bluuebunny/crossref_metadata_2025 huggingface dataset:
Synaptopodin, a molecule involved in the formation of the dendritic spine apparatus, is a dual actin/α‐actinin binding protein
Authors: Kremerskothen Joachim , Plaas Christian , Kindler Stefan , Frotscher Michael , Barnekow Angelika
Published: January 2005

Synaptopodin (SYNPO) is a cytoskeletal protein that is preferentially located in mature dendritic spines, where it accumulates in the spine neck and closely associates with the spine apparatus. Formation of the spine apparatus critically depends on SYNPO. To further determine its molecular action, we screened for cellular binding partners. Using the yeast two‐hybrid system and biochemical assays, SYNPO was found to associate with both F‐actin and α‐actinin. Ectopic expression of SYNPO in neuronal and non‐neuronal cells induced actin aggregates, thus confirming a cytoplasmic interaction with the actin cytoskeleton. Whereas F‐actin association is mediated by a central SYNPO motif, binding to α‐actinin requires the C‐terminal domain. Notably, the α‐actinin binding domain is also essential for dendritic targeting and postsynaptic accumulation of SYNPO in primary neurons. Taken together, our data suggest that dendritic spine accumulation of SYNPO critically depends on its interaction with postsynaptic α‐actinin and that SYNPO may regulate spine morphology, motility and function via its distinct modes of association with the actin cytoskeleton.
Age‐dependent sensitivity of the developing brain to irradiation is correlated with the number and vulnerability of progenitor cells
Authors: Fukuda Aya , Fukuda Hirotsugu , Swanpalmer Janos , Hertzman Sven , Lannering Birgitta , Marky Ildiko , Björk‐Eriksson Thomas , Blomgren Klas
Published: January 2005

In a newly established model of unilateral, irradiation (IR)‐induced injury we compared the outcome after IR to the immature and juvenile brain, using rats at postnatal days 9 or 23, respectively. We demonstrate that (i) the immature brains contained more progenitors in the subventricular zone (SVZ) and subgranular zone (SGZ) compared with the juvenile brains; (ii) cellular injury, as judged by activation of caspase 3 and p53, as well as nitrotyrosine formation, was more pronounced in the SVZ and SGZ in the immature brains 6 h after IR; (iii) the number of progenitor and immature cells in the SVZ and SGZ decreased 6 h and 7 days post‐IR, corresponding to acute and subacute effects in humans, respectively, these effects were more pronounced in immature brains; (iv) myelination was impaired after IR at both ages, and much more pronounced after IR to immature brains; (v) the IR‐induced changes remained significant for at least 10 weeks, corresponding to late effects in humans, and were most pronounced after IR to immature brains. It appears that IR induces both an acute loss of progenitors through apoptosis and a perturbed microenvironment incompatible with normal proliferation and differentiation, and that this is more pronounced in the immature brain.
β‐Site APP cleaving enzyme up‐regulation induced by 4‐hydroxynonenal is mediated by stress‐activated protein kinases pathways
Authors: Tamagno Elena , Parola Maurizio , Bardini Paola , Piccini Alessandra , Borghi Roberta , Guglielmotto Michela , Santoro Gianni , Davit Annalisa , Danni Oliviero , Smith M. A. , Perry G. , Tabaton Massimo
Published: January 2005

4‐Hydroxynonenal (HNE), an aldehydic product of lipid peroxidation, up‐regulates expression of the β‐site APP cleaving enzyme (BACE‐1), an aspartyl protease responsible for the β‐secretase cleavage of amyloid precursor protein (AβPP), and results in increased levels of amyloid β (Aβ) peptide. The mechanisms underlying this remain unclear but are of fundamental importance because prevention of BACE‐1 up‐regulation is viewed as an important therapeutic strategy. In this study, we exposed NT2 neurons to a range of HNE concentrations (0.5–5 µm) that elicited an up‐regulation of BACE‐1 expression, a significant increase in intracellular and secreted levels of Aβ peptides as well as apoptosis involving poly‐ADP ribose polymerase cleavage and activation of caspase 3. To delineate the molecular events involved in HNE‐mediated BACE‐1 activation, we investigated the involvement of stress‐activated protein kinases (SAPK), signal transducers and activators of transcription (STAT) and serine–threonine kinase B/phosphatidylinositol phosphate 3 kinase (Akt/PtdIns3K). Using specific pharmacological inhibitors, our results show that activation of c‐Jun N‐terminal kinases and p38MAPK., but not STAT or Akt/PtdIns3K, pathways mediate the HNE‐dependent up‐regulation of BACE‐1 expression. Therefore, HNE, an oxidative stress mediator detected in vivo in the brains of Alzheimer's disease patients, may play a pathogenetic role in Alzheimer's disease by selectively activating SAPK pathways and BACE‐1 that regulate the proteolytic processing of AβPP.
Depression in Epilepsy: A Neurobiologic Perspective
Authors: Kanner Andres M.
Published: January 2005

Depression is the most frequent psychiatric comorbidity in patients with epilepsy. By the same token, patients with depression are at higher risk of developing epilepsy than are controls. Such bidirectional relations raise the question of whether both disorders share common pathogenic mechanisms, presenting with common neurotransmitter abnormalities and involvement of the same neuroanatomic structures. In this article, some of the available data in support of this hypothesis are reviewed.
A Modeling Framework for Supply Chain Simulation: Opportunities for Improved Decision Making*
Authors: Van Der Zee D. J. , Van Der Vorst J. G. A. J.
Published: January 2005

Owing to its inherent modeling flexibility, simulation is often regarded as the proper means for supporting decision making on supply chain design. The ultimate success of supply chain simulation, however, is determined by a combination of the analyst's skills, the chain members' involvement, and the modeling capabilities of the simulation tool. This combination should provide the basis for a realistic simulation model, which is both transparent and complete. The need for transparency is especially strong for supply chains as they involve (semi)autonomous parties each having their own objectives. Mutual trust and model effectiveness are strongly influenced by the degree of completeness of each party's insight into the key decision variables. Ideally, visual interactive simulation models present an important communicative means for realizing the required overview and insight. Unfortunately, most models strongly focus on physical transactions, leaving key decision variables implicit for some or all of the parties involved. This especially applies to control structures, that is, the managers or systems responsible for control, their activities and their mutual attuning of these activities. Control elements are, for example, dispersed over the model, are not visualized, or form part of the time‐indexed scheduling of events. In this article, we propose an alternative approach that explicitly addresses the modeling of control structures. First, we will conduct a literature survey with the aim of listing simulation model qualities essential for supporting successful decision making on supply chain design. Next, we use this insight to define an object‐oriented modeling framework that facilitates supply chain simulation in a more realistic manner. This framework is meant to contribute to improved decision making in terms of recognizing and understanding opportunities for improved supply chain design. Finally, the use of the framework is illustrated by a case example concerning a supply chain for chilled salads.
Applying Process Knowledge for Yield Variation Reduction: A Longitudinal Field Study*
Authors: Field Joy M. , Sinha Kingshuk K.
Published: January 2005

The widespread recognition of the detrimental effects of high yield variation in advanced manufacturing technology settings, both in terms of cost and management of production processes, underscores the need to develop effective strategies for reducing yield variation. In this article, we report the findings of a longitudinal field study in an electromechanical motor assembly plant where we examined how the application of process knowledge by production work teams can reduce yield variation. We propose and provide an operationalizion of a strategy to identify the sequence of particular types of actions—actions to control the mean followed by actions to control the variance—that work teams should pursue over time to apply process knowledge for reducing yield variation. The results of our empirical analysis show that yield variation was significantly reduced on three of the four production lines at the manufacturing plant that served as our research site. Differences in strategies for applying process knowledge help explain the different results on each of the production lines.
Diagnosis of Ventricular Aneurysm and Other Severe Segmental Left Ventricular Dysfunction Consequent to a Myocardial Infarction in the Presence of Right Bundle Branch Block: ECG Correlates of a Positive Diagnosis Made via Echocardiography and/or Contrast Ventriculography
Authors: Madias John E. , Ashtiani Ramin , Agarwal Himanshu , Narayan Virenjan K. , Win Moethu , Sinha Anjan
Published: January 2005

Background: A diagnostic ECG sign of a ventricular aneurysm (VA) consequent to a myocardial infarction (MI) in the presence of complete left bundle branch block was recently described, and consists of the presence of ST‐segment elevation (+ST), instead of the expected ST‐segment depression (−ST), in leads V4–6. Generally, complete right bundle branch block (RBBB) is associated with −ST in ECG leads V1–3. We hypothesized that stable +ST, instead of the expected −ST in leads V1–3 in patients with RBBB could be also diagnostic of a VA and other severe segmental left ventricular dysfunction (VA/SSD). Thus, this study was performed to explore the feasibility of using the ECG to diagnose a VA/SSD in the presence of RBBB, and to evaluate the determinants of such diagnosis.

Methods: The frequency of +ST ≥1 mm in leads V1–3 was assessed in patients with RBBB, prior MI, and a VA/SSD diagnosed by echocardiography and/or contrast left cine‐ventriculography. The ECG correlates for a positive or negative diagnosis of a VA/SSD were explored.

Results: Out of 4197 files of our cohort of the Cardiology Clinic, RBBB was detected in 175 patients. Of these, 28 had an old MI, and had a VA/SSD diagnosed by ≥1 of noninvasive and/or invasive non‐ECG tests. Twenty‐one of these 28 patients had stable +ST in ≥1 of leads V1–3 (Group 1), and 7 did not (Group 2). Thus, the sensitivity of this ECG criterion for the diagnosis of VA/SSD was 75%, and the specificity was 100% in this highly selective group. VA/SSD in the septal and anterior myocardial regions was more frequent in the patients of Group 1, than in the patients of Group 2 (P = 0.03 and 0.02, correspondingly). The number of myocardial territories involved with the VA/SSD, or the ejection fraction were not different in the two groups (P = 0.65 and 0.55, correspondingly).

Conclusion: VA/SSD can be diagnosed in the presence of RBBB by the concordant to the QRS repolarization changes (+ST) in leads V1–3. Positivity of this ECG marker for VA/SSD correlates with involvement of the septal or anterior myocardial regions, and represents mechanistically a superimposition of primary repolarization alterations, overcoming the secondary such changes.
Assessment of the Stability of the Individual‐Based Correction of QT Interval for Heart Rate
Authors: Couderc Jean‐Philippe , Xiaojuan Xia , Zareba Wojciech , Moss Arthur J.
Published: January 2005

Background: Modeling the relationship between QT intervals and previous R‐R values remains a challenge of modern quantitative electrocardiography. The technique based on an individual regression model computed from a set of QT–R‐R measurements is presented as a promising alternative. However, a large set of QT–R‐R measurements is not always available in clinical trials and there is no study that has investigated the minimum number of QT–R‐R measurements needed to obtain a reliable individual QT–R‐R model. In this study, we propose guidelines to ensure appropriate use of the regression technique for heart rate correction of QT intervals.

Method: Holter recordings from 205 healthy subjects were included in the study. QT–R‐R relationships were modeled using both linear and parabolic regression techniques. Using a bootstrapping technique, we computed the stability of the individual correction models as a function of the number of measurements, the range of heart rate, and the variance of R‐R values.

Results: The results show that the stability of QT–R‐R individual models was dependent on three factors: the number of measurements included in its design, the heart‐rate range used to design the model, and the T‐wave amplitude. Practically our results showed that a set of 400 QT–R‐R measurements with R‐R values ranging from 600 to 1000 ms ensure a stable and reliable individual correction model if the amplitude of the T wave is at least 0.3 mV. Reducing the range of heart rate or the number of measurements may significantly impact the correction model.

Conclusion: We demonstrated that a large number of QT–R‐R measurements (∼400) is required to ensure reliable individual correction of QT intervals for heart rate.
Effect of Reperfusion on P‐Wave Duration and P‐Wave Dispersion in Acute Myocardial Infarction: Primary Angioplasty versus Thrombolytic Therapy
Authors: Akdemir Ramazan , Ozhan Hakan , Gunduz Huseyin , Tamer Ali , Yazici Mehmet , Erbilen Enver , Albayrak Sinan , Bulur Serkan , Uyan Cihangir
Published: January 2005

Background: Atrial fibrillation (AF) is a common arrhythmia occurring in about 10–20% of patients with acute myocardial infarction (AMI). P‐wave dispersion (PWd) and P‐wave duration (PWD) have been used to evaluate the discontinuous propagation of sinus impulse and the prolongation of atrial conduction time, respectively. This study was conducted to compare the effects of reperfusion either by thrombolytic therapy or primary angioplasty on P‐wave duration and dispersion in patients with acute anterior wall myocardial infarction.

Methods: We have evaluated 72 consecutive patients retrospectively (24 women, 48 men; aged 58 ± 12 years) experiencing acute anterior wall myocardial infarction (AMI) for the first time. Patients were grouped according to the reperfusion therapy received (primary angioplasty (PTCA) versus thrombolytic therapy). Left atrial diameter and left ventricular ejection fraction (LVEF) were determined by echocardiography in all patients. Electrocardiography was recorded from all patients on admission and every day during hospitalization. Maximum (P max) and minimum (P min) P‐wave durations and P‐wave dispersions were calculated before and after the treatment.

Results: There were not any significant differences between the groups regarding age, gender, left ventricular ejection fraction, left atrial diameter and volume, cardiovascular risk factors, and duration from symptom onset to treatment. P‐wave dispersions and P‐wave durations were significantly decreased after PTCA [Mean P max was 113 ± 11 ms before and 95 ± 17 ms after the treatment (P = 0.007)]. Mean PWd was 46 ± 12 ms before and 29 ± 10 ms after the treatment (P = 0.001). Also, P max and PWd were significantly lower in PTCA group (for P max 97 ± 22 ms vs 114 ± 16 ms and for PWd 31 ± 13 ms vs 55 ± 5 ms, respectively).

Conclusions: Primary angioplasty reduces the incidence of AF by decreasing P max and P‐wave dispersion.
Exercise‐Induced Ventricular Arrhythmias and Cardiovascular Death
Authors: Beckerman James , Mathur Anima , Stahr Stephen , Myers Jonathan , Chun Sung , Froelicher Victor
Published: January 2005

Background: Exercise‐induced ventricular arrhythmias (EIVA) are frequently observed during exercise testing. However, the clinical guidelines do not specify their significance and so we examined this issue in our population.

Methods: A retrospective analysis of prospectively collected data was performed on 5754 consecutive male veterans referred for exercise testing at two university‐affiliated Veterans Affairs Medical Centers. Exercise test responses were recorded and cardiovascular mortality was assessed after a mean follow‐up of 6 ± 4 years. EIVA were defined as frequent premature ventricular complexes (PVCs) constituting more than 10% of all ventricular depolarizations during any 30‐second ECG recording, or a run of three or more consecutive PVCs during the exercise test or recovery.

Results: EIVA occurred in 426 patients (7.4%). There were 550 (10.6%) cardiovascular deaths during follow‐up. Seventy two (17%) patients with EIVA died of cardiovascular causes, whereas 478 (9.0%) of patients without EIVA died of cardiovascular causes (P < 0.001). Patients with EIVA had a higher prevalence of cardiovascular disease, resting PVCs, resting ST depression, and ischemia during exercise than patients without EIVA. In a Cox hazards model adjusted for age, cardiovascular disease, exercise‐induced ischemia, ECG abnormalities, exercise capacity and risk factors, EIVA was significantly associated with time to cardiovascular death. The combination of both resting PVCs and EIVA was associated with the highest hazard ratio.

Conclusions: EIVA are independent predictors of cardiovascular mortality after adjusting for other clinical and exercise test variables; combination with resting PVCs carries the highest risk.
Prognostic Value of Head‐Up Tilt Test with Intravenous Beta‐Blocker Administration in Assessing the Efficacy of Therapy in Patients with Vasovagal Syncope
Authors: Gielerak Grzegorz , Makowski Karol , Cholewa Marian
Published: January 2005

Background: Although beta‐blockers are frequently used in order to prevent the recurrence of vasovagal syncope, the efficacy of this treatment is difficult to determine.

Objectives: To determine if the result of a tilt test with an intravenously administered beta‐blocker can predict the long‐term efficacy of beta‐blockade.

Methods: The study group consisted of 62 patients (29 females, mean age 32.8 ± 12.3 years and 33 males, mean age 35.9 ± 18.2 years) with at least two syncopal episodes during 6 months preceding the positive tilt test. After the baseline tilt test, propranolol (0.1 mg/kg BW) was administered intravenously and the tilt test was repeated. Beta‐blockade was considered effective if the subsequent tilt test proved negative (complete efficacy) or if the time until the occurrence of syncope at the subsequent tilt test was longer compared to the baseline test (partial efficacy). All the patients were put on continuous propranolol treatment and were followed up for a period of 1 year or until the time when syncope recurred.

Results: Intravenously administered propranolol prevented (n = 33) or delayed (n = 18) the occurrence of syncope at the tilt test in 51 patients (82%), while it was found ineffective in the remaining 11 patients (18%). During the 8.6 ± 6.7 months (range 1–14) of the follow‐up period, the syncope recurred in 20 patients (32%), with 13 patients (25%) in the group where intravenously administered propranolol proved effective versus 7 patients (64%) for whom intravenously administered propranolol did not prevent syncope during the tilt test (P < 0.015). The survival analysis with respect to the recurrence of syncope revealed a significant correlation between the results of the tilt test with intravenously administered propranolol and the efficacy of the long‐term beta‐blocker therapy (P < 0.003). There were no significant differences with respect to the predictive value of the tilt test with propranolol between the patients showing complete and partial propranolol efficacy (ns), while significant differences were observed between these two groups on one hand and the patients in whom intravenously administered propranolol was found ineffective on the other (P < 0.04 and P < 0.002, respectively).

Conclusions: Intravenous propranolol prevents tilt‐induced syncope in a significant percentage of patients. The results of the tilt tests combined with the administration of propranolol predict the efficacy of a continuous propranolol treatment. Both complete and partial propranolol efficacy at tilt test can successfully identify those patients who will benefit from continuous beta blockade.
Challenges Facing Validation of Noninvasive Electrical Imaging of the Heart
Authors: Nash Martyn P. , Pullan Andrew J.
Published: January 2005

Noninvasive imaging of regional cardiac electrophysiology remains an elusive target. Such imaging is still in its infancy, particularly in comparison to structural imaging modalities such as magnetic resonance imaging (MRI), x‐ray computed tomography (CT), and ultrasound. We present an overview of noninvasive ECG imaging, and the challenges and successes of the various techniques across a range of applications. Unlike MRI and CT, reconstructing cardiac electrophysiology from remote body surface measurements is a highly ill‐posed problem. We therefore first review the theoretical considerations and associated algorithms that are used to address this issue. We then focus on the important issue of validation, and review and contrast recent advances in this area. Efforts to validate ECG inverse procedures using a modeling‐based approach are addressed first. We then discuss various experimental studies that have been conducted to provide appropriate data for robust validations. We present new data that are simultaneously recorded from dense arrays of electrodes on the epicardium and body surface of anesthetized pigs during sinus rhythm, ventricular pacing, and regional ischemia. These data have been obtained specifically to help validate inverse ECG procedures, and form a useful supplement to recent clinical validation studies. Finally, clinical applications and outstanding issues regarding noninvasive imaging of regional cardiac electrophysiology are addressed.
Heart Rate Turbulence: A New Predictor for Risk of Sudden Cardiac Death
Authors: Francis Johnson , Watanabe Mari A. , Schmidt Georg
Published: January 2005

Initial acceleration and a subsequent deceleration of sinus rhythm following a ventricular ectopic beat with a compensatory pause has been termed heart rate turbulence (HRT). The changes in sinus rhythm are thought to be mediated by a baroreflex response to the lower stroke volume of the ectopic beat. HRT is vagally mediated and abolished by atropine, whereas β‐blockers have no effect. HRT has been shown to be an independent and powerful predictor of mortality after myocardial infarction. In patients on β‐blockers, it scores better than left ventricular ejection fraction (LVEF) in its predictive value. Two common measures of HRT are turbulence onset and turbulence slope. When both these measures are abnormal, it is as powerful a predictor of mortality as LVEF. HRT correlates with other indices of cardiac autonomic functions like baroreflex sensitivity and heart rate variability. A composite autonomic index including all these three has been shown to be a powerful predictor of mortality. In patients undergoing direct percutaneous intervention for myocardial infarction, HRT improves in those attaining successful reperfusion. Abnormal values for HRT have been noted in patients with dilated cardiomyopathy and Chagas disease. Diabetic and elderly individuals are more likely to have blunted HRT. HRT cannot be measured in patients lacking ventricular ectopic beats and in patients presenting with atrial fibrillation.
Characteristics of Ti–Si–N coatings on geometrically complex-shaped surface
Authors: Ma Qingsong , Ma Shengli , Xu Kewei
Published: January 2005

Ti–Si–N coatings were successfully deposited by pulsed-direct current plasma-enhanced chemical vapor deposition technique on the surface of high-speed steel substrate, which were bolted to deep blind-hole or U-shaped slice to simulate the complex-shaped surface of various tools and dies, were investigated in this work. The micrographs show that the surface morphologies of the coatings become smoother with an increase of the depth of the bottom of holes or narrow ditches. And the silicon content also increases in Ti–Si–N coatings, which are made of crystallite-phase TiN and amorphous Si3N4 in all cases. The thickness and hardness of the coatings decrease with the increase of the measured depths, which may result from the changes of the composition in the coatings, while the load-bearing capacity of the coatings in the indentation test increase for the coatings prepared on the bottom of holes.
Study on the superhardness mechanism of Ti–Si–N nanocomposite films: Influence of the thickness of the Si3N4 interfacial phase
Authors: Hu Xiaoping , Zhang Huijuan , Dai Jiawei , Li Geyang , Gu Mingyuan
Published: January 2005

The superhardness effect of Ti–Si–N nanocomposite films is closely related to the thickness of the interfacial phase, Si3N4. The influence of the thickness of Si3N4 on the growth structure and mechanical properties of Ti–Si–N nanocomposite films was determined by studying TiN∕Si3N4 multilayers with different thicknesses of Si3N4 layers to reveal the strengthening mechanism of the nanocomposite films. The results show that Si3N4, which is amorphous in single film, can exist as a crystalline structure in TiN∕Si3N4 multilayers when the thickness of the Si3N4 layers is less than 0.7nm because of the “template effect” of TiN. As a result, TiN and Si3N4 layers form a coherent epitaxial growth with a preferred orientation. As a result, the multilayers exhibit a superhardness effect. When the thickness is greater than 0.7nm, Si3N4 exists as an amorphous structure and prevents TiN from coherent epitaxial growth with it, resulting in the decrease of the hardness and elastic moduli of the multilayers. The experiments reveal that when the thickness is less than 0.7nm, the Si3N4 interfacial phase in Ti–Si–N nanocomposite films may have the same structure as that in TiN∕Si3N4 multilayers. The strengthening mechanism of Ti–Si–N nanocomposite films may be the same as that of TiN∕Si3N4 nanomultilayers formed by the coherent epitaxial growth of two layers with different moduli.
Dynamic control of substrate bias for highly c-axis textured thin ferromagnetic CoCrTa film in inductively coupled plasma-assisted sputtering
Authors: Okimura Kunio , Oyanagi Junya
Published: January 2005

This study shows highly c-axis textured thin ferromagnetic Co-based alloy (CoCrTa) film growth in inductively coupled plasma (ICP)-assisted sputtering with an internal coil with an insulated surface. Dynamic control of the substrate bias achieved highly c-axis textured CoCrTa film with a thickness of 70nm in 3min depositions on a Si substrate. The prepared film showed a smooth, dense surface consisting of small crystal grains. The film had a perpendicular magnetic coercivity of 1030Oe and coercive squareness of 0.36. ICP-assisted sputtering with an internal coil with an insulated surface enabled higher-density (⩾1.0×1011cm−3) plasma with lower space potential (⩽30V) compared to ICP-assisted sputtering with bare coil systems. Therefore, the proposed bias control is quite effective for textured growth of thinner Co layers via the effect of a high flux of ions with proper energies. This method can be a candidate for the deposition technique of c-axis textured films as perpendicular magnetic recording media.
Preparation and characterization of atomically clean, stoichiometric surfaces of AIN(0001)
Authors: Mecouch W. J. , Wagner B. P. , Reitmeier Z. J. , Davis R. F. , Pandarinath C. , Rodriguez B. J. , Nemanich R. J.
Published: January 2005

In situ exposure of the (0001) surface of AlN thin films to flowing ammonia at 1120 °C and 10−4Torr removes oxygen∕hydroxide and hydrocarbon species below the detectable limits of x-ray photoelectron spectroscopy and decreases the Al∕N ratio from 1.3 to 1.0. The positions of the Al2p and the N1s core level peaks acquired from the cleaned surfaces were 75.0±0.1eV and 398.2±0.1eV, respectively, which were similar to the values determined for the as-loaded samples. The cleaning process left unchanged the (1×1) low energy electron diffraction pattern, the step-and-terrace microstructure, and the root mean square roughness values observed for the surfaces of the as-loaded samples; i.e., the surface structure and microstructure were not changed by the high-temperature exposure to ammonia at low pressures. Vacuum annealing under 10−7Torr at 1175 °C for 15 min removed all detectable hydrocarbons; however, it did not remove the oxygen∕hydroxide species.
Surface roughness in XeF2 etching of a-Si∕c-Si(100)
Authors: Stevens A. A. E. , Beijerinck H. C. W.
Published: January 2005

Single wavelength ellipsometry and atomic force microscopy (AFM) have been applied in a well-calibrated beam-etching experiment to characterize the dynamics of surface roughening induced by chemical etching of a ∼12nm amorphous silicon (a-Si) top layer and the underlying crystalline silicon (c-Si) bulk. In both the initial and final phase of etching, where either only a-Si or only c-Si is exposed to the XeF2 flux, we observe a similar evolution of the surface roughness as a function of the XeF2 dose proportional to D(XeF2)β with β≈0.2. In the transition region from the pure amorphous to the pure crystalline silicon layer, we observe a strong anomalous increase of the surface roughness proportional to D(XeF2)β with β≈1.5. Not only the growth rate of the roughness increases sharply in this phase, also the surface morphology temporarily changes to a structure that suggests a cusplike shape. Both features suggest that the remaining a-Si patches on the surface act effectively as a capping layer which causes the growth of deep trenches in the c-Si. The ellipsometry data on the roughness are corroborated by the AFM results, by equating the thickness of the rough layer to 6σ, with σ the root-mean-square variation of the AFM’s distribution function of height differences. In the AFM data, the anomalous behavior is reflected in a too small value of σ which again suggests narrow and deep surface features that cannot be tracked by the AFM tip. The final phase morphology is characterized by an effective increase in surface area by a factor of two, as derived from a simple bilayer model of the reaction layer, using the experimental etch rate as input. We obtain a local reaction layer thickness of 1.5 monolayer consistent with the 1.7ML value of Lo et al. [Lo et al., Phys. Rev. B 47, 648 (1993)] that is also independent of surface roughness.
Effects of arrival rate and gas pressure on the chemical bonding and composition in titanium nitride films prepared on Si(100) substrates by ion beam and vapor deposition
Authors: Matsuoka M. , Isotani S. , Mittani J. C. R. , Chubaci J. F. D. , Ogata K. , Kuratani N.
Published: January 2005

Thin titanium nitride films were prepared at room temperature by titanium metal vapor deposition on silicon substrates with simultaneous irradiation by a 2 keV nitrogen ion beam. Arrival rate ratios, ARR(N/Ti), defined as the ratio of the flux of incident atomic nitrogen particles in the ion beam relative to the flux of titanium atoms transported to the substrate, ranged from 0.17 to 2.5. The gas pressure in the vacuum chamber was maintained at 1.3×10−3 or 6.7×10−3Pa during the deposition and irradiation process. Analyses of Ti 2p x-ray photoelectron spectroscopy spectra indicated the presence of metal Ti0, nitride TiN, oxide TiO2, oxynitride TiNxOy, and carbide TiC phases. The Ti0 phase was observed exclusively and predominantly in the films prepared at 1.3×10−3Pa and ARR(N∕Ti)=0.17, 0.21, and 0.28, and the TiN phase is major in the others, as confirmed by the x-ray diffractometry analyses. The chemical composition ratio N/Ti in the films prepared at 1.3×10−3Pa increased linearly with increasing ARR(N/Ti) up to ARR(N∕Ti)=0.42 and tended to be constant with further increase in ARR(N/Ti), while this ratio in the films prepared at 6.7×10−3Pa was almost constant independently of ARR(N/Ti), similar to the constant value observed at 1.3×10−3Pa and higher ARR(N/Ti). This dependence may be understood by comparison with the flux of evaporated titanium atoms, the flux of nitrogen in the beam, and the impingement rate of nitrogen gas in the vacuum chamber, evaluated through the kinetic theory of gases. On the other hand, titanium is known to be one of the chemically active materials which form stable compounds with gases by chemisorption, this fact leading to considerable incorporation of contaminant oxygen and carbon in the depositing titanium film.
Effect of ultrahigh vacuum on ordering temperature, crystallographic and magnetic properties of L1 FePt (001) film on a CrRu underlayer
Authors: Chen J. S. , Lim B. C. , Zhou T. J.
Published: January 2005

The effect of ultrahigh vacuum on ordering temperature, crystallographic and magnetic properties of L10 FePt (001) film grown on a CrRu underlayer were investigated. The base pressure was adjusted by initially flushing with 99.99% purity nitrogen gas in vacuum system. The residual nitrogen gas in the deposition chamber causes the increase in the ordering temperature and the formation of face-centered-cubic-phase FePt grains in the films. Furthermore, the residual gas deteriorates the FePt (001) texture. Large uniaxial anisotropy constant Ku⩾1×107erg∕cm3, and good magnetic squareness (∼1) were obtained at the temperature of Ts⩾250°C when the base pressure is 3×10−8Torr.
A simple physical derivation of Child–Langmuir space-charge-limited emission using vacuum capacitance
Authors: Umstattd R. J. , Carr C. G. , Frenzen C. L. , Luginsland J. W. , Lau Y. Y.
Published: January 2005

The fundamental Child–Langmuir limit on the maximum current density in a vacuum between two infinite parallel electrodes is one of the most well known and often applied rules of plasma physics. We develop a simple model using vacuum capacitance, conservation of energy, and conservation of charge to derive the Child–Langmuir space-charge-limited emission. This capacitive model provides physical insight into the origins of the well known (voltage)3/2/(gap distance)2 scaling of the classical current density and does not require the solution of the nonlinear differential equation normally associated with the Child–Langmuir formulation. In addition, the full spacecharge-limited solution is reproduced without imposing the condition that the electric field be driven to zero at the cathode surface.
The physics of now
Authors: Hartle James B.
Published: January 2005

The world is four-dimensional according to fundamental physics, governed by basic laws that operate in a spacetime that has no unique division into space and time. Yet our subjective experience is divided into present, past, and future. This paper discusses the origin of this division in terms of simple models of information gathering and utilizing systems (IGUSs). Past, present, and future are not properties of four-dimensional spacetime, but notions describing how individual IGUSs process information. Their origin is to be found in how these IGUSs evolved or were constructed. The past, present, and future of an IGUS is consistent with the four-dimensional laws of physics and can be described in four-dimensional terms. The present, for instance, is not a moment of time in the sense of a spacelike surface in spacetime. Rather, there is a localized notion of present at each point along an IGUS’ world line. The common present of many localized IGUSs is an approximate notion appropriate when they are sufficiently close to each other and have relative velocities much less than that of light. But modes of organization that are different from present, past, and future can be imagined that are consistent with the physical laws. We speculate why the present, past, and future organization might be favored by evolution and be therefore, a cognitive universal.
The First Glacial Maximum in North America
Authors: Balco Greg , Rovey Charles W. , Stone John O. H.
Published: January 2005

Despite marine evidence for at least 50 Pliocene-Pleistocene ice sheet advances, only the most recent one has been accurately reconstructed from terrestrial evidence, because there are few techniques for dating older glacial deposits. Here we show that the cosmic ray–produced nuclides beryllium-10 and aluminum-26 can be used to date tills that overlie paleosols.
A Stable Aminyl Radical Metal Complex
Authors: Büttner Torsten , Geier Jens , Frison Gilles , Harmer Jeffrey , Calle Carlos , Schweiger Arthur , Schönberg Hartmut , Grützmacher Hansjörg
Published: January 2005

Metal-stabilized phenoxyl radicals appear to be important intermediates in a variety of enzymatic oxidations. We report that transition metal coordination also supports an aminyl radical, resulting in a stable crystalline complex: [Rh(I)(trop
2
N
.
)(bipy)]
+
OTf
–
(where trop is 5-H-dibenzo[a,d]cycloheptene-5-yl, bipy is 2,2′-bipyridyl, OTf
–
is trifluorosulfonate). It is accessible under mild conditions by one-electron oxidation of the amide complex [Rh(I)(trop
2
N)(bipy)], at a potential of –0.55 volt versus ferrocene/ferrocenium. Both electron paramagnetic resonance spectroscopy and density functional theory support 57% localization of the unpaired spin at N. In reactions with H-atom donors, the Rh-coordinated aminyl behaves as a nucleophilic radical.
An Astronomical 2175 Å Feature in Interplanetary Dust Particles
Authors: Bradley John , Dai Zu Rong , Erni Rolf , Browning Nigel , Graham Giles , Weber Peter , Smith Julie , Hutcheon Ian , Ishii Hope , Bajt Sasa , Floss Christine , Stadermann Frank , Sandford Scott
Published: January 2005

The 2175 angstrom extinction feature is the strongest (visible-ultraviolet) spectral signature of dust in the interstellar medium. Forty years after its discovery, the origin of the feature and the nature of the carrier(s) remain controversial. Using a transmission electron microscope, we detected a 5.7–electron volt (2175 angstrom) feature in interstellar grains embedded within interplanetary dust particles (IDPs). The carriers are organic carbon and amorphous silicates that are abundant in IDPs and in the interstellar medium. These multiple carriers may explain the enigmatic invariant central wavelength and variable bandwidth of the astronomical 2175 angstrom feature.
Lost in Translation?
Authors: McCook Stuart
Published: January 2005

Plants and Empire
Colonial Bioprospecting in the Atlantic World.
By Londa Schiebinger
. Harvard University Press, Cambridge, MA, 2004. 318 pp. $39.95, £25.95, €36.90. ISBN 0-674-01487-1.

The author examines the factors that influenced how and to what extent knowledge of plants used by indigenous and African inhabitants of the Caribbean moved into--and failed to move into--Europe and colonial plantations around the world.
Herpes Simplex Virus 1 Infection Activates the Endoplasmic Reticulum Resident Kinase PERK and Mediates eIF-2α Dephosphorylation by the γ
1
34.5 Protein
Authors: Cheng Guofeng , Feng Zongdi , He Bin
Published: January 2005

The γ
1
34.5 protein of herpes simplex virus (HSV) plays a crucial role in virus infection. Although the double-stranded RNA-dependent protein kinase (PKR) is activated during HSV infection, the γ
1
34.5 protein inhibits the activity of PKR by mediating dephosphorylation of the translation initiation factor eIF-2α. Here we show that HSV infection also induces phosphorylation of an endoplasmic reticulum (ER) resident kinase PERK, a hallmark of ER stress response. The virus-induced phosphorylation of PERK is blocked by cycloheximide but not by phosphonoacetic acid, suggesting that the accumulation of viral proteins in the ER is essential. Notably, the maximal phosphorylation of PERK is delayed in PKR
+/+
cells compared to that seen in PKR
−/−
cells. Further analysis indicates that hyperphosphorylation of eIF-2α caused by HSV is greater in PKR
+/+
cells than in PKR
−/−
cells. However, expression of the γ
1
34.5 protein suppresses the ER stress response caused by virus, dithiothreitol, and thapsigargin as measured by global protein synthesis. Interestingly, the expression of GADD34 stimulated by HSV infection parallels the status of eIF-2α phosphorylation. Together, these observations suggest that regulation of eIF-2α phosphorylation by the γ
1
34.5 protein is an efficient way to antagonize the inhibitory activity of PKR as well as PERK during productive infection.
An Sp1 Response Element in the Kaposi's Sarcoma-Associated Herpesvirus Open Reading Frame 50 Promoter Mediates Lytic Cycle Induction by Butyrate
Authors: Ye Jianjiang , Shedd Duane , Miller George
Published: January 2005

Kaposi's sarcoma-associated herpesvirus (KSHV) can be driven into the lytic cycle in vitro by phorbol esters and sodium butyrate. This report begins to analyze the process by which butyrate activates the promoter of KSHV open reading frame 50 (ORF50), the key viral regulator of the KSHV latency to lytic cycle switch. A short fragment of the promoter, 134 nucleotides upstream of the translational start of ORF50, retained basal uninduced activity and conferred maximal responsiveness to sodium butyrate. The butyrate response element was mapped to a consensus Sp1-binding site. By means of electrophoretic mobility shift assays, both Sp1 and Sp3 were shown to form complexes in vitro with the ORF50 promoter at the Sp1 site. Butyrate induced the formation of a group of novel complexes, including several Sp3-containing complexes, one Sp1-containing complex, and several other complexes that were not identified with antibodies to Sp1 or Sp3. Formation of all butyrate-induced DNA-protein complexes was mediated by the consensus Sp1 site. In insect and mammalian cell lines, Sp1 significantly activated the ORF50 promoter linked to luciferase. Chromatin immunoprecipitation experiments in a PEL cell line showed that butyrate induced Sp1, CBP, and p300 binding to the ORF50 promoter in vivo in an on-off manner. The results suggest that induction of the KSHV lytic cycle by butyrate is mediated through interactions at the Sp1/Sp3 site located 103 to 112 nucleotides upstream of the translational initiation of ORF50 presumably by enhancing the binding of Sp1 to this site.
Reverse Genetics System for Porcine Enteric Calicivirus, a Prototype Sapovirus in the
Caliciviridae
Authors: Chang Kyeong-Ok , Sosnovtsev Stanislav S. , Belliot Gaël , Wang Qiuhong , Saif Linda J. , Green Kim Y.
Published: January 2005

A porcine enteric calicivirus (PEC), strain Cowden in the genus
Sapovirus
of the
Caliciviridae
family, can be propagated in a porcine kidney continuous cell line (LLC-PK) in the presence of bile acids in the cell culture medium. A full-length cDNA copy of the Cowden PEC genome was cloned into a plasmid vector directly downstream from the T7 RNA polymerase promoter, and capped RNA transcripts derived from this clone were infectious when transfected into LLC-PK cells. The recovery of PEC after transfection of RNA transcripts was dependent on the presence of bile acids, consistent with our recent identification of a bile acid-mediated signaling pathway required for PEC replication (Chang et al., Proc. Natl. Acad. Sci. USA
101:
8733-8788, 2004). Recovery of virus was verified by detection of PEC antigen in transfected cells by immunofluorescence and enzyme-linked immunosorbent assays, direct observation of recovered viral particles by electron microscopy, and partial sequence analysis of their genomes (first 1,070 nucleotides) to differentiate them from tissue culture-adapted parental virus. The recovered virus retained its ability to infect piglets when administered by the oral route and showed an attenuated phenotype similar to that of the tissue culture-adapted parental virus. This reverse genetics system for PEC provides a new tool to study the molecular basis of replication and pathogenesis for caliciviruses associated with diarrheal disease.
The Phosphorylation Status of the Serine-Rich Region of the Human Cytomegalovirus 86-Kilodalton Major Immediate-Early Protein IE2/IEP86 Affects Temporal Viral Gene Expression
Authors: Barrasa M. Inmaculada , Harel Noam Y. , Alwine James C.
Published: January 2005

The 86-kDa major immediate-early protein (IE2/IEP86) of human cytomegalovirus (HCMV) contains a serine-rich region (amino acids 258 to 275) with several consensus casein kinase II (CKII) sites. We performed extensive mutational analysis of this region, changing serines to alternating alanines and glycines. Mutation of the serines between amino acids 266 and 275 eliminated in vitro phosphorylation by CKII. In vitro CKII phosphorylation of the serines between amino acids 266 and 269 or between amino acids 271 and 275 inhibited the ability of IE2/IEP86 to bind to TATA-binding protein. Correspondingly, nonphosphorylatable mutants in these regions showed increased activation of specific HCMV gene promoters in transfection studies. Viruses containing mutations of the serines throughout the entire region (amino acids 258 to 275) or the second half (amino acids 266 to 275) of the region showed delayed expression of all viral proteins tested and, correspondingly, delayed growth compared to wild-type HCMV. Mutation of the serines in the first half of the serine-rich region (amino acids 258 to 264) or between amino acids 266 and 269 propagated very slowly and has not been further studied. In contrast, mutation of the serines between amino acids 271 and 275 resulted in accelerated virus growth and accelerated temporal expression of viral proteins. These results suggest that the serine-rich region is structurally complex, possibly affecting multiple functions of IE2/IEP86. The data show that the phosphorylation state of the serine-rich region, particularly between amino acids 271 and 275, modulates the temporal expression of viral genes.
Mutual Interference between Genomic RNA Replication and Subgenomic mRNA Transcription in Brome Mosaic Virus
Authors: Grdzelishvili Valery Z. , Garcia-Ruiz Hernan , Watanabe Tokiko , Ahlquist Paul
Published: January 2005

Replication by many positive-strand RNA viruses includes genomic RNA amplification and subgenomic mRNA (sgRNA) transcription. For brome mosaic virus (BMV), both processes occur in virus-induced, membrane-associated compartments, require BMV replication factors 1a and 2a, and use negative-strand RNA3 as a template for genomic RNA3 and sgRNA syntheses. To begin elucidating their relations, we examined the interaction of RNA3 replication and sgRNA transcription in
Saccharomyces cerevisiae
expressing 1a and 2a, which support the full RNA3 replication cycle. Blocking sgRNA transcription stimulated RNA3 replication by up to 350%, implying that sgRNA transcription inhibits RNA3 replication. Such inhibition was independent of the sgRNA-encoded coat protein and operated in
cis
. We further found that sgRNA transcription inhibited RNA3 replication at a step or steps after negative-strand RNA3 synthesis, implying competition with positive-strand RNA3 synthesis for negative-strand RNA3 templates, viral replication factors, or common host components. Consistent with this, sgRNA transcription was stimulated by up to 400% when mutations inhibiting positive-strand RNA3 synthesis were introduced into the RNA3 5′-untranslated region. Thus, BMV subgenomic and genomic RNA syntheses mutually interfered with each other, apparently by competition for one or more common factors. In plant protoplasts replicating all three BMV genomic RNAs, mutations blocking sgRNA transcription often had lesser effects on RNA3 accumulation, possibly because RNA3 also competed with RNA1 and RNA2 replication templates and because any increase in RNA3 replication at the expense of RNA1 and RNA2 would be self-limited by decreased 1a and 2a expression from RNA1 and RNA2.