product and synchronized activation for co-production of metabolites required for the same reaction. Measuring protein abundance over a time course reveals that mRNA timing motifs also occur at the protein level. Timing motifs significantly overlap with binding activity motifs, where genes in a linear chain have ordered binding affinity to a transcription factor, suggesting a mechanism for ordered transcription. Finely timed transcriptional regulation is therefore abundant in yeast metabolism, optimizing the organism's adaptation to new environmental conditions.
Effect of Patient Arm Motion in Whole-Body PET/CT

Arm motion during whole-body PET/CT acquisition is not uncommon and can give rise to striking cold artifacts on PET images. We investigated the mechanisms that underlie these artifacts and proposed a potential solution. Methods: A phantom experiment based on 5 clinical cases of suspected arm motion was designed. The experiment involved a central 20-cm-diameter 68Ge/68Ga cylinder simulating the neck and 2 peripheral 10-cm-diameter 18F cylinders simulating arms. After motion-free CT and PET on a whole-body PET/CT system, the position of the arms was altered so as to introduce different amounts of misalignment. Twenty sequential PET scans were acquired in this position, alternating between 2-dimensional (2D) and 3-dimensional (3D) acquisition, as the 18F decayed. Decay of 18F in the arms, while the activity in the 68Ge/68Ga cylinder remained approximately constant, allowed the relative impact of scatter and attenuation-correction errors to be determined. Results: Image artifacts were largely confined to the local region of motion in 2D but extended throughout the affected slices in 3D, where they manifested as a striking underestimation of radiotracer concentration that became more significant with increasing misalignment. For 3D, scatter-correction error depended on activity in the arms, but for typical activity concentrations scatter-correction error was more significant than attenuation-correction error. 3D image reconstruction without scatter correction substantially eliminated these artifacts in both phantom and patient images. Conclusion: Reconstruction artifacts due to patient arm motion can be substantial and should be recognized because they can affect both qualitative and quantitative assessment of PET.
Characteristics of Primary and Secondary Hepatic Malignancies Associated with Hepatopulmonary Shunting

Tumor characteristics may identify high hepatopulmonary shunt cases, which indicated the need for interventions to reduce lung shunt fractions; the low incidence of acute radiation pneumonitis and radiation fibrosis after yttrium 90 radioembolization (RE) provide a basis for future studies evaluating a more streamlined RE process deferring technetium 99m macroaggregated albumin scanning.
Recursive Bayesian Decoding of Motor Cortical Signals by Particle Filtering

The population vector (PV) algorithm and optimal linear estimation (OLE) have been used to reconstruct movement by combining signals from multiple neurons in the motor cortex. While these linear me...
Learning from Human-Generated Lists

Human-generated lists are a form of non-iid data with important applications in machine learning and cognitive psychology. We propose a generative model -- sampling with reduced replacement (SWIRL) -- for such lists. We discuss SWIRL's relation to standard sampling paradigms, provide the maximum likelihood estimate for learning, and demonstrate its value with two real-world applications: (i) In a "feature volunteering" task where non-experts spontaneously generate feature ⇒ label pairs for text classification, SWIRL improves the accuracy of state-of-the-art feature-learning frameworks. (ii) In a "verbal uency" task where brain-damaged patients generate word lists when prompted with a category, SWIRL parameters align well with existing psychological theories, and our model can classify healthy people vs. patients from the lists they generate.
Heterogeneous Catalysis with Cross‐Linked Lyotropic Liquid Crystal Assemblies: Organic Analogues to Zeolites and Mesoporous Sieves

Organic, nanoporous heterogeneous catalysts based on a carboxylate-containing, amphiphilic mesogen catalyze the Knoevenagel condensation (see schematic representation). These networks maintain their order in solution and can be recycled. Enhanced basicity, excellent site accessibility, and substrate size exclusion are features of these nanostructured systems.
Mechanisms of soil carbon accrual and storage in bioenergy cropping systems

Annual row cropping systems converted to perennial bioenergy crops tend to accrue soil C, likely a function of increased root production and decreased frequency of tillage; however, very little is known about the mechanisms governing the accrual and stability of this additional soil C. To address this uncertainty, we assessed the formation and stability of aggregates and soil organic C (SOC) pools under switchgrass, giant miscanthus ,a native perennial grass mix and continuous corn treatments in Michigan and Wisconsin soils differing in both texture and mineralogy. We isolated different aggregate size fractions, >2 mm, 0.5–2 mm, and 2m m aggregates, and higher under the perennial grasses compared to corn. Contrastingly, in Wisconsin soils, microbial activities were highest in the <0.5 mm aggregates and evidence for soil C accrual under perennial grasses was observed only in a fast turnover pool in the <0.5 mm aggregate class. Our results help explain cross-site variability in soil C accrual under perennial bioenergy crops by demonstrating how interactions between belowground productivity, soil type, aggregation processes and microbial communities influence the rates and extent of SOC stabilization. Bioenergy cropping systems have the potential to be low-C energy sources but first we must understand the complex interactions controlling the formation and stabilization of SOC if we are to maximize soil C accrual.