bluuebunny/crossref_metadata_2025 huggingface dataset:
Observation of suppressed terahertz absorption in photoexcited graphene
Authors: Frenzel A. J. , Lui C. H. , Fang W. , Nair N. L. , Herring P. K. , Jarillo-Herrero P. , Kong J. , Gedik N.
Published: March 2013

When light is absorbed by a semiconductor, photoexcited charge carriers enhance the absorption of far-infrared radiation due to intraband transitions. We observe the opposite behavior in monolayer graphene, a zero-gap semiconductor with linear dispersion. By using time domain terahertz (THz) spectroscopy in conjunction with optical pump excitation, we observe a reduced absorption of THz radiation in photoexcited graphene. The measured spectral shape of the differential optical conductivity exhibits non-Drude behavior. We discuss several possible mechanisms that contribute to the observed low-frequency non-equilibrium optical response of graphene.
A low energy beam transport system for proton beam
Authors: Yang Y. , Zhang Z. M. , Wu Q. , Zhang W. H. , Ma H. Y. , Sun L. T. , Zhang X. Z. , Liu Z. W. , He Y. , Zhao H. W. , Xie D. Z.
Published: March 2013

A low energy beam transport (LEBT) system has been built for a compact pulsed hadron source (CPHS) at Tsinghua University in China. The LEBT, consisting of two solenoids and three short-drift sections, transports a pulsed proton beam of 60 mA of energy of 50 keV to the entrance of a radio frequency quadrupole (RFQ). Measurement has shown a normalized RMS beam emittance less than 0.2 π mm mrad at the end of the LEBT. Beam simulations were carried out to compare with the measurement and are in good agreement. Based on the successful CPHS LEBT development, a new LEBT for a China ADS projector has been designed. The features of the new design, including a beam chopper and beam simulations of the LEBT are presented and discussed along with CPHS LEBT development in this article.
Photoluminescence and pressure effects in short period InN/nGaN superlattices
Authors: Staszczak G. , Gorczyca I. , Suski T. , Wang X. Q. , Christensen N. E. , Svane A. , Dimakis E. , Moustakas T. D.
Published: March 2013

Measurements of photoluminescence and its dependence on hydrostatic pressure are performed on a set of InN/nGaN superlattices with one InN monolayer and with different numbers of GaN monolayers. The emission energies, EPL, measured at ambient pressure, are close to the value of the band gap, Eg, in bulk GaN, in agreement with other experimental findings. The pressure dependence of the emission energies, dEPL/dp, however, resembles that of the InN energy gap. Further, the magnitudes of both EPL and dEPL/dp are significantly higher than those obtained from ab-initio calculations for 1InN/nGaN superlattices. Some causes of these discrepancies are suggested.
Optical in situ monitoring of hydrogen desorption from Ge(100) surfaces
Authors: Barrigón Enrique , Brückner Sebastian , Supplie Oliver , Kleinschmidt Peter , Rey-Stolle Ignacio , Hannappel Thomas
Published: March 2013

Molecular hydrogen strongly interacts with vicinal Ge(100) surfaces during preparation in a metal organic vapor phase epitaxy reactor. According to X-ray photoemission spectroscopy and Fourier-transform infrared spectroscopy results, we identify two characteristic reflection anisotropy (RA) spectra for H-free and monohydride-terminated vicinal Ge(100) surfaces. RAS allows in situ monitoring of the surface termination and enables spectroscopic hydrogen kinetic desorption studies on the Ge(100) surface. Comparison of evaluated values for the activation energy and the pre-exponential factor of H desorption evaluated at different photon energies reflects that H unevenly affects the shape of the RA spectrum.
Bandgap narrowing in high dopant tin oxide degenerate thin film produced by atmosphere pressure chemical vapor deposition
Authors: Lin Yang-Yi , Lee Hsin-Yi , Ku Ching-Shun , Chou Li-Wei , Wu Albert T.
Published: March 2013

Antimony-doped tin oxide (SnO2:Sb) thin films were prepared by atmospheric pressure chemical vapor deposition. Precursors were mixed with gaseous SnCl4, SbCl5, and oxygen. Both antimony and chlorine ions became involved in doping and reduced resistivity. The figure of merit suggested that films deposited at 500 °C with the ratio of SnCl4/SbCl5 equals to 0.5 have the best quality. The dopant in the degenerate films narrowed the bandgap because of interaction between electrons and impurities. A mathematical model of the shifting in bandgap is proposed with the consideration of the effective mass of the carriers and well fitted to the experimental results.
Coherency strain enhanced dielectric-temperature property of rare-earth doped BaTiO3
Authors: Jeon Sang-Chae , Kang Suk-Joong L.
Published: March 2013

Core/shell-grained BaTiO3 samples were prepared with addition of rare earth elements. The core/shell interface was semi-coherent, and many misfit dislocations formed in Dy-doped samples. In contrast, a coherent interface and few dislocations were observed in Ho- and Er-doped samples. Dy-doped samples exhibited poor temperature stability, showing a peak with no frequency dispersion. Ho- and Er-doped samples exhibited a broad curve with frequency dispersion. This improved temperature stability is attributed to the coherency strain, which leads to the formation of polar nano-regions in the shell. Coherency at the core/shell interface is critical to improve the temperature stability of core/shell-structured BaTiO3.
Plasmon dispersion in quasi-freestanding graphene on Ni(111)
Authors: Cupolillo A. , Ligato N. , Caputi L. S.
Published: March 2013

The electronic properties of graphene formed on Ni(111) by chemical vapor deposition and intercalated with Cs atoms have been studied by angle-resolved electron-energy-loss spectroscopy. The dispersion curve of π plasmon, in comparison with the analogous dispersion curve obtained in the absence of intercalated Cs, shows that alkali metal atoms make graphene to be quasi-free, with a much lowered charge transfer, and with the recovery of the π band linearity at Dirac points.
Photon- and phonon-assisted tunneling in the three-dimensional charge stability diagram of a triple quantum dot array
Authors: Braakman Floris R. , Barthelemy Pierre , Reichl Christian , Wegscheider Werner , Vandersypen Lieven M. K.
Published: March 2013

We report both photon- and phonon-assisted tunneling transitions in a linear array of three quantum dots, which can only be understood by considering the full three-dimensionality of the charge stability diagram. Such tunneling transitions potentially contribute to leakage of qubits defined in this system. A detailed understanding of these transitions is important as they become more abundant and complex to analyze as quantum dot arrays are scaled up.
Measurement of energetic-particle-driven core magnetic fluctuations and induced fast-ion transport
Authors: Lin L. , Ding W. X. , Brower D. L. , Koliner J. J. , Eilerman S. , Reusch J. A. , Anderson J. K. , Nornberg M. D. , Sarff J. S. , Waksman J. , Liu D.
Published: March 2013

Internal fluctuations arising from energetic-particle-driven instabilities, including both density and radial magnetic field, are measured in a reversed-field-pinch plasma. The fluctuations peak near the core where fast ions reside and shift outward along the major radius as the instability transits from the n = 5 to n = 4 mode. During this transition, strong nonlinear three-wave interaction among multiple modes accompanied by enhanced fast-ion transport is observed.
Thermal effect of plasmon oscillations on the tunnel current in gold nanoisland thin film at low laser intensity
Authors: Yajadda M. M. A. , Ostrikov K.
Published: March 2013

The effect of plasmon oscillations on the DC tunnel current in a gold nanoisland thin film (GNITF) is investigated using low intensity P ∼ 1 W/cm2 continuous wave lasers. While DC voltages (1–150 V) were applied to the GNITF, it was irradiated with lasers at different wavelengths (λ = 473, 532, and 633 nm). Because of plasmon oscillations, the tunnel current increased. It is found that the tunnel current enhancement is mainly due to the thermal effect of plasmon oscillations rather than other plasmonic effects. The results are highly relevant to applications of plasmonic effects in opto-electronic devices.
Flower visitation by honey possums (Tarsipes rostratus) in a coastal banksia heathland infested with the plant pathogen Phytophthora cinnamomi
Authors: Dundas Shannon J. , Fleming Patricia A. , Hardy Giles E. St J.
Published: March 2013

The honey possum (Tarsipes rostratus) is a tiny (7–10 g) obligate nectarivore endemic to south-west Western Australia that relies on high floristic diversity for year-round nectar and pollen resources. We investigated flower visitation by honey possums at a site in the presence of the plant pathogen Phytophthora cinnamomi by sampling pollen on the head of captured and radio-tracked individuals. The aim of the study was to identify plant species that were visited and to compare these with known susceptibility to Phytophthora to assess the potential impact of further spread of the pathogen on honey possums. Nine plant taxa were regularly identified from pollen on honey possums, including four Banksia species. Six of the nine plant taxa identified (Banksia plumosa, Adenanthos cuneatus, Calothamnus gracilis, B. brunnea, B. nutans, B. tenuis) were most frequently visited by honey possums, each making up >20% of pollen grains for at least one season. Five of the nine plant taxa are known to be susceptible to Phytophthora, which substantially changes vegetation composition in its wake. The inevitable spread of Phytophthora is postulated to result in the localised loss of resources for honey possums and is a concern for on-going conservation management.
Standardising the ‘after‐school’ period for children's physical activity and sedentary behaviour
Authors: Arundell Lauren , Salmon Jo , Veitch Jenny , O'Connell Eoin , Hinkley Trina , Hume Clare
Published: March 2013

Issue addressed

Studies examining children's after‐school physical activity (PA) and sedentary behaviours (SB) often use arbitrary times to signify the period start and end. A standardised time is required for future research examining this period. The aim of the present study was to compare children's after‐school behaviour using three definitions of the after‐school period, namely (1) end of school to 6 pm; (2) end of school to dinner time; and (3) end of school to sunset, to determine the extent of variability in PA and SB during the after‐school period depending on the definition used.

Methods

Children (n = 308; aged 8 years) from the Melbourne Transform‐Us! intervention wore an accelerometer and a subsample (n = 112) wore an activPAL inclinometer in 2010. The end of school bell time was obtained from the child's school, parents completed a 2‐day log reporting their child's dinner time and sunset times were obtained from Geoscience Australia. ActiGraph accelerometers assessed the proportion of time spent sedentary (SED) and that spent in light (LPA), moderate (MPA) and moderateto‐vigorous (MVPA) PA during the three time periods; activPAL inclinometers assessed the proportion of time spent sitting (SIT).

Results

Apart from the end of school time (3:30 pm), dinner (range 3:30 pm‐8:40 pm) and sunset (range 5:07 pm‐7:34 pm) times varied. Despite this, there were no significant differences in estimates of the proportions of time children spent in SED, LPA, MPA, MVPA or SIT between the three after‐school periods examined.

Conclusion

Given the small differences in SED, PA and SIT during the after‐school period regardless of the definition (6 pm, sunset or dinner time), it appears that applying a standardised definition of end of school to 6 pm is acceptable for defining children's PA and SB during the after‐school period.

So what?

The use of a standardised after‐school definition (end of school to 6 pm), will enable future studies exploring children's after‐school PA and SB to be more comparable.
Hunk negatively regulates c-myc to promote Akt-mediated cell survival and mammary tumorigenesis induced by loss of
Pten
Authors: Yeh Elizabeth S. , Belka George K. , Vernon Ann E. , Chen Chien-Chung , Jung Jason J. , Chodosh Lewis A.
Published: March 2013

The protooncogenes Akt and c-myc each positively regulate cell growth and proliferation, but have opposing effects on cell survival. These oncogenes cooperate to promote tumorigenesis, in part because the prosurvival effects of Akt offset the proapoptotic effects of c-myc. Akt’s ability to counterbalance c-myc’s proapoptotic effects has primarily been attributed to Akt-induced stimulation of prosurvival pathways that indirectly antagonize the effects of c-myc. We report a more direct mechanism by which Akt modulates the proapoptotic effects of c-myc. Specifically, we demonstrate that Akt up-regulates the adenosine monophosphate-associated kinase (AMPK)-related protein kinase,
H
ormonally
u
p-regulated
n
eu-associated
k
inase (Hunk), which serves as an effector of Akt prosurvival signaling by suppressing c-myc expression in a kinase-dependent manner to levels that are compatible with cell survival. Consequently, Akt pathway activation in the mammary glands of
Hunk

−/−

mice results in induction of c-myc expression to levels that induce apoptosis. c-myc knockdown rescues the increase in apoptosis induced by Hunk deletion in cells in which Akt has been activated, indicating that repression of c-myc is a principal mechanism by which Hunk mediates the prosurvival effects of Akt. Consistent with this mechanism of action, we find that Hunk is required for c-myc suppression and mammary tumorigenesis induced by phosphatase and tensin homolog (
Pten
) deletion in mice. Together, our findings establish a prosurvival function for Hunk in tumorigenesis, define an essential mechanism by which Akt suppresses c-myc–induced apoptosis, and identify Hunk as a previously unrecognized link between the Akt and c-myc oncogenic pathways.
Enterocyte loss of polarity and gut wound healing rely upon the F-actin–severing function of villin
Authors: Ubelmann Florent , Chamaillard Mathias , El-Marjou Fatima , Simon Anthony , Netter Jeanne , Vignjevic Danijela , Nichols Buford L. , Quezada-Calvillo Roberto , Grandjean Teddy , Louvard Daniel , Revenu Céline , Robine Sylvie
Published: March 2013

Significance

Intestinal epithelium damage is common but becomes recurrent in chronic intestinal disorders. Healing implies cell migration, which necessitates extensive cellular reorganization. We demonstrate that intestinal epithelial cells completely disassemble their apical actin-based microvilli upon migration, and we identify the protein villin and its actin-severing function as responsible for this physiological process. We show that this apical pole effacement is required for the acquisition of a motile phenotype and efficient wound healing. These findings demonstrate how intestinal epithelial cells acquired a mechanism at the level of the actin cytoskeleton to convert efficiently from a highly differentiated to a motile polarity.
Atomic structure of the 75 MDa extremophile
Sulfolobus
turreted icosahedral virus determined by CryoEM and X-ray crystallography
Authors: Veesler David , Ng Thiam-Seng , Sendamarai Anoop K. , Eilers Brian J. , Lawrence C. Martin , Lok Shee-Mei , Young Mark J. , Johnson John E. , Fu Chi-yu
Published: March 2013

Sulfolobus
turreted icosahedral virus (STIV) was isolated in acidic hot springs where it infects the archeon
Sulfolobus solfataricus
. We determined the STIV structure using near-atomic resolution electron microscopy and X-ray crystallography allowing tracing of structural polypeptide chains and visualization of transmembrane proteins embedded in the viral membrane. We propose that the vertex complexes orchestrate virion assembly by coordinating interactions of the membrane and various protein components involved. STIV shares the same coat subunit and penton base protein folds as some eukaryotic and bacterial viruses, suggesting that they derive from a common ancestor predating the divergence of the three kingdoms of life. One architectural motif (β-jelly roll fold) forms virtually the entire capsid (distributed in three different gene products), indicating that a single ancestral protein module may have been at the origin of its evolution.
Rhetoric of Doom and Redemption: Reverend Jermain Loguen's Jeremiadic Speech Against the Fugitive Slave Law of 1850
Authors: Minifee Paul
Published: March 2013

In his monumental speech protesting the Fugitive Slave Law of 1850, Rev. Jermain W. Loguen urges his fellow townsmen of Syracuse, NY, an “open city” to fugitives, to defy the new federal legislation by protecting the city's fugitives from federal marshals en route to apprehend them. My analysis of Loguen's speech examines his use of American and African American jeremiadic strategies to convince his audience of primarily white Christian abolitionists that their unified resistance against the new law was part of God's providential plan to redeem the nation of the sin of slavery. My study also reveals how Loguen's appeals to manhood, through associating divine punishment with the emasculation of American men, as well as his establishment of “identification” around shared religious and political values, proved effective in rallying Syracuse's citizens to defend their God-given freedom.
The Stylistic Virtues of Clarity and Obscurity in Augustine of Hippo's De doctrina christiana
Authors: Camper K. Martin
Published: March 2013

In antiquity, rhetorical treatises generally identified clarity and obscurity as positive and negative qualities of style, respectively. But in the fifth century, Augustine developed a valuation such that both clarity and obscurity could potentially function as equally viable resources for persuasion. While previous rhetorical treatises acknowledged that standards of perspicuity varied with genre, Augustine's stipulations for variability are tied much more closely to the particulars of the rhetorical situation. In a bold vision of the potency of style, Augustine demonstrates how a principle like clarity can be adjusted according to the rhetorical situation.
Examples of degenerations of Cohen-Macaulay modules
Authors: Hiramatsu Naoya , Yoshino Yuji
Published: March 2013

We study the degeneration problem for maximal Cohen-Macaulay modules and give several examples of such degenerations. It is proved that such degenerations over an even-dimensional simple hypersurface singularity of type(An)(A_n)are given by extensions. We also prove that all extended degenerations of maximal Cohen-Macaulay modules over a Cohen-Macaulay complete local algebra of finite representation type are obtained by iteration of extended degenerations of Auslander-Reiten sequences.
Impact of Present-on-admission Indicators on Risk-adjusted Hospital Mortality Measurement
Authors: Dalton Jarrod E. , Glance Laurent G. , Mascha Edward J. , Ehrlinger John , Chamoun Nassib , Sessler Daniel I.
Published: March 2013

Background:

Benchmarking performance across hospitals requires proper adjustment for differences in baseline patient and procedural risk. Recently, a Risk Stratification Index was developed from Medicare data, which used all diagnosis and procedure codes associated with each stay, but did not distinguish present-on-admission (POA) diagnoses from hospital-acquired diagnoses. We sought to (1) develop and validate a risk index for in-hospital mortality using only POA diagnoses, principal procedures, and secondary procedures occurring before the date of the principal procedure (POARisk) and (2) compare hospital performance metrics obtained using the POARisk model with those obtained using a similarly derived model which ignored the timing of diagnoses and procedures (AllCodeRisk).

Methods:

We used the 2004–2009 California State Inpatient Database to develop, calibrate, and prospectively test our models (n = 24 million). Elastic net logistic regression was used to estimate the two risk indices. Agreement in hospital performance under the two respective risk models was assessed by comparing observed-to-expected mortality ratios; acceptable agreement was predefined as the AllCodeRisk-based observed-to-expected ratio within ±20% of the POARisk-based observed-to-expected ratio for more than 95% of hospitals.

Results:

After recalibration, goodness of fit (i.e., model calibration) within the 2009 data was excellent for both models. C-statistics were 0.958 and 0.981, respectively, for the POARisk and AllCodeRisk models. The AllCodeRisk-based observed-to-expected ratio was within ±20% of the POARisk-based observed-to-expected ratio for 89% of hospitals, which was slightly lower than the predefined limit of agreement.

Conclusion:

Consideration of POA coding meaningfully improved hospital performance measurement. The POARisk model should be used for risk adjustment when POA data are available.
Predicting Acute Pain after Cesarean Delivery Using Three Simple Questions
Authors: Pan Peter H. , Tonidandel Ashley M. , Aschenbrenner Carol A. , Houle Timothy T. , Harris Lynne C. , Eisenach James C.
Published: March 2013

Background:

Interindividual variability in postoperative pain presents a clinical challenge. Preoperative quantitative sensory testing is useful but time consuming in predicting postoperative pain intensity. The current study was conducted to develop and validate a predictive model of acute postcesarean pain using a simple three-item preoperative questionnaire.

Methods:

A total of 200 women scheduled for elective cesarean delivery under subarachnoid anesthesia were enrolled (192 subjects analyzed). Patients were asked to rate the intensity of loudness of audio tones, their level of anxiety and anticipated pain, and analgesic need from surgery. Postoperatively, patients reported the intensity of evoked pain. Regression analysis was performed to generate a predictive model for pain from these measures. A validation cohort of 151 women was enrolled to test the reliability of the model (131 subjects analyzed).

Results:

Responses from each of the three preoperative questions correlated moderately with 24-h evoked pain intensity (r = 0.24–0.33, P < 0.001). Audio tone rating added uniquely, but minimally, to the model and was not included in the predictive model. The multiple regression analysis yielded a statistically significant model (R
2 = 0.20, P < 0.001), whereas the validation cohort showed reliably a very similar regression line (R
2 = 0.18). In predicting the upper 20th percentile of evoked pain scores, the optimal cut point was 46.9 (z =0.24) such that sensitivity of 0.68 and specificity of 0.67 were as balanced as possible.

Conclusions:

This simple three-item questionnaire is useful to help predict postcesarean evoked pain intensity, and could be applied to further research and clinical application to tailor analgesic therapy to those who need it most.
Anesthesia for In Utero Repair of Myelomeningocele
Authors: Ferschl Marla , Ball Robert , Lee Hanmin , Rollins Mark D.
Published: March 2013

Recently published results suggest that prenatal repair of fetal myelomeningocele is a potentially preferable alternative when compared to postnatal repair. In this article, the pathology of myelomeningocele, unique physiologic considerations, perioperative anesthetic management, and ethical considerations of open fetal surgery for prenatal myelomeningocele repair are discussed. Open fetal surgeries have many unique anesthetic issues such as inducing profound uterine relaxation, vigilance for maternal or fetal blood loss, fetal monitoring, and possible fetal resuscitation. Postoperative management, including the requirement for postoperative tocolysis and maternal analgesia, are also reviewed. The success of intrauterine myelomeningocele repair relies on a well-coordinated multidisciplinary approach. Fetal surgery is an important topic for anesthesiologists to understand, as the number of fetal procedures is likely to increase as new fetal treatment centers are opened across the United States.
Global Health Implications of Preanesthesia Medical Examination for Ophthalmic Surgery
Authors: Phillips Michael B. , Bendel Rick E. , Crook Julia E. , Diehl Nancy N.
Published: March 2013

Background:

Preanesthesia medical examination is a common procedure performed before ophthalmic surgery. The frequency and characteristics of new medical issues and unstable medical conditions revealed by ophthalmic preanesthesia medical examination are unknown. We conducted a prospective observational study to estimate the proportion of patients with new medical issues and unstable medical conditions discovered during ophthalmic preanesthesia medical examination. Secondary aims were to characterize abnormal findings and assess surgical delay and adverse perioperative events, in relation to findings.

Methods:

Patients having preanesthesia medical examination, before ophthalmic surgery, were enrolled over a period of 2 years. A review was conducted of historical, physical examination, and test findings from the preanesthesia medical examination.

Results:

From review of medical records of 530 patients, 100 patients (19%; 95% CI, 16–23%) were reported by providers to have abnormal conditions requiring further medical evaluation. Of these, 12 (12%) had surgery delayed. Retrospective review of examination results identified an additional 114 patients with abnormal findings for a total of 214 (40%; 95% CI, 36–45%) patients. Among the 214 patients, primary findings were cardiovascular (139, 26%), endocrine (26, 5%), and renal (24, 5%). Complications occurred in 49 (9%; 95% CI, 7–12%) patients within 1 month of surgery.

Conclusions:

Ophthalmic preanesthesia medical examination frequently detects new medical issues or unstable existing conditions, which do not typically alter conduct of perioperative procedures or outcomes. However, these conditions are relevant to long-term patient health and should be conveyed to primary care physicians for further evaluation.
Patterns of Preoperative Consultation and Surgical Specialty in an Integrated Healthcare System
Authors: Thilen Stephan R. , Bryson Christopher L. , Reid Robert J. , Wijeysundera Duminda N. , Weaver Edward M. , Treggiari Miriam M.
Published: March 2013

Background:

Many patients scheduled for elective surgery are referred for a preoperative medical consultation. Only limited data are available on factors associated with preoperative consultations. The authors hypothesized that surgical specialty contributes to variation in referrals for preoperative consultations.

Methods:

This is a cohort study using data from Group Health Cooperative, an integrated healthcare system. The authors included 13,673 patients undergoing a variety of common procedures—primarily low-risk surgeries—representing six surgical specialties, in 2005–2006. The authors identified consultations by family physicians, general internists, pulmonologists, or cardiologists in the 42 days preceding surgery. Multivariable logistic regression was used to estimate the association between surgical specialty and consultation, adjusting for potential confounders including the revised cardiac risk index, age, gender, Deyo comorbidity index, number of prescription medications, and 11 medication classes.

Results:

The authors found that 3,063 (22%) of all patients had preoperative consultations, with significant variation by surgical specialty. Patients having ophthalmologic, orthopedic, or urologic surgery were more likely to have consultations compared with those having general surgery—adjusted odds ratios (95% CI) of 3.8 (3.3–4.2), 1.5 (1.3–1.7), and 2.3 (1.8–2.8), respectively. Preoperative consultations were more common in patients with lower revised cardiac risk scores.

Conclusion:

There is substantial practice variation among surgical specialties with regard to the use of preoperative consultations in this integrated healthcare system. Given the large number of consultations provided for patients with low cardiac risk and for patients presenting for low-risk surgeries, their indications, the financial burden, and cost-effectiveness of consultations deserve further study.
Evaluation of Spinal Toxicity and Long-term Spinal Reflex Function after Intrathecal Levobupivaciane in the Neonatal Rat
Authors: Hamurtekin Emre , Fitzsimmons Bethany L. , Shubayev Veronica I. , Grafe Marjorie R. , Deumens Ronald , Yaksh Tony L. , Walker Suellen M.
Published: March 2013

Background:

Neuraxial anesthesia is utilized in children of all ages. Local anesthetics produce dose-dependent toxicity in certain adult models, but the developing spinal cord may also be susceptible to drug-induced apoptosis. In postnatal rodents, we examined the effects of intrathecal levobupivacaine on neuropathology and long-term sensorimotor outcomes.

Methods:

Postnatal day 3 (P3) or P7 rat pups received intrathecal levobupivacaine 2.5 mg/kg (0.5%) or saline. Mechanical withdrawal thresholds and motor block were assessed. Spinal cord tissue analysis included apoptosis counts (activated caspase-3, Fluoro-Jade C) at 24 h, glial reactivity at 7 days, and histopathology in cord and cauda equina at 24 h and 7 days. Long-term spinal function in young adults (P35) was assessed by hind limb withdrawal thresholds, electromyography responses to suprathreshold stimuli, and gait analysis.

Results:

Intrathecal levobupivacaine produced spinal anesthesia at P3 and P7. No increase in apoptosis or histopathological change was seen in the cord or cauda equina. In the P3 saline group, activated caspase-3 (mean ± SEM per lumbar cord section 6.1 ± 0.3) and Fluoro-Jade C (12.1 ± 1.2) counts were higher than at P7, but were not altered by levobupivacaine (P = 0.62 and P = 0.11, two-tailed Mann–Whitney test). At P35, mechanical withdrawal thresholds, thermal withdrawal latency, and electromyographic reflex responses did not differ across P3 or P7 levobupivacaine or saline groups (one way ANOVA with Bonferroni comparisons). Intrathecal bupivacaine at P3 did not alter gait.

Conclusion:

Single dose intrathecal levobupivacaine 0.5% did not increase apoptosis or produce spinal toxicity in neonatal rat pups. This study provides preclinical safety data relevant to neonatal use of neuraxial local anesthesia.
Juvenile Myasthenia Gravis
Authors: Castro Diana , Derisavifard Samir , Anderson Mariam , Greene Medrith , Iannaccone Susan
Published: March 2013

Objective:

Juvenile myasthenia gravis (JMG) is an antibody-mediated autoimmune disorder of the neuromuscular junction, at the postsynaptic end plate. JMG presents with fluctuating skeletal muscle weakness and fatigue before the age of 18 years. Very frequently JMG presents with the involvement of the oculomotor muscles, with or without generalized involvement.

Methods:

We performed a retrospective chart review of patients diagnosed with myasthenia in the pediatric neuromuscular clinics at UT Southwestern, between 1990 and 2010. Osserman classification and the response to therapy scale of Millichap and Dodge were used to compare each patient's severity of myasthenia and responsiveness to drugs before the surgery as a baseline and at the last visit, after thymectomy.

Results:

Fifty-eight patients were included; 29 (50%) were African American, and 34 (58.6%) were female. Age of onset was 11 months to 17 years, and 38 patients (65%) presented as generalized myasthenia gravis. Forty-nine patients (84%) were acetylcholine receptor antibody (AchR-Ab) positive. Of the 32 to undergo thymectomy, 19 subjects (59%) experienced an improved response to B level on the Myasthenia Scale of Millichap and Dodge (good improvement, both objective and subjective, but continuation of drug therapy required in the same or lower dosage) and 75% experienced a drop in Osserman classification by at least 1. Of the 8 individuals who did not show improvement after thymectomy, 4 subjects (50%) underwent repeat thymectomy. They had initially less invasive fluoroscopic or thoracoscopic procedure. Thymic hyperplasia was found in 7 patients (21%) and thymoma in 2.

Conclusions:

Thymectomy was well tolerated by this group of children. There was clinical improvement after thymectomy in two thirds of the AchR-Ab–positive generalized myasthenia gravis patients. Thymic pathology was seen in less than one third of the patients who underwent thymectomy, with thymic hyperplasia being common. Further studies are necessary to determine whether thymectomy is indicated for all children with generalized JMG. More information about the immunologic, genetic, and molecular differences between patients may determine the best treatment for individual patients.
Difference in Central and Peripheral Recovery in a Patient With Severe Axonal Motor Neuropathy and Central Nervous System Involvement and Review of Literature
Authors: Moody Shade’ B. , Wanchoo Ruchi J. , Kalamangalam Giridhar P. , Infante Ernesto , Sheikh Kazim A.
Published: March 2013

In the literature, the term fulminant Guillain–Barré syndrome is used to refer to patients with Guillain–Barré syndrome with rapidly progressive and severe weakness and/or comatose state mimicking brain death. We present the case of a 53-year-old man with fulminant Guillain–Barré syndrome with discrepancy in central nervous system and peripheral nervous system recovery. Our review of literature confirms that these patients often have good and relatively rapid recovery of central nervous system function, whereas peripheral nervous system function is relatively delayed and often incomplete.
EARLY SPONTANEOUS CLOSURE AFTER REOPENING OF A PREVIOUSLY REPAIRED MACULAR HOLE
Authors: Vahdani Kaveh , Park Jonathan C. , Raman Vasant S.
Published: March 2013

Purpose:

To describe a case of early spontaneous closure of macular hole after reopening after previous successful surgical repair.

Methods:

A 72-year-old female patient was treated for stage 2 idiopathic macular hole in the right eye. The hole remained anatomically closed for 2 months postoperatively, before reopening 1 month later.

Results:

The patient was listed for revision surgery; however, on the day of the operation, which was 2 months after the reopening, the hole seemed to have closed spontaneously. Two years later, the macular hole remains closed with best-corrected visual acuity of 6/9.

Conclusion:

Spontaneous closure of macular holes after reopening is a rare phenomenon. The case presented here demonstrates that for early reopening of macular holes, a period of observation with serial optical coherence tomography may allow the hole to close spontaneously before proceeding with further surgical intervention.
SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY OF ROTH SPOTS
Authors: Giovinazzo Jerome , Mrejen Sarah , Freund K. Bailey
Published: March 2013

Purpose:

To describe the retinal findings of subacute bacterial endocarditis, their evolution after treatment, and analysis with spectral-domain optical coherence tomography.

Methods:

Retrospective chart review.

Results:

A 21-year-old man presented with the sudden onset of a central scotoma in his left eye because of a sub–internal limiting membrane hemorrhage overlying the left fovea. When examined 2 weeks later, Roth spots were noted in his right eye. The patient was immediately referred to his internist and diagnosed with subacute bacterial endocarditis with cultures positive for Streptococcus viridans. He subsequently underwent aortic valve replacement surgery after 4 weeks of intravenous antibiotic therapy. When examined 4 weeks after valve replacement surgery, there was regression of the Roth spots.

Conclusion:

The present case demonstrates the importance of a funduscopic examination in the early diagnosis and management of subacute bacterial endocarditis. The analysis of Roth spots with spectral-domain optical coherence tomography suggested that they were septic emboli.
Delayed Small Bowel Transit in Children With Cystic Fibrosis and Pancreatic Insufficiency
Authors: Rovner Alisha J. , Schall Joan I. , Mondick John T. , Zhuang Hongming , Mascarenhas Maria R.
Published: March 2013

Objective:

Gastrointestinal disturbances are common in people with cystic fibrosis (CF); however, motility studies in this population have yielded inconsistent results. This study examined gastric emptying (GE) and small bowel transit (SBT) time in children with CF and pancreatic insufficiency compared with a healthy adult reference group.

Methods:

Participants consumed an 8‐ounce liquid test meal (approximately 550 calories, 32 g of fat) labeled with 300 μCi 99m technetium (Tc) sulfur colloid. Subjects with CF received a standard dose of pancreatic enzymes before consuming the test meal. GE and SBT were measured using a standard nuclear medicine scan. GE was determined after correcting for 99mTc decay in both anterior and posterior images. SBT was determined by following the movement of the tracer from the stomach to the cecum. The percentage arrival of total small bowel activity at the terminal ileum and cecum/ascending colon at 6 hours was used as an index of SBT. A 1‐way analysis of covariance was performed for comparisons between groups after adjustment for age, sex, and body mass index.

Results:

Subjects with CF (n = 16) had similar GE compared with the healthy reference group (n = 12); however, subjects with CF had significantly prolonged SBT time. At 6 hours, 37.2% ± 25.4% (95% CI 23.7–50.7) of the tracer reached the terminal ileum and colon compared with 68.6% ± 13.1% (95% CI 60.2–76.9) for the reference group (P < 0.001). After controlling for sex, age, and body mass index, this difference remained statistically significant (F = 12.06, adjusted R2 = 0.44, P < 0.002).

Conclusions:

Children with CF and pancreatic insufficiency had unaltered GE but delayed SBT time when taking pancreatic enzymes.
A Multidisciplinary Clinical Program Is Effective in Stabilizing BMI and Reducing Transaminase Levels in Pediatric Patients With NAFLD
Authors: DeVore Stephanie , Kohli Rohit , Lake Kathleen , Nicholas Lynda , Dietrich Kim , Balistreri William F. , Xanthakos Stavra A.
Published: March 2013

Background and Aim:

Weight loss is an effective treatment for children with nonalcoholic fatty liver disease (NAFLD), but it is extremely difficult to achieve outside of an intensive weight management program. We hypothesized that one can achieve success in improving NAFLD and weight‐related outcomes in a structured and focused multidisciplinary clinical program feasible to implement in a gastroenterology clinic.

Methods:

We prospectively tracked the clinical status of our patients enrolled in a multidisciplinary program of dietary and exercise advice through an institutional review board–approved NAFLD registry. Each patient met with a gastroenterologist and dietitian every 3 months for 30 minutes to set individualized goals and monitor progress.

Results:

A total of 108 children have been enrolled in the registry, and of the 83 that were eligible for 1‐year follow‐up and included in the analysis, 39 patients returned, resulting in a 47% follow‐up rate. These 39 patients showed statistically significant improvements in mean BMI z score (−0.1 U, P < 0.05), total (−11 mg/dL, P < 0.05) and low‐density lipoprotein (9 mg/dL, P < 0.05) cholesterol, and serum alanine aminotransferase levels (−36 U/L) and aspartate aminotransferase levels (−22 U/L) levels.

Conclusions:

A clinically feasible multidisciplinary program for obese pediatric patients with NAFLD stabilized BMI z score and significantly improved aminotransferase levels at 1‐year follow‐up.
Early Life Exposures as Risk Factors for Pediatric Eosinophilic Esophagitis
Authors: Jensen Elizabeth T. , Kappelman Michael D. , Kim Hannah P. , Ringel‐Kulka Tamar , Dellon Evan S.
Published: March 2013

Objectives:

Few etiologic studies of eosinophilic esophagitis (EoE) have been conducted. Early life exposures have been shown to predispose to other allergic disease, but their role has not been assessed in EoE. The present study sought to explore early life exposures as possible risk factors for developing EoE in the pediatric population.

Methods:

This was a 2‐phase case‐control study conducted at the University of North Carolina. The first phase consisted of survey development for early life exposures via cognitive interview. In the second phase, a telephone‐based questionnaire was administered to cases with EoE (n = 31) and 2 sets of controls, patients with gastroesophageal reflux disease, and siblings of nonsyndromic cleft lip/palate patients (n = 26 in each). Different controls were explored to identify controls reflective of the source population of the cases. Siblings of cleft lip/palate patients were identified as the more suitable control population. Odds ratios were calculated to evaluate the association between early life exposures and the development of pediatric EoE.

Results:

Early life exposures were associated with increased odds of developing pediatric‐onset EoE. Antibiotic use in infancy was associated with 6 times the odds of having EoE (95% confidence interval 1.7–20.8). Cesarean delivery, preterm birth, and formula‐only or mixed (infant formula and breast milk) feeding also have trends toward increased odds for developing EoE.

Conclusions:

A number of early life exposures may be associated with the development of EoE. These are potentially modifiable risk factors that if confirmed would have implications for improved understanding of EoE pathogenesis and disease prevention.
Bone Deficits in Parenteral Nutrition–Dependent Infants and Children With Intestinal Failure Are Attenuated When Accounting for Slower Growth
Authors: Appleman Stephanie S. , Kalkwarf Heidi J. , Dwivedi Alok , Heubi James E.
Published: March 2013

Objective:

The aim of the present study was to determine whether bone mineral content (BMC) and density (BMD) of infants and children with parenteral nutrition (PN)–dependent intestinal failure (IF) is lower than healthy controls, and investigate potential causes of lower BMC and BMD.

Methods:

We performed a cross‐sectional study comparing infants and children with PN‐dependent IF with duos of age‐, sex‐, and race‐matched controls. Lumbar spine BMC and BMD were measured by dual‐energy x‐ray absorptiometry, and serum cytokines, aluminum, insulin‐like growth factor‐1 (IGF‐1), IGF‐binding protein 3 (IGF‐BP3), parathyroid hormone, 25‐hydroxy vitamin D, and 1,25‐dihydroxy vitamin D were measured. Generalized estimating equation models accounting for matching were used for comparisons.

Results:

BMC was 15% and BMD was 12% lower in IF participants than in controls (P ≤ 0.004). Group differences were attenuated to 3% and 7% and were not statistically significant (P = 0.40 and P = 0.07) when adjusted for length and weight; length‐ and weight‐for‐age were lower in IF than in control participants (12.5% vs 63%; 29.5% vs 54%, P ≤ 0.03). IF participants had higher serum aluminum (23 vs 7 μg/L, P < 0.0001), IGF‐1 (97 vs 64 ng/mL, P = 0.04), and 25‐hydroxy vitamin D concentrations (40 vs 30 ng/mL, P = 0.0005), and lower IGF‐BP3 (1418 vs 1812 ng/mL, P < 0.0001) and parathyroid hormone concentrations (51 vs 98 pg/mL, P = 0.0002) than controls. There was no difference in serum cytokine concentrations (P ≥ 0.09).

Conclusions:

Growth retardation is a significant problem for patients with PN‐dependent IF. Additional investigation is needed to elucidate the cause and its effect on bone mass and density, especially the role of IGF‐1 resistance and aluminum toxicity.
Efficacy of Different Probiotic Combinations on Death and Necrotizing Enterocolitis in a Premature Rat Model
Authors: Wu Shu‐Fen , Chiu Hsiao‐Yu , Chen An‐Chyi , Lin Hsiang‐Yu , Lin Hung‐Chih , Caplan Michael
Published: March 2013

Objective:

The aim of the present study was to investigate the most effective probiotic combinations to prevent death and necrotizing enterocolitis (NEC) in a premature rat model.

Methods:

One hundred fifty‐eight premature Sprague‐Dawley premature rats were enrolled. Probiotic strains Bifidobacterium bifidum, B longum, Lactobacillus acidophilus, L plantarum, and B breve were fed as a single strain or mixture with 2 or 3 strains for a total of 9 study groups; control groups received no exogenous probiotic supplement. Fecal samples were collected for 72 hours to detect probiotic strains and pathologic strains by real‐time polymerase chain reaction. Colony counts of probiotic strains Escherichia coli and Klebsiella were compared between groups before and after 36 hours of the study period. The incidence of death and NEC were compared via Fisher exact test between groups.

Results:

The results demonstrated that L plantarum alone (P = 0.0026) and B bifidum with B longum together (P = 0.0017) were more effective in reducing NEC as compared with the control group. All of the study groups except B breve and B bifidum with B breve definitely prevented death compared with controls. B bifidum and B longum together had significantly lower mortality than the control group (P < 0.0001). Colony counts of E coli and Klebsiella in stool samples were significantly decreased in the B bifidum, B longum, and L plantarum group compared with the other study and control groups after 36 hours.

Conclusions:

Administration of a mixture of probiotic strains with B bifidum and B longum was most effective in preventing death and NEC in this animal model, and these observations provide an evidence‐based strategy for designing further neonatal clinical trials.
Absence of Effect of Nasal Continuous Positive Airway Pressure on the Esophageal Phase of Nutritive Swallowing in Newborn Lambs
Authors: Djeddi Djamal , Cantin Danny , Samson Nathalie , Tian Hao , Praud Jean‐Paul
Published: March 2013

Objectives:

It is presently recommended that oral feeding be started in premature infants as soon as possible, often at an age at which nasal continuous positive airway pressure (nCPAP) is still required for ventilatory support. Our previous data showed that application of nCPAP up to 10 cmH2O in full‐term lambs had no deleterious effect on cardiorespiratory safety, feeding efficiency, or on nutritive swallowing–breathing coordination. Besides fear of swallowing–breathing coordination disturbances, esophageal motility disruption by nCPAP could be a reason to delay oral feeding. To our knowledge, no study has focused on the effects of nCPAP on esophageal motility in the neonatal period. The aim of the present study was therefore to further assess the effects of nCPAP on oral feeding by assessing its effects on the esophageal phase of nutritive swallowing (nutritive esophagodeglutition).

Methods:

Six full‐term lambs, ages 2 to 3 days, underwent esophageal multichannel intraluminal impedance‐pH monitoring. Lambs were bottle‐fed under 2 randomized conditions, namely spontaneous breathing and nCPAP 6 cmH2O.

Results:

Beyond confirmation of unaltered feeding efficiency, analysis of multiple variables measured by impedance monitoring revealed that nCPAP 6 does not alter nutritive esophagodeglutition in any way (nCPAP vs spontaneous breathing, P > 0.1 for all variables).

Conclusions:

offering further support to neonatologists pleading for initiation of oral feeding in infants still on nCPAP, the present results set the foundations for similar clinical studies in preterm human infants to confirm the absence of effects of nCPAP on nutritive swallowing.
Diagnosis and follow-up of Bartonella henselae infection in the spleen of an immunocompetent patient by real-time quantitative PCR
Authors: Liberto Maria Carla , Matera Giovanni , Lamberti Angelo G. , Quirino Angela , Barreca Giorgio S. , Marascio Nadia , Baudi Francesco , Caroleo Benedetto , Staltari Orietta , Focà Alfredo
Published: March 2013

Systemic Bartonella henselae infections are unusual in immunocompetent adults. However, here we report one such case of bartonellosis in a 34-year-old patient, who presented with fever and multinodular splenomegaly. We also describe a novel method of identifying Bartonella henselae by real-time quantitative polymerase chain reaction and sequencing of amplified products. This could prevent splenic bartonellosis being mistaken for lymphoma and thereby avert unnecessary splenectomy.