cssi/SciSciGPT-SciSciNet huggingface dataset:
Trends of utilization and physician payments for vertebroplasty and kyphoplasty procedures by physician specialty and practice setting: 2010 to 2018.

Abstract Background Context In 2010, the American Academy of Orthopedic Surgeons published guidelines strongly recommending against the use of vertebroplasty following the publication of randomized control trials that failed to show significant improvement in pain. Vertebroplasty has remained controversial since those findings. Purpose To study and provide an update on utilization of vertebroplasty and kyphoplasty procedures among Medicare beneficiaries by physician specialty and practice setting following publication of recommendations against vertebroplasty in 2010. Study Design/Setting This study uses Medicare Part B Physician/Supplier Procedure Summary Master File (PSPSMF) for the years 2010 to 2018 to determine trends in volume and reimbursement by physician specialty and practice setting. Patient Sample All vertebral augmentation procedures with a physician reimbursement claims approved by Medicare Part B from 2010 to 2018. Outcome Measures This study analyzes trends in volume and physician payment of vertebroplasty and kyphoplasty procedures by physician specialty for the time period 2010 to 2018. Methods Claims from the Medicare Part B PSPSMF for the years 2010 to 2018 were extracted using the Current Procedural Terminology codes for vertebroplasty and kyphoplasty. Total volumes, payment amounts (professional component), and trends were analyzed by physician specialty. Results Between 2010 and 2018, the total volume of vertebroplasties decreased by 61.2% (29,995 to 11,654), whereas the volume of kyphoplasties increased modestly by 14.4% (59,691 to 68,294). Radiologists performed an increasing share of both procedures over this time period, from 68.5% to 75.1% for vertebroplasties and 28.9% to 37.1% for kyphoplasties. Total payment for vertebroplasties decreased by 74.3% from $14.8 million in 2010 to $3.8 million in 2018; whereas it increased by 235.3% for kyphoplasty procedures from $26.7 million to $89.7 million. This is driven in large part by a 6,833% increase in office based kyphoplasties which bill at the higher nonfacility rate that incorporates overhead, staff, and equipment. Conclusions Previous studies have demonstrated mixed evidence for benefits of vertebroplasty procedures and decreasing volumes over time. Data show continued downtrend in vertebroplasty and increased utilization of kyphoplasty among Medicare beneficiaries. In addition, the growing number of kyphoplasties correlated with a sharp rise in volume and increased reimbursement for office-based procedures. Radiologists have been performing an increasing share of both procedures.
Statistical analysis of monitoring data regarding the state of Keshan disease in Henan province from 2004 to 2009

Objective To study the state and trends of Kesan disease in Henan province from 2004 to 2009. Methods Surveillance sites were selected: Guxian village of Luoning country from 2004 - 2007, Zuyang town of Lingbao city in 2008, and Shahe village of Lushi country in 2009. All residents of surveillance sites were examined by clinical and electrocardiogram, and suspected patients were inspected by chest X-ray to measure ardiothoracic ratio. Hair and wheat flour samples were collected and selenium levels were detected with hydride generation atomic fluorescence spectrometry. Results From 2004 to 2009, a total of 4034 people were examined.The numbers of chronic and latent KSD patients were 21 and 75 cases,respectively, and the incidence rates were 0.52%(21/4034) and 1.86%(75/4034), respectively . The number of abnormal electrocardiogram was 751 cases, and the incidence rate was 18.62%. The highest proportion of abnormal electrocardiogram was ST-T changes,accounting for 24.63%(185/751), followed by high-voltage, accounting for 18.11%(136/751), and left ventricular accounting for 13.85% (104/751). Sixty-one grain samples were collected and the wheat flour selenium level was averaged 0.034 mg/kg. Thirty hair samples were collected and the selenium median was 0.285 mg/kg. Conclusions The state of Keshan disease is in a steady state in Henna province, but higher rates of abnormal electrocardiogram is a serious problem and should be studied and prevented. Key words: Keshan disease; Electrocardiography; X-rays; Selenium; Epidemiologic surveillance
Quantum-Chemically Informed Machine Learning: Prediction of Energies of Organic Molecules with 10 to 14 Non-hydrogen Atoms

High-fidelity quantum-chemical calculations can provide accurate predictions of molecular energies, but their high computational costs limit their utility, especially for larger molecules. We have shown in previous work that machine learning models trained on high-level quantum-chemical calculations (G4MP2) for organic molecules with one to nine non-hydrogen atoms can provide accurate predictions for other molecules of comparable size at much lower costs. Here we demonstrate that such models can also be used to effectively predict energies of molecules larger than those in the training set. To implement this strategy, we first established a set of 191 molecules with 10-14 non-hydrogen atoms having reliable experimental enthalpies of formation. We then assessed the accuracy of computed G4MP2 enthalpies of formation for these 191 molecules. The error in the G4MP2 results was somewhat larger than that for smaller molecules, and the reason for this increase is discussed. Two density functional methods, B3LYP and ωB97X-D, were also used on this set of molecules, with ωB97X-D found to perform better than B3LYP at predicting energies. The G4MP2 energies for the 191 molecules were then predicted using these two functionals with two machine learning methods, the FCHL-Δ and SchNet-Δ models, with the learning done on calculated energies of the one to nine non-hydrogen atom molecules. The better-performing model, FCHL-Δ, gave atomization energies of the 191 organic molecules with 10-14 non-hydrogen atoms within 0.4 kcal/mol of their G4MP2 energies. Thus, this work demonstrates that quantum-chemically informed machine learning can be used to successfully predict the energies of large organic molecules whose size is beyond that in the training set.
Paramagnetic Shifts and Guest Exchange Kinetics in ConFe4-n Metal-Organic Capsules.

We investigate the magnetic resonance properties and exchange kinetics of guest molecules in a series of hetero-bimetallic capsules, [ConFe4-nL6]4- (n = 1-3), where L2- = 4,4'-bis[(2-pyridinylmethylene)amino]-[1,1'-biphenyl]-2,2'-disulfonate. H bond networks between capsule sulfonates and guanidinium cations promote the crystallization of [ConFe4-nL6]4-. The following four isostructural crystals are reported: two guest-free forms, (C(NH2)3)4[Co1.8Fe2.2L6]·69H2O (1) and (C(NH2)3)4[Co2.7Fe1.3L6]·73H2O (2), and two Xe- and CFCl3-encapsulated forms, (C(NH2)3)4[(Xe)0.8Co1.8Fe2.2L6]·69H2O (3) and (C(NH2)3)4[(CFCl3)Co2.0Fe2.0L6]·73H2O (4), respectively. Structural analyses reveal that Xe induces negligible structural changes in 3, while the angles between neighboring phenyl groups expand by ca. 3° to accommodate the much larger guest, CFCl3, in 4. These guest-encapsulated [ConFe4-nL6]4- molecules reveal 129Xe and 19F chemical shift changes of ca. -22 and -10 ppm at 298 K, respectively, per substitution of low-spin FeII by high-spin CoII. Likewise, the temperature dependence of the 129Xe and 19F NMR resonances increases by 0.1 and 0.06 ppm/K, respectively, with each additional paramagnetic CoII center. The optimal temperature for hyperpolarized (hp) 129Xe chemical exchange saturation transfer (hyper-CEST) with [ConFe4-nL6]4- capsules was found to be inversely proportional to the number of CoII centers, n, which is consistent with the Xe chemical exchange accelerating as the portals expand. The systematic study was facilitated by the tunability of the [M4L6]4- capsules, further highlighting these metal-organic systems for developing responsive sensors with highly shifted 129Xe resonances.
Using Satellite Images and Deep Learning to Identify Associations Between County-Level Mortality and Neighborhood Features

Abstract What is the relationship between mortality and satellite images as elucidated through the use of Convolutional Neural Networks? Background Following a century of increase, life expectancy in the United States has stagnated and begun to decline in recent decades. Using satellite images and street view images, prior work has demonstrated associations of the built environment with income, education, access to care and health factors such as obesity. However, assessment of learned image feature relationships with variation in crude mortality rate across the United States has been lacking. Objective We sought to investigate if county-level mortality rates in the U.S. could be predicted from satellite images. Methods Satellite images of neighborhoods surrounding schools were extracted with the Google Static Maps application programming interface for 430 counties representing approximately 68.9% of the US population. A convolutional neural network was trained using crude mortality rates for each county in 2015 to predict mortality. Learned image features were interpreted using Shapley Additive Feature Explanations, clustered, and compared to mortality and its associated covariate predictors. Results Predicted mortality from satellite images in a held-out test set of counties was strongly correlated to the true crude mortality rate (Pearson r=0.72). Direct prediction of mortality using a deep learning model across a cross-section of 430 U.S. counties identified key features in the environment (e.g. sidewalks, driveways and hiking trails) associated with lower mortality. Learned image features were clustered, and we identified 10 clusters that were associated with education, income, geographical region, race and age. Conclusions The application of deep learning techniques to remotely-sensed features of the built environment can serve as a useful predictor of mortality in the United States. Although we identified features that were largely associated with demographic information, future modeling approaches that directly identify image features associated with health-related outcomes have the potential to inform targeted public health interventions.
Experience with Diversity is Not Enough: A Pedagogical Framework for Teacher Candidates that Centers Critical Race Consciousness

Given the overwhelming whiteness of teacher education, we offer a pedagogical approach rooted in critical race theory, and draw on Carter’s (2008) notions of critical race consciousness to: 1) center a critical race perspective in methods-based coursework; and 2) employ critical race theory to analyze the function and role of clinical fieldwork. In this article, we provide examples of how we engage white teacher candidates to preemptively take stock of their own racial journey and biases prior to being responsible for educating students of color. We also focus on the process of selecting clinical placements and assignments. We explicate how current selection criteria for clinical sites and cooperating teachers are undergirded by systems of white supremacy, and problematize the reality of majority white clinical placements. We further provide suggestions for teacher education programs that pay particular attention to the roles and responsibilities of white teacher educators and predominantly white teacher education programs.
Perioperative Desensitization for Sensitized Lung Transplant Candidates

Purpose Sensitized lung transplant (LTx) candidates have longer waiting times, decreased likelihood of transplant, and increased risk of death while on waitlist. To mitigate this and to increase the access to donor pool, for sensitized candidates, we modified and implemented The Toronto perioperative strategy to treat DSA-positive recipients with positive virtual crossmatch (VCM) donor offers. We hypothesize that such perioperative desensitization strategy can be safely implemented with acceptable outcomes and help decrease the waitlist mortality. Methods We performed a retrospective chart review of sensitized candidates who underwent LTx between June 2017 - June 2020 and required perioperative desensitization. We collected the baseline demographics and post-transplant variables. The protocol was implemented if the calculated panel reactive antibody (cPRA) was > 30 % and had positive VCM. Desensitization protocol included preoperative plasma exchange (PLEX) with 1.5 volume, intra operative basiliximab induction, followed by five sessions of PLEX, intravenous immunoglobulin (IvIg, 1 gm / kg) and Anti Thymocyte globulin (dose 3 mg/kg for VCM positive vs 5 mg/kg for positive actual crossmatch (ACM)). We used tacrolimus (12 - 15 ng/ml), mycophenolate and prednisone for maintenance immunosuppression. Results 25 patients required desensitization. 76% (n=19) of them are females. Median LAS score is 41.3 (IQR 33.87-60.33). Median wait time was 28.9 days (IQR 12.6-65). All patients underwent bilateral lung transplantation. ACM was positive in 24% of patients (n=6). 76% (n=19) completed the protocol. Incidence of Primary graft dysfunction at any time point was 12% (n=3). Acute cellular rejection >= grade 2 was 8% (n=2). 8% (n=2) had chronic lung allograft dysfunction. Overall survival of this cohort is 96% with a median follow up of 17 months (IQR 5 - 25.5). Conclusion Perioperative desensitization can be safely implemented with acceptable outcomes in sensitized LTx candidates. On comparison of our SRTR data, before and after desensitization implementation, we noted a decline in the waitlist mortality (11.4% to 7.6%) and 50th percentile median wait times (8.5 months to 1.3 months).
The impact of botulinum injection for hospitalized children with Hirschsprung-associated enterocolitis

Stasis from obstruction at the level of the internal anal sphincter (IAS) can lead to Hirschsprung-associated enterocolitis (HAEC) and may be improved by botulinum toxin (BT) injections. Our aim was to determine if BT injection during HAEC episodes decreased the number of recurrent HAEC episodes and/or increased the interval between readmissions. A retrospective review was performed of patients admitted for HAEC from January 2010 to December 2019. Demographics and outcomes of patients who received BT were compared to patients who did not receive BT during their hospital stay. A total of 120 episodes of HAEC occurred in 40 patients; 30 patients (75%) were male, 7 (18%) had Trisomy 21 and 10 (25%) had long-segment disease. On multivariate analysis, patients who received BT during their inpatient HAEC episode had a longer median time between readmissions (p = 0.04) and trending toward an association with fewer readmissions prior to a follow-up clinic visit (p = 0.08). The use of BT in HD patients hospitalized for HAEC is associated with an increased time between recurrent HAEC episodes and trended toward fewer recurrent episodes. The use of BT should be considered in the management of patients admitted with HAEC.
Prey type constrains growth and photosynthetic capacity of the kleptoplastidic ciliate Mesodinium chamaeleon (Ciliophora)

Kleptoplastidic, or chloroplast-stealing, lineages offer insight into the process of acquiring photosynthesis. By quantifying the ability of these organisms to retain and use photosynthetic machinery from their prey, we can understand how intermediaries on the endosymbiosis pathway might have evolved regulatory and maintenance mechanisms. Here, we focus on a mixotrophic kleptoplastidic ciliate, Mesodinium chamaeleon, noteworthy for its ability to retain functional chloroplasts from at least half a dozen cryptophyte algal genera. We contrasted the performance of kleptoplastids from blue-green and red cryptophyte prey as a function of light level and feeding history. Our experiments showed that starved M. chamaeleon cells are able to maintain photosynthetic function for at least 2 weeks and that M. chamaeleon containing red plastids lost chlorophyll and electron transport capacity faster than those containing blue-green plastids. However, likely due to increased pigment content and photosynthetic rates in red plastids, M. chamaeleon had higher growth rates and more prolonged growth when feeding on red cryptophytes. For example, M. chamaeleon grew rapidly and extensively when fed the blue-green cryptophyte Chroomonas mesostigmatica, but this growth appeared to hinge on high levels of feeding supporting photosynthetic activity. In contrast, even starved M. chamaeleon containing red plastids from Rhodomonas salina could achieve high photosynthetic rates and extensive growth. Our findings show that plastid origin impacts the maintenance and magnitude of photosynthetic activity, though whether this is due to variation in ciliate control or gradual loss of plastid function in ingested prey cells remains unknown.
Variation in clinical characteristics, outcomes, and mortality of hospitalized patients with COVID-19 during the second wave of the pandemic: a single-center experience.

As of February 2, 2021, the USA has 26,431,799 reported COVID-19 cases with 446,744 deaths. A high mortality rate (15%-40%) was reported among hospitalized patients with COVID-19 during the first wave of the pandemic. However, data regarding variation in COVID-19-related mortality and severity of illness among hospitalized patients with COVID-19 are heterogeneous. In this retrospective single-center study, we aimed to investigate the demographic characteristics, clinical presentations, disease severity, clinical outcomes, and in-hospital mortality of hospitalized patients with COVID-19 during the second wave of the pandemic. Adults with reverse transcription-PCR-confirmed SARS-CoV-2 infection were included. In-hospital mortality due to COVID-19 was the primary outcome, and intensive care unit admission, acute kidney injury, acute respiratory distress syndrome, respiratory failure requiring intubation, and septic shock were the secondary outcomes. A total of 101 adult patients were hospitalized with COVID-19 during the second wave study period. Of 101 patients, 8 were intubated and 6 died. The median duration of hospital stay was 6 days. Patients in the second wave were more likely to receive dexamethasone and remdesivir and less likely to require invasive mechanical ventilation. In-hospital mortality during the second wave was lower (5.9%) compared with the first wave (15.5%). At the last follow-up date, 86.1% were discharged alive from the hospital, 5.9% died and 7.9% were still in the hospital. Multivariate logistic regression showed higher odds of mortality were associated with higher age and elevated lactate dehydrogenase peak.
The Association Between Age of Initiation and Current Blunt Use among Adults: Findings from the National Survey on Drug Use and Health, 2014-2019

Abstract Background Initiating cannabis use at a young age has been linked to problematic and continued cannabis use in adulthood. Given that approximately 1 in 3 adult cannabis smokers report blunt use, it is important to determine if and how age of blunt initiation is associated with current blunt use among adult blunt smokers. Methods This study uses cross-sectional pooled data from the 2014-2019 National Survey on Drug Use and Health (NSDUH) to examine the association between age of blunt initiation and current blunt use among 62,020 adults who reported lifetime blunt use. Results Among lifetime blunt smokers, 51.4% initiated blunt use at 18 years or older, 42.1% initiated blunt use at 14 to 17 years old and 6.5% initiated blunt use at 13 years or younger. Multivariable logistic regression models revealed that odds of past 12-month (aOR: 1.58; 95% CI: 1.45 – 1.72), past 30-day (aOR: 2.58; 95% CI: 2.37 – 2.80) and daily (aOR: 3.17; 95% CI: 2.61 – 3.86) blunt use were greater among adults who initiated blunt use at 13 years of age or younger relative to those who initiated blunt use at 18 years of age or older, controlling for covariates. Conclusions Early onset of blunt use among adolescents is associated with current blunt use in adulthood among lifetime blunt users. Given the adverse health effects associated with blunt use and the prevalence of adult cannabis users who report blunt use, cannabis interventions and policies should be expanded to target blunt use among early initiators.
Clostridioides difficile spore germination: initiation to DPA release

Germination by Clostridioides difficile spores is an essential step in pathogenesis. Spores are metabolically dormant forms of bacteria that resist severe conditions. Work over the last 10 years has elucidated that C. difficile spores germinate thorough a novel pathway. This review summarizes our understanding of C. difficile spore germination and the factors involved in germinant recognition, cortex degradation and DPA release.
Comparison of Pilot and Automation Generated Lateral Conflict Resolutions

This study compares and contrasts lateral conflict resolutions generated by pilots (with and without a set of decision support tools), with those generated by a fully automated conflict resolution tool that generates optimal (smallest path deviation) resolutions. The conflict geometries investigated were all factorial combinations of three levels of Intruder aircraft speed, three levels of initial Ownship distance to closest approach, and nine conflict angles. The resolution decision support tools included dynamic conflict alerting, which indicated whether a proposed path was conflict free, and a dynamic predictor system that showed a fast time depiction of the proposed resolution trajectories. The automation-generated resolutions, computed using a geometric optimization algorithm, served as a benchmark against which the pilot-generated resolutions were compared. Without decision support tools the pilot-generated resolutions were often ineffective in providing the necessary separation, particularly at sma...
Predictors for detection of cancer in patients with indeterminate biliary stricture and atypical cells on endoscopic retrograde brush cytology

Objective The management of atypical cells on endoscopic retrograde brush cytology (ERBC) in patients with indeterminate biliary stricture is unclear. This study aimed to investigate the detection of cancer (pancreatic and biliary carcinoma) in patients with atypical cells on ERBC and the factors predicting it. Methods From a prospectively maintained cytology database in a tertiary care center, patients with indeterminate biliary stricture and atypical cells on ERBC from 1996 to 2012 were studied. The date of the initial ERBC with atypical cells was identified as time zero. The primary outcome was to study the incidences and Kaplan–Meier estimates for detecting cancer. Results In all, 104 patients with 182.8 person-years of follow-up were identified. In 38 (36.5%) patients cancer was detected (19 cholangiocarcinoma, 15 pancreatic cancer, three ampullary cancer and one gallbladder carcinoma) over a mean follow-up of 4.4 months. On Cox regression analysis, the presence of clinical jaundice (hazard ratio [HR] 4.08, 95% CI 1.41–11.8), active alcohol consumption (HR 7.33, 95% CI 1.85–29.1) and elevated carbohydrate antigen 19-9 (CA19-9) level (>33 U/mL) (HR 8.42, 95% CI 1.75–40.6) at the time of ERBC were associated with increased risk for the detection of cancer. Detection of cancer was more common during the first 6 months of follow-up than at any time period thereafter. Conclusion Elevated CA19-9 level, the presence of clinical jaundice and current alcohol consumption are associated with increased detection of cancer in patients with indeterminate biliary stricture and atypical cells on ERBC.
Immigrant Enclaves and the Success of Entrepreneurial Ventures

The present work explores the characteristics of entrepreneurs and their environments that are related to entrepreneurial success. To this end, we examine the relationship between immigrant status and firm location decisions of entrepreneurs and their resultant firm profits and viability. To categorize location decisions, we focus on the concepts of immigrant and ethnic enclaves. Data on entrepreneurs and their beginning firms were provided by the Kauffman foundation and cover the years 2004-2008. These firm-level data are linked to Census 2000 Summary Files 3 and 4 at the zip-code level of measurement and are used to empirically investigate the effect of enclaves. We find no evidence for an effect of the nativity of firm owner on the entrepreneurial success of the firms. We find a statistically significant negative relationship between the immigrant representation in an area and firm profitability.
Conformational Differences in the Active Sites of Muscle and Erythrocyte Pyruvate Kinase

Abstract We have examined the inhibition of the allosteric pyruvic kinase isozyme of human erythrocytes (PK I) and of the nonallosteric pyruvic kinase isozyme of rabbit muscle (PK III) by iodoacetamide and the protection against this inhibition by substrates and cations. Both isozymes are inhibited in a similar fashion which can be accounted for by alkylation of two different groups on each isozyme, one with a pKa of less than 6.8 and the other with a pKa of 7.8. Under the experimental conditions used, the effects observed in the protection studies were predominantly those involving the group with a pKa below 6.8. The rabbit muscle enzyme is not protected from iodoacetamide inhibition by phosphoenolpyruvate, ADP, or magnesium alone. It is protected by potassium or the magnesium-ADP complex. At pH 7.4, the human erythrocyte enzyme is not protected by phosphoenolpyruvate, ADP, or magnesium alone, or by potassium or the magnesium-ADP complex. In the presence of either of the positive allosteric effectors of the erythrocyte enzyme, phosphoenolpyruvate or fructose 1,6-diphosphate, both potassium and the magnesium-ADP complex have a protective action. We conclude that PK I exists in two conformational states, one equivalent to the T form of the Monod, Wyman, and Changeaux, model (Monod, J., Wyman, J., and Changeaux, G. P., J. Mol. Biol., 12, 88 (1965)) with a low affinity for phosphoenolpyruvate and no affinity for potassium or the magnesium-ADP complex, and the other equivalent to the R form of this model with a high affinity for phosphoenolpyruvate, potassium, and magnesium-ADP. Binding of either phosphoenolpyruvate or fructose 1,6-diphosphate converts the T form into the R form. PK III always exists in the R form with a high affinity for phosphoenolpyruvate, potassium, and the magnesium-ADP complex. We have demonstrated a cooperative influence of phosphoenolpyruvate on potassium binding to the human erythrocyte enzyme which is consistent with this allosteric model.
Uia: a global connectivity architecture for mobile personal devices

The Internet's architecture, designed in the days of large, stationary computers tended by technically savvy and accountable administrators, fails to meet the demands of the emerging ubiquitous computing era. Nontechnical users now routinely own multiple personal devices, many of them mobile, and need to share information securely among them using interactive, delay-sensitive applications. Unmanaged Internet Architecture (UIA) is a novel, incrementally deployable network architecture for modern personal devices, which reconsiders three architectural cornerstones: naming, routing, and transport. UIA augments the Internet's global name system with a personal name system, enabling users to build personal administrative groups easily and intuitively, to establish secure bindings between his devices and with other users' devices, and to name his devices and his friends much like using a cell phone's address book. To connect personal devices reliably, even while mobile, behind NATs or firewalls, or connected via isolated ad hoc networks, UIA gives each device a persistent, location-independent identity, and builds an overlay routing service atop IP to resolve and route among these identities. Finally, to support today's interactive applications built using concurrent transactions and delay-sensitive media streams, UIA introduces a new structured stream transport abstraction, which solves the efficiency and responsiveness problems of TCP streams and the functionality limitations of UDP datagrams. Preliminary protocol designs and implementations demonstrate UlA's features and benefits. A personal naming prototype supports easy and portable group management, allowing use of personal names alongside global names in unmodified Internet applications. A prototype overlay router leverages the naming layer's social network to provide efficient ad hoc connectivity in restricted but important common-case scenarios. Simulations of more general routing protocols—one inspired by distributed hash tables, one based on recent compact routing theory—explore promising generalizations to UIA's overlay routing. A library-based prototype of UIA's structured stream transport enables incremental deployment in either OS infrastructure or applications, and demonstrates the responsiveness benefits of the new transport abstraction via dynamic prioritization of interactive web downloads. Finally, an exposition and experimental evaluation of NAT traversal techniques provides insight into routing optimizations useful in UIA and elsewhere. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)
Bounds on generalized structured singular values

The authors present several bounds on the structured singular value (SSV). They first adopt a generalized notion of which is useful for problems where uncertainties are assumed to be bounded in an l/sub p/-induced matrix norm. Two different types of bounds, in terms of Perron root and interaction parameters, respectively, are given for the new SSV, and their relations are discussed. These bounds are useful in that they are easy to compute and may be further analyzed to provide insights useful in design. >
Ultrafast and long-lived photoinduced charge separation in MEH-PPV/nanoporous semiconductor thin film composites

Photoinduced charge separation and recombination dynamics were investigated in composite materials of conjugated polymer deposited on nanocrystalline metal oxide thin film. Using femtosecond IR transient absorption spectroscopy, the electron transfer from the excited state of poly[2-methoxy-5-(2-ethyl-hexyloxy)-(phenylene vinylene)] (MEH-PPV) to SnO2 and TiO2 nanoporous thin films is shown to occur with timescales of 800 and <100 fs, respectively. Negligible carrier recombination is observed for MEH-PPV/SnO2 within 1 ns. Microsecond charge recombination dynamics were measured using step-scan FTIR. Long-lived charge separation is observed in both systems, persisting for microseconds to seconds.
A Model for Predicting Fracture Toughness of a Cementitious Particulate Composite Molded under Impact Pressure

The form of a model relating two influential compositional factors of a material to fracture toughness is identified. A similar, simpler form is proposed for regression analyses. Demonstration of the utility of the model is accomplished using experimental results from testing of a portland cement stabilized fine grained soil.
Cytosine arabinoside modulation of the mitotic index in treatment of adult acute leukemia

Twenty-three unselected adult acute leukemic patients were treated with an initial intravenous pulse of cytosine arabinoside (Ara-C) 5 mg/kg. The mean mitotic index dropped from 7.7/1,000 to 2.8/1,000 at 4 hours after Ara-C pulse and rebounded to 6.7/1,000 at 18 hours. Infusions of Ara-C 7--10 mg/kg were given for 9 or 12 hours, depending on changes in the mitotic index. The group of responders (M1 or M2 marrows) could be predicted by the initial blast count in the marrow and the change in the mitotic index 18 hours after the Ara-C pulse. There were 9 (39%) complete and partial remissions. Six patients remained in remission more than 200 days. Since the changes in the mitotic indices induced by Ara-C were indistinguishable from those of another more successful trial, we infer that factors other than modulation of the cell cycle are critical to the success of this mode of therapy.
How to determine whether existing human embryonic stem cell lines can be used ethically.

International Society for Stem Cell Research. (2006). Guidelines for the conduct of human embryonic stem cell research. http://www.isscr.org/guidelines/index.htm.Merriam-Webster Online. (2008). “Provenance.” http://www.merriam-webster.com/dictionary/provenance.Stemride International. (2008). List of hESC lines. http://www.stemride.com/products_lines.htm.
Mercury's crust likely made of magnesium-rich basalt

With both X-ray and gamma-ray spectrometers, the MErcury Surface, Space ENvironment, GEochemistry and Ranging probe (MESSENGER), which entered orbit around Mercury in 2011, is well equipped for carrying out a detailed compositional analysis of Mercury's crust, the understanding of which could help determine the nature of the planet's formation and of its volcanic past.
Temperature, periodicity and horizons

Abstract We explain and explore the connections among the following propositions: (1) thermal equilibrium is characterized by the KMS condition, 〈At−iβB〉 = 〈BAt〉; (2) finite-temperature Green functions are periodic in imaginary time; (3) black holes are hot; and to an accelerating observer, empty space is hot. The KMS condition of quantum statistical mechanics is derived, with special attention to quantum field systems satisfying relativistic commutation relations and linear field equations. We display the analytic structure of the two-point function and show in what sense the KMS condition for such systems is a statement of periodicity. Then the application of these ideas to horizons in general-relativistic settings is reviewed. Other matters discussed include: the identification of the analytically continued two-point function with the Green function of an elliptic (“Euclideanized”) operator; the analogous relation between a nonrelativistic propagator and a parabolic operator; the construction of thermal two-point functions as image sums; the (in)significance of time ordering; simplications of the KMS condition in the presence of discrete symmetries; the appearance of a “double” Fock space (artificially in general statistical mechanics, but naturally in space-times with horizons); and complications associated with the infrared behavior of the “particle” spectrum.
Promoting connection: Perspective-taking improves relationship closeness and perceived regard in participants with low implicit self-esteem

Abstract Previous research suggests that people with low implicit self-esteem may be less connected to their close relationship partners (e.g., Peterson & DeHart, 2013; DeHart, Pelham, Fiedorowicz, Carvallo & Gabriel, 2011). The current study suggests that this effect can be reduced with a perspective-taking manipulation. Results revealed that, in the control condition, people with low implicit self-esteem were less close to their relationship partners and reported lower perceived regard. In the perspective-taking condition, people high and low in implicit self-esteem did not differ in closeness or perceived regard. This was due to a significant increase in closeness and perceived regard among low implicit self-esteem participants in the perspective-taking (vs. control) condition. These findings replicate the negative relationship between implicit self-esteem and relationship closeness, while also offering a method by which this relationship can be attenuated.
Miniature In Vivo Robotics and Novel Robotic Surgical Platforms

Robotic surgical systems, such as the da Vinci Surgical System (Intuitive Surgical, Inc., Sunnyvale, California), have revolutionized laparoscopic surgery but are limited by large size, increased costs, and limitations in imaging. Miniature in vivo robots are being developed that are inserted entirely into the peritoneal cavity for laparoscopic and natural orifice transluminal endoscopic surgical (NOTES) procedures. In the future, miniature camera robots and microrobots should be able to provide a mobile viewing platform. This article discusses the current state of miniature robotics and novel robotic surgical platforms and the development of future robotic technology for general surgery and urology.
Ground truth for evaluating 6 degrees of freedom pose estimation systems

Systems developed to estimate poses of objects in 6 degrees of freedom (6DOF) Cartesian space (X, Y, and Z coordinates plus roll, pitch, and yaw) are reliant on the vendors' own processes to determine performance and measurement accuracy. These practices are not yet standardized, and are rarely reported by the vendors in sufficient detail to enable users and integrators to recreate the process. Efforts must therefore be made to enable the documented and, more importantly, independently repeatable evaluation of such systems using standardized processes, fixtures, and artifacts. In this paper, we describe three 6DOF ground truth systems utilized at the National Institute of Standards and Technology (NIST): a laser-tracker-based system for pose measurement, an aluminum fixture-based system that can be used to set the pose of artifacts, and a modular, medium-density fiberboard (MDF) fixture system. Descriptions, characterizations, and measured accuracies of these systems are provided for reference.
The gradient expansion approximation for exchange: A physical prespective

In recent work, we have provided a rigorous physical interpretation for the exchange energy and potential (or functional derivative) as obtained within the local-density approximation via the Harbola–Sahni formulation of many-electron theory. In this article, we analyze the gradient-expansion approximation (GEA) for these properties from the same physical perspective. The source charge distribution in this approximation is the GEA Fermi hole to O(▽3). This charge distribution is unphysical, so that the resulting force field and work done cannot be defined in a physically meaningful manner, and the exchange energy is singular. Thus, when viewed from the perspective of a source charge, the existence of the gradient expansions for the potential and energy is questionable. We next discuss the conventional method of employing a screened-Coulomb interaction to eliminate the singularities due to the GEA source charge, and show that it leads to inconsistent results. These inconsistencies are also intrinsic to a proof of the inequivalence of the Harbola–Sahni and Kohn–Sham exchange potentials within the GEA. Thus, although the inequivalence of these potentials has been established by other analyses, this proof is shown not to be rigorous. Finally, we demonstrate that when the physics of the GEA exchange source charge is corrected by the satisfaction of sum rules, the modified charge distribution then leads to a well-behaved local exchange potential and exchange energy density, and to a finite exchange energy. The consequences of our analysis on the gradient expansions for the correlation and exchange-correlation potential and energy are also noted. © 1992 John Wiley & Sons, Inc.
Thymocytes can be stimulated to give a strong vaccinia virus-immune cytotoxic T lymphocyte response

The emergence of virus-specific cytotoxic T lymphocyte (CTL) precursors in thymus can be examined directly by stimulating thymocytes for 6 days in irradiated, virus-infected recipients. Responsiveness is a characteristic of the thymocytes themselves and does not reflect the presence of contaminating, blood-bourne T cells. Strong CTL activity may be generated earlier from thymus than from spleen or lymph node of lethally irradiated, bone marrow reconstituted mice. Also, the reconstitution of virus-immune CTL function in these peripheral lymphoid organs is thymus-dependent. Use of this simple experimental protocol offers considerable possibilities for the analysis of the role of the thymus in the ontogeny of the T cell repertoire.
Psychosocial factors and the rehabilitation of patients with chronic work-related upper extremity disorders

This prospective cohort study investigated the effects of psychosocial factors on long-term employment outcome of a sample of chronic work-related upper-extremity pain disorder patients who had completed an interdisciplinary functional restoration program. Factors examined included the following: DSM-III-R Axis I and Axis II diagnoses, derived from the Structured Clinical Interview for DSM-III-R (SCID); history of childhood abuse experienced as elicited by the SCID; the Quantitated Pain Drawing, which evaluated perceived pain intensity; Million Visual Analog Scale, which measures perceived level of disability; and the Beck Depression Inventory, which assessed the level of depression. Results from univariate analyses demonstrated that return-to-work status 1 year following rehabilitation was predicted by the following psychosocial variables: The number of Axis I disorders, a past diagnosis of substance abuse, a past and/or current diagnosis of an anxiety disorder, a diagnosis of borderline personality disorder, a history of childhood abuse, self-report of depressed mood, and a moderate to high level of perceived disability. Additionally, age, race, length of disability, and prior surgical treatment predicted return-to-work rates. A multiple logistic regression further revealed that upper extremity patients who were older, Caucasian, had a current diagnosis of an anxiety disorder, and whose perception of their disability deteriorated from pre- to post-program were significantly less likely to return to work at one-year follow-up. Overall, the findings indicate that psychosocial variables influence the successful rehabilitation of patients with upper extremity disability, suggesting that these patients should be assessed and treated for psychosocial dysfunctions in conjunction with their rehabilitation so as to optimize favorable outcomes after treatment.
Behavioural ecology of Tropidurus hispidus on isolated rock outcrops in Amazonia

A population of the tropical lizard Tropidurus hispidus , isolated on a granitic rock outcrop in tropical forest of northern Brazil, was studied during the 1993 wet season. Four types of observational studies revealed that lizards are active throughout most of the day. During 10-minute intervals, individual lizards moved five times for an average of 240 cm and tongue-flicked once. Habitat temperatures vary considerably during the day, with rock and air temperatures in sun exceeding body temperatures of lizards during much of the activity period. During most of the day, lizards thermoregulate by moving among shady, filtered sun, and sunny microhabitats maintaining body temperatures near 35°C. Temperatures of lizards active during cloudy periods were significantly lower than temperatures of lizards during sunny periods, indicating that clouds decrease the ability of lizards to effectively thermoregulate. Most feeding occurs in the afternoon at edges of rock outcrops with ants, insect larvae, termites and beetles dominating the diet. Comparisons with a near-by savanna population revealed differences in body size (males only), activity period (longer on rocks), body temperatures (higher on rocks), number of prey categories consumed (lower on rocks), mean size of prey (larger on rocks), number of prey eaten (fewer on rocks) and microhabitat use (more restricted on rocks).
Theory of the magnetic polaron

We construct exact Green's functions for a single electron in a ferromagnetic semiconductor, including both spin-conserving and spin-flip processes at $T=0$. We contrast two cases: ferromagnetic and antiferromagnetic coupling of the electron's spin to the lattice. In the former case, a small-$k$ electron will have its spin totally polarized in the predominant direction, whereas in the latter, deviation from saturation polarization is to be expected. Crucial differences between bound- and scattering-state contributions to the electron's spectral weight are highlighted.
Conductance, contacts, and interface states in single alkanedithiol molecular junctions

We calculate the conductance of Au-alkanedithiol-Au molecular junctions from first principles, finding agreement with measured data [B. Xu and N. J. Tao, Science 301, 1221 (2003)] for junctions where the terminal S atoms are attached to top sites of the gold electrodes. A major effect of the contact geometry on the conduction properties is found, whose origin is traced to the symmetry and spatial localization of the interface states. The implications of our finding to ongoing experiments are noted.
Cable equation for a myelinated axon derived from its microstructure

A simplified cable equation that describes the subthreshold behaviour of a myelinated axon is derived from its microstructure. Specifically, a microcontinuum cable model of a composite axon is homogenised, yielding a familiar macrocontinuum cable equation of electrotonus, for which the space and time constants depend on microstructural electrical parameters. Activating functions for magnetic and electrical stimulation can be incorporated into this homogenised cable equation as sources or sinks of transmembrane potential. An integral solution to the forced cable equation is also presented for the subthreshold regime. Errors are introduced when myelin membrane resistance is assumed to be infinite.
Gingival hyperplasia: a side effect of nifedipine and diltiazem

Currently, calcium channel blockers are being used increasingly for the treatment of hypertension in the elderly. Several case reports in the dental literature suggest that patients treated with the calcium channel blockers manifest gingival hyperplasia similar to that seen in patients taking phenytoin (Dilantin, Parke-Davis). A small study of 89 patients undertaken at the Westside Veterans Administration Medical Center, Chicago seems to indicate that nifedipine and diltiazem do indeed cause gingival hyperplasia. A total of 83% of the patients studied receiving nifedipine showed evidence of hyperplastic tissue and 74% of those on diltiazem were found to have hyperplastic tissue.
LET'S STICK TOGETHER: UNDERSTANDING AFRICA'S SECESSIONIST DEFICIT

Over the last 40 years, Africa has experienced relatively fewer secessionist conflicts than most other regions of the world, even though it is otherwise plagued with political violence and its countries tend to display a higher prevalence of many of the factors usually associated with separatism. After empirically establishing Africa’s secessionist deficit, this article reviews the few existing explanations for it before articulating a theory which singles out the benefits to African regional elites (and those who depend on them) of weak sovereign states. In Africa as elsewhere, the article argues, regional leaders can be expected to capitalize on local grievances and promote secessions if the potential rewards of a separatist state, in the absence of international recognition, outweigh the potential rewards associated with control or partial control of institutions of the sovereign national state. What distinguishes African elites is the relatively greater material returns to sovereignty that they face. Given the continent’s poverty, the undiversified nature and commodity dependence of its economies, and the relative lack of accountability of state power, Africa offers a significant material premium to internationally recognized sovereignty, tilting the odds for elites in favour of staying within the state, even if they do not immediately benefit from power at the centre. The article then tests the argument against actual African cases of secession, showing that they are usually a function of variations in the relative rewards of sovereignty. In conclusion, it argues that Africa’s weak sovereignty equilibrium has contributed to its failure to develop. IN ABOUT 40 YEARS OF INDEPENDENCE, only ten of sub-Saharan Africa’s 48 states have experienced a secessionist conflict, and most of these have been short-lived, quite minor in scope, and unsuccessful. In contrast, over the same period, 30 African states have provided the stage for at least one nonsecessionist domestic conflict, many of which have been drawn out and quite