bluuebunny/crossref_metadata_2025 huggingface dataset:
A Distinct Asymmetrical Pattern of Cortical Malformation: Large Unilateral Malformation of Cortical Development with Contralateral Periventricular Nodular Heterotopia in Three Pediatric Cases
Authors: Poduri Annapurna , Golja Anna , Riviello James J. , Bourgeois Blaise F. D. , Duffy Frank H. , Takeoka Masanori
Published: August 2005

Summary:  Purpose: To describe a distinct asymmetrical pattern of cortical malformation with large focal malformations of cortical development (MCDs) and contralateral periventricular nodular heterotopia (PNH).

Methods: We identified three patients with epilepsy and focal EEG abnormalities. Each patient underwent 1.5‐Tesla magnetic resonance imaging (MRI) to obtain sagittal T1‐weighted, axial fluid‐attenuated inversion recovery (FLAIR), fast spin‐echo (FSE) T2‐weighted, and coronal fast spin‐echo inversion recovery (FSEIR) T2‐weighted images; coronal spoiled gradient recalled (SPGR) T1‐weighted images were obtained in two cases.

Results: Patient 1, an 18‐year‐old right‐handed man, had a 4‐year history of intractable seizures. MRI revealed a right frontal subcortical heterotopia (SH) and a single left anterior PNH.

Patient 2, a 10‐year‐old left‐handed boy, had a 4‐year history of epilepsy. MRI revealed a large region of SH in the left temporal, parietal, and occipital lobes and three right‐sided PNH.

Patient 3, a 16‐month‐old girl, had medically refractory infantile spasms. MRI revealed a large MCD in the left parietal lobe with contiguous underlying periventricular heterotopia as well as a small contralateral PNH.

Conclusions: These cases together illustrate a distinct asymmetrical pattern of a large focal MCD with small contralateral PNH. The asymmetrical involvement of the two hemispheres suggests that the stage of maximal disruption of cortical development may differ between the two hemispheres. Further study into the mechanisms underlying such asymmetrical patterns of cortical malformation should enhance our understanding of cortical development as well as hemispheric lateralization.
Nonconvulsive Status Epilepticus after Temporal Lobectomy
Authors: Burneo Jorge G. , Steven David , McLachlan Richard S.
Published: August 2005

Summary:  Acute brain injury can cause nonconvulsive status epilepticus (NCSE). However, this condition has not been reported immediately after brain surgery. We describe a patient who had NCSE in the recovery room after an otherwise successful right temporal lobectomy and emphasize the usefulness of electroencephalography in this situation.
Epileptogenesis due to Peripheral Injury as a Cause of Focal Epilepsy
Authors: Spiller Allison E. , Guberman Alan , Bartolomei Fabrice , Zifkin Benjamin , Andermann Frederick
Published: August 2005

Summary:  Purpose: To report three patients in whom focal epilepsy developed shortly after painful soft tissue injuries to their hands.

Methods: Case reports.

Results: The attacks started in the injured hand. No evidence was found of an underlying brain lesion by history or from imaging studies.

Conclusions: These cases suggest the possibility that the injuries led to a plastic change in the sensory/motor cortex, leading to increased excitability and ultimately to seizures. This suggests that epileptogenesis can occur in response to painful peripheral stimuli in some individuals.
Thiol Redox State and Lipid and Protein Oxidation in the Mouse Striatum after Pentylenetetrazol‐induced Epileptic Seizure
Authors: Patsoukis Nikolaos , Zervoudakis George , Georgiou Christos D. , Angelatou Fevronia , Matsokis Nikolaos A. , Panagopoulos Nikolaos T.
Published: August 2005

Summary: Purpose:In the present study, we examined the effects of pentylenetetrazol (PTZ) administration on the thiol redox state (TRS), lipid peroxidation, and protein oxidation in the mouse striatum to (a) quantitate the major components of TRS and relate them to oxidative stress, and (b) investigate whether neuronal activation without synchronization, induced by subconvulsive doses of PTZ, can cause similar qualitative effects on TRS in this brain area. Specifically, we examined the TRS components glutathione (GSH), glutathione disulfide (GSSG), cysteine (CSH), protein thiols (PSH), and the protein (P) and nonprotein (NP/R) disulfides PSSR, NPSSR, NPSSC, and PSSP.

Methods:TRS components were measured photometrically (GSSG enzymatically) as were lipid peroxidation and protein oxidation.

Results:GSH, GSSG, and NPSSC levels are decreased by 45%, 38% and 26%, respectively, at 15 min after seizure; PSSP and PSSR levels and lipid peroxidation are increased by 47%, 200% and 22%, respectively, whereas CSH, NPSSR, PSH, PSSC, and protein carbonyl levels do not change. At 30 min after seizure, GSH, GSSG, CSH, NPSSC, and protein carbonyl levels are decreased by 26%, 62%, 25%, 40%, and 13%, respectively. PSSP and NPSSR levels are increased by 30% and 42%, respectively, whereas PSH, PSSC, PSSR, and lipid peroxidation remain unchanged. At 24 h after seizure, GSH, NPSSR, PSSR, and lipid‐peroxidation levels return to normal; GSSG, CSH, NPSSC, and protein carbonyl levels are decreased by 44%, 22%, 30%, and 27%, respectively.

Conclusions:The significant decrease in GSH, GSSG, CSH, and NPSSC and the increase in PSSP, NPSSR, PSSR, and lipid peroxidation after PTZ‐induced seizure strongly suggest increased oxidative stress in the mouse striatum.
Characteristics of Headache Associated with Intractable Partial Epilepsy
Authors: Yankovsky Alexei E. , Andermann Frederick , Bernasconi Andrea
Published: August 2005

Summary:  Purpose: The association between headache (HA) and epilepsy is well known. However, few previous studies characterized HA types and head sensations (HSens) in large populations of individuals with well‐defined forms of epilepsy.

Methods: To analyze the incidence of HA in such a group, we compare HA and non‐HA patients to identify special predictive factors for HAs or migraine. We also investigate the pathologically verified group for possible correlations with HAs or migraine. One hundred consecutive patients undergoing presurgical evaluation for pharmacologically intractable partial epilepsy were interviewed. For each HA type, we inquired about lateralization, localization, quality of HA, and results of treatment.

Results: Periictal HAs were reported by 47 patients. Of those, 11 had preictal HA (PIHA), and 44 had postictal HA (PostHA). Eight patients had both PIHA and PostHA. Interictal HAs (InterHAs) were reported by 31 patients. Twenty‐nine (62%) of 47 patients had frontotemporal HAs. Twenty‐five patients had migraine‐like HA without aura: 18 (60%) of 30 patients with temporal lobe epilepsy (TLE) and seven (41%) of 17 with extratemporal epilepsy (ETE). No correlation between pathology and presence of HA was found in 59 pathologically verified patients, except in four who had arteriovenous malformations (AVMs): three had and one did not have HAs. Eighteen patients had, in addition, poorly localized and ill‐described HSens other than HAs.

Conclusions: We confirm an association between focal epilepsy and HAs, including migraine without aura. This is true for both TLE and ETE. PIHA and even prodromal HA may be related to the epileptic discharge and may have lateralizing value. This association is not recognized by the current International Headache Society (IHS) classification. The presence of HA and migraine is not related to the underlying epileptogenic pathology except in patients with AVMs.
Hyperorality in Epileptic Seizures: Periictal Incomplete Klüver–Bucy Syndrome
Authors: Janszky Jozsef , Fogarasi Andras , Magalova Vafa , Tuxhorn Ingrid , Ebner Alois
Published: August 2005

Summary:  Purpose: To analyze systematically hyperorality associated with epileptic seizures and its relation to the localization of epileptic activity.

Methods: To identify patients with periictal hyperorality, we reviewed video‐recordings of 269 patients (aged 6–59 years) who had consecutively undergone presurgical evaluations including ictal video‐EEG recordings and high‐resolution magnetic resonance imaging (MRI) and had had epilepsy surgery because of intractable frontal (FLE) or temporal lobe epilepsy (TLE). Periictal hyperorality was defined if patients put or unambiguously intended to put nonfood items into their mouths during or after at least one of the reviewed seizures. For the further analysis, we included only patients with periictal hyperorality. We reviewed their medical records and reexamined their ictal video‐EEG recordings.

Results: We identified eight patients (six women) aged 8–59 years who had hyperorality during or after seizures. Seven patients had TLE, and one patient had frontal lobe epilepsy (FLE). Three of these patients underwent right‐sided surgery, whereas five patients had surgery on the left. Three patients exhibited ictal and five showed postictal hyperorality. Interictal EEG suggested bilateral interictal epileptiform discharges (IEDs) in three patients; in two other patients, no IEDs were detected. Ictal EEG suggested bilateral involvement in six cases. Patients with unilateral epileptiform activity had left TLE.

Conclusions: Periictal hyperorality is a rare phenomenon occurring in 3% of the investigated epilepsy population. We suggest that periictal hyperorality is an ictal–postictal mental disturbance, an incomplete Klüver–Bucy syndrome. In most patients, bilateral seizure activity plays an important role in the pathomechanism, but it would appear that left‐sided epileptic activity without contralateral involvement also can cause periictal hyperorality.
Analysis of Atrial and Ventricular Performance by Tissue Doppler Imaging in Patients with Atrial Septal Defects before and after Surgical and Catheter Closure
Authors: Abd El Rahman M. Y , Hui W. , Timme J. , Ewert P. , Berger F. , Dsebissowa F. , Hetzer R. , Lange P. E. , Abdul‐Khaliq H.
Published: August 2005

Objective: To compare the effects of surgical and device closure of atrial septal defects on atrial and ventricular performance assessed by the novel tissue Doppler derived strain rate. Background: Despite the increasing number of transcatheter closures, there is no information comparing the effect of the transcatheter closure technique on atrial performance with that of conventional surgery. Tissue Doppler derived strain rate can effectively quantify local myocardial function independent of the overall heart motion. Design and patients: Twenty‐four patients [aged 21.5 (6–70) years] with isolated atrial septal defect of the secondum type before and 1 week after surgical (n = 12) or Amplatzer Septal Occluder closure (n = 12) and 30 healthy controls [aged 26.0 (2–58) years] were studied. Atrial and ventricular strain rate curves were assessed in the middle of their corresponding lateral walls in an apical four‐chamber view. The systolic, early diastolic, and late diastolic strain rates peaks were measured. Results: Compared to preclosure condition, the right atrial late diastolic (P < 0.01), right ventricular systolic (P < 0.01), right ventricular early diastolic (P < 0.01), and left atrial late diastolic peak (P < 0.01) strain rates were reduced after surgery but not after Amplatzer Septal Occluder closure. The LV parameters did not significantly differ before and after atrial septal defect closure by either technique. Conclusions: In contrast to surgery, transcatheter closure of atrial septal defect preserves atrial and right ventricular function. Tissue Doppler derived strain rate can be applied to provide quantitative analysis of regional atrial and ventricular performance.
An Echocardiographic Analysis of the Long‐Term Effects of Carvedilol on Left Ventricular Remodeling, Systolic Performance, and Ventricular Filling Patterns in Dilated Cardiomyopathy
Authors: Rahko Peter S.
Published: August 2005

Background: The long‐term clinical benefit of beta blockade is well recognized, but data quantifying long‐term effects of beta blockade on remodeling of the left ventricle (LV) is limited. Methods: This consecutive series evaluates the long‐term response of the LV to the addition of carvedilol to conventional therapy for dilated cardiomyopathy. There were 33 patients who had a LV ejection fraction <45%, LV enlargement and symptomatic heart failure. Quantitative Doppler echocardiography was performed at baseline 6, 12, 24, and 36 months after initiation of carvedilol to evaluate LV ejection fraction, LV volume, wall stress, mass, regional function, and diastolic performance. Results: Compared to baseline there was a significant and sustained reduction in end‐systolic volume and end‐systolic wall stress with a corresponding improvement in LV ejection fraction. The LV mass did not decline but relative wall thickness increased toward normal. An analysis of regional wall motion responses showed an improvement in all areas, particularly the apical, septal, and lateral walls that was significantly more frequent in patients with a nonischemic etiology. Filling patterns of the LV remained abnormal throughout the study but changed with therapy suggesting a decline in filling pressures. These changes were sustained for 3 years. Conclusion: (1) The addition of carvedilol to conventional therapy for a dilated cardiomyopathy significantly improves LV ejection fraction and reduces LV end‐systolic volume and wall stress for at least 3 years, (2) the response to 6 months of treatment predicts the long‐term response, (3) the typical response is partial improvement of the LV, complete return to normal size, and function is uncommon, and (4) abnormalities of LV filling persist in virtually all patients throughout the course of treatment.
Comparison of Acoustic Densitometry and Dobutamine Echocardiography for an Assessment of Myocardial Viability
Authors: Panovský Roman , Meluzín Jaroslav , Kincl Vladimír , Štětka František , Fischerová Blanka , Vespalec Jaroslav
Published: August 2005

Aim: The aim of this study has been to compare acoustic densitometry and dobutamine echocardiography for an assessment of myocardial viability. Methods and results: Thirty‐four patients with coronary artery disease and dysfunctional myocardial segments, who were referred for myocardial revascularization, underwent a viability assessment using low‐dose dobutamine echocardiography and acoustic densitometry. Results of the two techniques were compared to follow‐up resting echocardiography. This follow‐up examination was performed at a mean of 3 months after successful revascularization in order to assess the recovery of function in revascularized, initially dysfunctional segments. Echocardiography was performed in standard views using 16‐segment model of the left ventricle. Viable myocardium was identified by the augmentation of systolic thickening of an abnormal segment by at least one grade during dobutamine infusion and by the value of the maximal amplitude of cyclic variation of integrated backscatter. Acoustic densitometry had the sensitivity and specificity to predict functional recovery 90% and 77%, respectively. Dobutamine echocardiography had the sensitivity and specificity to predict contractile reserve 83% and 81%, respectively. The results were statistically comparable. Concordance between these methods was 80%. Conclusion: Acoustic densitometry and dobutamine echocardiography did not statistically differ in the prediction of functional recovery dysfunctional myocardial segments after revascularization.
Coronary Reserve in Takayasu's Arteritis: Transesophageal Echocardiographic Analysis
Authors: Espinola‐Zavaleta Nilda , Soto María Elena , Bauk Lucas , Miguel Casanova José , Keirns Candace , Vanzzini Nydia Avila , Reyes Pedro
Published: August 2005

Background: The incidence of coronary arteries lesion in Takayasu's arteritis varies from 9% to 10% and is usually discovered at autopsy. Recent studies have demonstrated the value of echocardiography in noninvasive detection of significant coronary stenosis. Aim: The aim of our study was to evaluate coronary reserve in 15 patients with Takayasu's arteritis using contrast transesophageal echocardiography (Optison). Methods: Transesophageal echocardiogram under basal conditions and in the hyperemic phase with dipyridamole challenge, myocardial perfusion studies and coronary angiography were performed on all patients. Seventy‐three percent of them had histories of systemic hypertension, and the most frequent cardiovascular symptoms were shortness of breath (80%), headache (46%), angina (40%), and dizziness (33%). Results: The transthoracic echocardiogram showed left ventricular systolic dysfunction in 6% and diastolic dysfunction in 53%. Aortic regurgitation was found in 67% of the patients, and 60% had mitral and/or tricuspid regurgitation. Coronary reserve was diminished in 3 patients with significant coronary lesions and in 2 patients with coronary dilation (33%). In the 3 patients with obstructive lesions and diminished coronary reserve, reversible perfusion defects were found with thallium‐201 single‐photon emission computed tomography. One patient with coronary dilation had normal perfusion, while the other demonstrated reversible and irreversible perfusion defects. One patient without coronary lesions and with normal coronary reserve had an irreversible fibrotic changes and the other reversible defects due to abnormal microcirculation. Conclusions: Transesophageal echocardiography is a feasible and promising technique for assessing coronary reserve in patients with Takayasu's arteritis.
Live Three‐Dimensional Transthoracic Echocardiographic Assessment of Ventricular Noncompaction
Authors: Bodiwala Kunal , Miller Andrew P. , Nanda Navin C. , Patel Vinod , Vengala Srinivas , Mehmood Farhat , Upendram Shailendra , Frans Ebenezer
Published: August 2005

We present eight adult patients with noncompaction (four with isolated left ventricular noncompaction and four with combined left and right ventricular noncompaction) in whom live three‐dimensional transthoracic echocardiography (3D TTE) demonstrated multiple, prominent myocardial trabeculations, deep intertrabecular recesses communicating with the ventricular cavity, and a typical honeycombing appearance. In the four patients with combined right and left ventricular noncompaction, very extensive trabeculations in the right ventricle were identified, much more than in normal or hypertrophied right ventricles. Five of the eight patients were not definitively identified to have noncompaction on two‐dimensional (2D) TTE, but the diagnosis was made with 3D TTE. These cases demonstrate the potential usefulness of 3D TTE as a supplement to 2D TTE in the assessment of noncompaction.
Stroke or encephalitis?
Authors: Townend Bradley S , Hanson Julian A , Sturm Jonathan W , Whyte Scott
Published: August 2005

Viral encephalitis is associated with significant morbidity and mortality, particularly when appropriate management is omitted as a result of delayed diagnosis. A case of herpes simplex virus type 1 (HSV‐1) encephalitis is presented, demonstrating that the presentation of confusion, speech difficulties and fever with non‐specific early brain CT appearances can easily be misdiagnosed as pneumonia with stroke. This case highlights the need for increased awareness of HSV‐1 encephalitis among emergency physicians and radiologists, given that the early spectrum of clinical and CT findings can mimic the more common diagnoses of sepsis and stroke.
On the Effect of Dual Weights in Computer Aided Design of Rational Motions
Authors: Purwar Anurag , Ge Qiaode Jeffrey
Published: August 2005

In recent years, it has become well known that rational Bézier and B-spline curves in the space of dual quaternions correspond to rational Bézier and B-spline motions. However, the influence of weights of these dual quaternion curves on the resulting rational motions has been largely unexplored. In this paper, we present a thorough mathematical exposition on the influence of dual-number weights associated with dual quaternions for rational motion design. By deriving the explicit equations for the point trajectories of the resulting motion, we show that the effect of real weights on the resulting motion is similar to that of a rational Bézier curve and how the change in dual part of a dual-number weight affects the translational component of the motion. We also show that a rational Bézier motion can be reparameterized in a manner similar to a rational Bézier curve. Several examples are presented to illustrate the effects of the weights on rational motions.
Scanning capacitance force microscopy imaging of metal-oxide-semiconductor field effect transistors
Authors: Kimura Kenjiro , Kobayashi Kei , Yamada Hirofumi , Matsushige Kazumi , Usuda Koji
Published: August 2005

We investigated two-dimensional carrier profiles in metal-oxide-semiconductor field effect transistors (MOSFETs) using scanning capacitance force microscopy (SCFM), which was based on electrostatic force detection. We successfully obtained clear contrasts on source, drain, and channel regions by contact-mode SCFM, which corresponded to their dopant concentrations. Furthermore, the contrast on the channel region was changed by applying dc offset voltage to the gate electrode. We also compared line profile obtained from the SCFM image with a dopant profile measured by secondary ion mass spectroscopy (SIMS).
Dynamically ordered thin film nanoclusters
Authors: Zhang Wei , Zhang Chi , Kalyanaraman Ramki
Published: August 2005

Experimental evidence for dynamic modification of a growing thin film into ordered nanoclusters is presented. Co nanoclusters of approximately 50nm diameter were assembled into one-dimensionally ordered arrays spaced 400nm apart on Si(100) substrates during film growth. This ordered arrangement was achieved under e-beam evaporation of Co with simultaneous two-beam laser interference irradiation of the substrate. The ordering length scale was consistent with the two-beam fringe spacing of 400nm. In comparison, the unirradiated film shows a random distribution of Co clusters with average diameter of 17nm. The mechanism for assembly is tentatively attributed to thermal effects arising from the spatially periodic laser interference heating of the substrate and∕or film. This one step process, without the need of any pre- or postpatterning of the substrate or film, is promising as an economical and simple approach to assemble ordered nanostructured films.
Interaction of single pentacene molecules with monatomic Cu∕Cu(111) quantum wires
Authors: Lagoute Jérôme , Fölsch Stefan
Published: August 2005

An ultrahigh vacuum low-temperature scanning tunneling microscope operated at 7 K is used to assemble Cu adatom chains on a Cu(111) surface by atom manipulation. Cu atoms within the close-packed chain reside on nearest-neighbor fcc hollow sites (Cu–Cu spacing 2.55 Å) along the ⟨110⟩ in-plane directions. Spectroscopic measurements of the differential tunneling conductance dI∕dV reveal that the monatomic Cu chain exhibits unoccupied one-dimensional (1D) quantum well states trapped in the pseudogap of the ⟨111⟩-projected Cu bulk bands. These chain-localized states are described by a 1D energy band centered 3.2 eV above the Fermi level (total band width 3.6 eV) and derive from spz hybrid atomic orbitals associated with the single Cu∕Cu(111) adatom. Pentacene molecules (C22H14) deposited on Cu(111) by thermal evaporation adopt a planar adsorption geometry with their long molecular axis aligned with the ⟨110⟩ in-plane directions. The organic molecule can be laterally manipulated along different high-symmetry directions of the substrate via attractive tip/molecule interactions. Lateral manipulation is also capable to attach single pentacene molecules to the ends of assembled Cu chains with atomic-level precision. We find (i) an enhanced adsorptive binding of the attached molecule characterized by spatial overlap between its carbon framework and the outermost chain atoms, (ii) persistence of the chain-localized states for the molecule-chain hybrid structure, and (iii) a clear correspondence between the number of Cu chain atoms involved in the spatial overlap and the observed energetic upward shift of the chain-localized quantum levels.
Control on self-organization of InGaAs/GaAs(100) quantum-dot chains
Authors: Wang Zh. M. , Mazur Yu. I. , Holmes K. , Salamo G. J.
Published: August 2005

The spontaneous formation of long chains of quantum dots during the growth of InGaAs/GaAs multiple layers has been reported recently. The effects of In content and spacer on the evolution of dotchains are investigated in the present work. By reducing the In content in the InGaAs layer, the quantum dots in chains are more connected and finally arrays of quantum wires would form. By changing the GaAs spacer layer thickness, the vertical and also lateral spacing between dotchains can be continually tuned. The capability to insert a thick layer of AlGaAs as part of the spacer layer enables us to fabricate InGaAs quantum-dot chains without vertical electronic coupling. The achieved control of self-assembly of organized InGaAs quantum dots may be advantageous for novel optoelectronic applications.
Nitrogen diffusion and accumulation at the Si∕SiO2 interface in SiO2∕Si3N4∕SiO2 structures for nonvolatile semiconductor memories
Authors: Saraf Meirav , Edrei Rachel , Shima-Edelstein Ruth , Roizin Yakov , Hoffman Alon
Published: August 2005

Time-of-flight secondary ion mass spectrometry (SIMS) depth profiling was used to study nitrogen distribution in SiO2∕Si3N4∕SiO2 (ONO) structures employed in advanced semiconductor memories. We have investigated different factors that affect nitrogen accumulation at the Si∕SiO2 interface of the ONO structure. To isolate the impact of ion beam enhanced nitrogen diffusion towards the Si∕SiO2 interface in SIMS measurements, the top silicon oxide and silicon nitride layers were chemically etched before the SIMS procedure. Thermal diffusion effects were investigated by comparing specimens with different thermal budgets and different thickness of layers in the ONO stack. Our results unambiguously suggest that nitrogen can be accumulated at the Si∕SiO2 interface during ONO fabrication.
Effect of AlN nucleation layer growth conditions on buffer leakage in AlGaN∕GaN high electron mobility transistors grown by molecular beam epitaxy (MBE)
Authors: Poblenz C. , Waltereit P. , Rajan S. , Mishra U. K. , Speck J. S. , Chin P. , Smorchkova I. , Heying B.
Published: August 2005

The effect of the AlN nucleation layer growth conditions on buffer leakage in unintentionally doped AlGaN∕GaN high electron mobility transistors was investigated. The samples were grown by rf-plasma assisted molecular beam epitaxy on 4H–SiC (0001). Drain-source leakage currents were found to be markedly different for samples grown with different Al∕N flux ratios during the AlN nucleation layer. Growth of N-rich nucleation layers (Al∕N<1) resulted in a significant reduction in buffer leakage. Secondary ion mass spectroscopy results showed that Si incorporation into Al-rich AlN layers (Al∕N>1) grown on SiC was as high as ∼1–2×1018atoms∕cm3. In contrast, Si incorporation into N-rich AlN layers was two orders of magnitude lower, ∼2×1016atoms∕cm3. Initial devices grown on low-leakage material realized via N-rich nucleation yielded output power densities at 4GHz of 4.8W∕mm with a power added efficiency (PAE) of 62% at a drain bias of 30V, and 8.1W∕mm with a PAE of 38% at a drain bias of 50V.
Effects of surface states and Si-interlayer based surface passivation on GaAs quantum wires grown by selective molecular beam epitaxy
Authors: Shiozaki Nanako , Sato Taketomo , Hasegawa Hideki
Published: August 2005

Effects of surface states and surface passivation on photoluminescence (PL) properties of GaAs quantum wires (QWRs) are investigated. QWR samples were grown on (001) and (111)B substrates by the selective molecular beam epitaxy (MBE) method. For surface passivation, an ultrathin (about 1 nm) Si interface control layer (Si ICL) was grown by MBE as an interlayer. In both of the selectively grown QWRs on (001) and (111)B substrates, the PL intensity reduced exponentially with reduction of their wire-to-surface distance, being coexistent with a more gradual reduction due to carrier supply reduction. The exponential reduction was explained in terms of interaction between surface states and quantum confined states leading to tunneling assisted nonradiative recombination through surface states. Surface passivation by the Si-ICL method almost completely recovered PL intensities not only for QWRs on the (001) substrate, but also for QWRs on the (111)B substrate.
Control of InAs∕GaAs quantum dot density and alignment using modified buffer layers
Authors: Ye W. , Hanson S. , Reason M. , Weng X. , Goldman R. S.
Published: August 2005

We have investigated the patterning effects of GaAs buffers during the growth of InAs∕GaAs quantum dot (QD) superlattices (SLs). One-, five-, and ten-period QD SLs were deposited on GaAs buffer layers grown at 580°C and/or 500°C, with various annealing steps. High-temperature-grown buffers consist of relatively flat surfaces, while low-temperature-grown buffers contain “mound-like” features elongated along the [11¯0] direction. Isotropic distributions of QDs are observed for QD growth on flat buffers. Interestingly, QD alignment along the [11¯0] direction is observed for QD SL growth on buffers containing mounds. This anisotropic QD alignment is enhanced as the number of QD SLs increases and is dependent on the density of mounds. For flat buffers, the density of QDs decreases with stacking, consistent with the model of Tersoff [J. Tersoff, C. Teichert, and M. G. Lagally, Phys. Rev. Lett. 76, 1675 (1996)]. However, for buffers containing mounds, this effect is compensated by an increase in QD density. We propose a mechanism for QD nucleation, based upon buffer layer patterning leading to an undulated In-enriched GaAs spacer layer following the initial layer of QDs.
Solid state amorphization at the room temperature deposited Ni∕Si(100) interface
Authors: Wen J.-F. , Wang L.-B. , Liu C.-H. , Lee H.-H. , Hwang J. , Ouyang C.-P. , Pi T.-W. , Hwang J.-W. , Cheng C.-P.
Published: August 2005

The amorphous Ni–Si layer at the room temperature deposited Ni∕Si(100)-2×1 interface has been characterized by synchrotron ultraviolet photoemission. The growth kinetics of the amorphous Ni–Si layer strongly depends on the interaction between Ni and Si(100)-2×1 at the initial stage of Ni deposition. Three amorphous NixSiy alloys, a-NiSi2, a-Ni2Si, and a-NiSi, are evolved from three different Ni–Si bonding sites on Si(001)-2×1 at 1 ML Ni coverage. The a-NiSi2 bonding environment ceases to grow at 2 ML Ni coverage, which corresponds to the penetration of Ni atoms into the tetrahedral sites around the subsurface of Si(100)-2×1. While a-Ni2Si, and a-NiSi correspond to two different bonding sites above the Si dimers on Si(100)-2×1. A critical coverage of ∼4 ML exists, beyond which a-Ni2Si becomes the dominant phase as predicted by the “first phase rule” at a metal/Si interface. The growth mode of the amorphous Ni–Si layer was proposed to be layer-by-layer-like at Ni coverage less than 6 ML.
Uniformity and control of surface morphology during growth of GaN by molecular beam epitaxy
Authors: Poblenz C. , Waltereit P. , Speck J. S.
Published: August 2005

A “modulated growth” technique has been introduced to achieve large area uniformity and surface morphology control during rf plasma assisted molecular beam epitaxy of GaN. The technique consists of modulating the surface coverage of Ga through short-period shuttering of Ga, N, or Ga and N together (e.g., 50–100Å growth periods), to achieve alternating high and low surface coverages of Ga on the (0001) GaN surface. The periods of growth with high Ga flux provide saturation coverage of Ga (∼2.5 ML Ga plus Ga droplets) over the full wafer, while the subsequent growth with low Ga flux facilitates a time-averaged Ga flux which is just below the crossover for droplet formation at the growth temperature. The growth transients in the Ga droplet regime are necessary to maintain smooth, pit-free surface morphologies, and the subsequent growth with low Ga flux suppresses droplet buildup over time. The process is monitored in situ utilizing reflection high energy electron diffraction and line-of-sight quadrupole mass spectroscopy. Results are presented which demonstrate that this approach is an effective means to achieve uniform surfaces over both 1∕4 and 2in. wafer sizes during nonbonded growth. The effects of temperature nonuniformities were mitigated and a surface free of both pitting and droplets has been realized over large areas.
Optimization of an inductively coupled plasma etching process of GaInP∕GaAs based material for photonic band gap applications
Authors: Combrié S. , Bansropun S. , Lecomte M. , Parillaud O. , Cassette S. , Benisty H. , Nagle J.
Published: August 2005

In this article, we investigate the dry etching of GaInP∕GaAs based material system using an inductively coupled plasma (ICP) etching system. In a view to develop a suitable ICP process for the etching of aluminum-free material, ridge waveguides have been fabricated and the effects of the ICP parameters have been assessed. The coil power and the platen power have been varied at constant pressure and temperature for a chlorine-based process. The surface quality, sidewall profile, and selectivity have been reported. We also demonstrate the optimization of the chlorine-based process for deep etching and its subsequent implementation in photonic band gap device fabrication for 1.55μm optical applications. The optimized process has been shown to provide a high aspect ratio and a good selectivity for 250nm diam holes with a depth of 3μm in the GaInP∕GaAs material system. The influence of the ICP parameters on this material system have been analyzed mainly by scanning electron microscopy with particular attention drawn to the ways of reducing trenching, an effect commonly associated with ICP etching.
Multi-axis retarder arrays by masked oblique deposition
Authors: Arnold M. D. , Hodgkinson I. J. , Wu Q. H. , Blaikie R. J.
Published: August 2005

We report a technique for single-deposition production of arrays with differently oriented nano-structured elements, which we optimize for application to form-birefringent retarder arrays. The technique involves masking of oblique physical vapor deposition, manipulating the local availability of vapor angles to create spatially variant properties in the structured coating. We have designed a variety of retarder arrays using symmetry considerations, and constructed a selection based on suitability for spatially multiplexed complete-Stokes polarimetry. In particular, we emphasize square lattice designs with a two-by-two repeat unit, consisting of three retarders with azimuths at 0°, 45° and 90° and a zero-retardation element. The silicon retarder arrays were tested using visible-wavelength transmission techniques which confirm the success of the method. Finally, we discuss some considerations for application of the technique to microlithography, and we infer a lateral resolution limit related to the coating thickness.
Deep etching of silicon with smooth sidewalls by an improved gas-chopping process using a Faraday cage and a high bias voltage
Authors: Min Jae-Ho , Lee Jin-Kwan , Moon Sang Heup , Kim Chang-Koo
Published: August 2005

A silicon substrate, masked with oxide lines with a spacing of 1μm, was etched using a gas-chopping process designed to enhance mask selectivity and produce a highly anisotropic etch profile with ripple-free sidewalls. The gas-chopping process employed a high bias voltage of −200V and a Faraday cage in the etching step. The use of a high bias voltage relieved the curvature of sidewall ripples that are generated during etch cycles due to the bombardment of energetic ions on the convex portions of the ripples, thus flattening the sidewall surface. The use of a Faraday cage served to suppress the erosion of the mask, thus leading to a high mask selectivity. This can be attributed to an increase in the intrinsic etch selectivity of the Si substrate to the mask due to an increase in the ratio of neutral to ion fluxes on the substrate, and by the suppression of mask faceting due to a reduction in the etch yields of the oxide mask and a CFx film formed on the surface of the mask.
A covenant with the status quo? Male circumcision and the new BMA guidance to doctors
Authors: Fox M , Thomson M
Published: August 2005

This article offers a critique of the recently revised BMA guidance on routine neonatal male circumcision and seeks to challenge the assumptions underpinning the guidance which construe this procedure as a matter of parental choice. Our aim is to problematise continued professional willingness to tolerate the non-therapeutic, non-consensual excision of healthy tissue, arguing that in this context both professional guidance and law are uncharacteristically tolerant of risks inflicted on young children, given the absence of clear medical benefits. By interrogating historical medical explanations for this practice, which continue to surface in contemporary justifications of non-consensual male circumcision, we demonstrate how circumcision has long existed as a procedure in need of a justification. We conclude that it is ethically inappropriate to subject children—male or female—to the acknowledged risks of circumcision and contend that there is no compelling legal authority for the common view that male circumcision is lawful.
Generating node coordinates for shortest-path computations in transportation networks
Authors: Brandes Ulrik , Schulz Frank , Wagner Dorothea , Willhalm Thomas
Published: August 2005

Speed-up techniques that exploit given node coordinates have proven useful for shortest-path computations in transportation networks and geographic information systems. To facilitate the use of such techniques when coordinates are missing from some, or even all, of the nodes in a network we generate artificial coordinates using methods from graph drawing. Experiments on a large set of German train timetables indicate that the speed-up achieved with coordinates from our drawings is close to that achieved with the true coordinates---and in some special cases even better.
Average-optimal single and multiple approximate string matching
Authors: Fredriksson Kimmo , Navarro Gonzalo
Published: August 2005

We present a new algorithm for multiple approximate string matching. It is based on reading backwards enough l-grams from text windows so as to prove that no occurrence can contain the part of the window read, and then shifting the window.We show analytically that our algorithm is optimal on average. Hence our first contribution is to fill an important gap in the area, since no average-optimal algorithm existed for multiple approximate string matching.We consider several variants and practical improvements to our algorithm, and show experimentally that they are resistant to the number of patterns and the fastest for low difference ratios, displacing the long-standing best algorithms. Hence our second contribution is to give a practical algorithm for this problem, by far better than any existing alternative in many cases of interest. On real-life texts, our algorithm is especially interesting for computational biology applications.In particular, we show that our algorithm can be successfully used to search for one pattern, where many more competing algorithms exist. Our algorithm is also average-optimal in this case, being the second after that of Chang and Marr. However, our algorithm permits higher difference ratios than Chang and Marr, and this is our third contribution.In practice, our algorithm is competitive in this scenario too, being the fastest for low difference ratios and moderate alphabet sizes. This is our fourth contribution, which also answers affirmatively the question of whether a practical average-optimal approximate string-matching algorithm existed.
Editorial board
Authors: Lee Newton
Published: August 2005

Our editorial board consists of more than one hundred industry leaders, academic scholars, research scientists, Academy Award winners, Emmy and Grammy recipients from more than sixty organizations including ABC, American Film Insititute, Apple Computer, Ascent Media, AT&T Labs, Avid Technology, Carnegie Mellon, Cox Communications, DreamWorks SKG, Electronic Arts, Fox, Hewlett-Pakcard, IBM, Industrial Light + Magic, Intel, Keio University, Lucent Technologies, Macromedia, Microsoft, MIT, Mitsubishi, Motorola, NBC, Nickelodeon, NVIDIA, Oracle, Panasonic, Real Networks, Sesame Workshop, Sony, Sun Microsystems, THX, UCLA, UCSB, Universial Studios, USC, Viewpoints Research Institute, Vivendi Universal, The Walt Disney Company, Warner Brothers, Yale University, and many other world-renowned universitites and research centers around the world. The editor-in-chief is Newton Lee of Disny Online.
Multimedia tools and applications (MTAP) an international journal
Authors: Roccetti Marco
Published: August 2005

The demand for networked consumer systems and devices is large and growing rapidly. At home, in a car or truck, at work or at play, Internet users want transparent internetworking of their systems and devices to provide them entertainment, information, and communications. This internetworking should be on-demand and should be set up with whomever or whatever users want, regardless of time or location. As a result, consumer networking is gaining increasing attention from industry, spawning a range of dramatically different solutions in different environments such as wireless, wireline, and power-line communications systems. These environments have their own strengths and challenges to overcome. The scope of consumer networking spans from the body area and personal area networks to home and wide area networks. In the not too distant future, we will see Ad hoc networks augmented with sensors sharing network information that enables devices and systems to seamlessly interact with Internet and wide area wireless systems such as WiFi, 3G and future 4G networks. This phenomenon, "Consumer Communications and Networking", has been attracting many researchers in diverse areas from networking to consumer electronics. The focus of this Special Issue is to present the latest approaches and technical solutions in the area of consumer and home networking.
Interviews with Karlheinz Brandenburg
Authors: Brandenburg Karlheinz
Published: August 2005

Interviews with Cynthia Breazeal and Karlheinz Brandenburg—September 10, 2003 and July 22, 2004

Prof. Dr. Cynthia Breazeal, Director of the Robotic Life Group at the MIT Media Lab, and Prof. Dr. Karlheinz Brandenburg, inventor of MP3, have graciously appeared on camera for interviews and joined the ACM Computers in Entertainment magazine's editorial board. Cynthia and Karlheinz are two of the nicest people to talk to and work with. Cynthia talks about her sociable robot Kismet, her role in Steven Spielberg's movie "Artificial Intelligence: AI," and the future of robotics. Karlheinz shares with us the history of MP3, the new spatial audio technology called Wave Field Synthesis, and other fascinating research at the Fraunhofer Institute. The video clips of the interviews are available at http://www.acm.org/pubs/cie.html

Dr. Cynthia Breazeal directs the Robotic Life Group at the MIT Media Lab. She is internationally known for seamlessly blending scientific theories, artistic insights, and engineering principles to create compelling robotic creatures that have a lively and compelling social presence to those who interact with them. Her current research extends these themes in the area of human-robot relations to create cooperative and capable robots that can work and learn in partnership with people. Her research program strives to revolutionize the art and science of human-robot interaction and cooperation - to develop robots that engage us as helpful partners that will ultimately play an valuable, rewarding, and unprecedented role in the everyday lives or ordinary people. More information can be found at http://web.media.mit.edu/~cynthiab/

Dr. Karlheinz Brandenburg manages The Fraunhofer Institute for Digital Media Technology founded in January 2004. He is well known for his work on digital audio coding and perceptual measurement techniques. He received the German Future Award for the development and commercialization of the MP3 music format at the Erlangen based Fraunhofer Institute for Integrated Circuits together with his colleagues Harald Popp and Bernhard Grill in 2000. He is also a full professor and the director of the Institute for Media Technology at Ilmenau Technical University. His current research includes the IOSONO Wave Field Synthesis, audio metadata technologies, and audio applications for specific technological demands. More information can be found at http://www.idmt.fraunhofer.de/presse/textarchiv/vita_brandenburg.pdf
Robot's play
Authors: Brooks Andrew G. , Gray Jesse , Hoffman Guy , Lockerd Andrea , Lee Hans , Breazeal Cynthia
Published: August 2005

Personal robots for human entertainment form a new class of computer-based entertainment that is beginning to become commercially and computationally practical. We expect that the principal manifestation of the robots' entertainment capabilities will be socially interactive game playing. We describe this form of gaming and summarize our current efforts in this direction on our lifelike, expressive, autonomous humanoid robot. Our focus is on teaching the robot via playful interaction using natural social gesture and language. We detail this in terms of two broad categories: teaching as play and teaching with play.
Contextual information access and storytelling in mixed reality using hypermedia
Authors: Romero Luis , SANTIAGO JORGE , CORREIA NUNO
Published: August 2005

This article describes gaming and storytelling activities in a mixed environment that integrates the real and virtual worlds, uses an augmented reality paradigm, and is supported by a structuring and presentation framework for use in context-aware mixed-reality applications. The basis of the framework is a generic hypermedia model that can handle different media elements, objects, and relations between spaces and locations in physical and virtual worlds. A main component of the model deals with providing contextual content according to the state of the application and the person using it. A storytelling layer was also defined, mainly by using the contextual mechanisms of the base model. This layer provides abstractions to storytelling applications that reflect the morphology of common story structures and supports gaming flow. The framework is being tested in a gaming and storytelling environment that integrates the real world, media elements, and virtual 3D worlds.
Adaptation of moveable pop-up technique in 3D animation
Authors: Phing Belinda Teoh Soo , Izani Mohamad , Razak Aishah Abdul
Published: August 2005

To convey a story or message, contemporary 3D animation utilizes a conventional continuity approach in which events are arranged in a smooth, sequential, and uninterrupted manner. The results of good continuity are coherence in visual perception and a seamless flow of action and events from one shot or sequence to another in all motion media. In making a film, continuity coupled with good editing principles and appropriate use of transitions in the post-production phase make for an organized shooting plan. In this article we discuss the potential of adapting a movable pop-up technique as a continuity element for the entire flow in 3D animation. This is done by integrating the technique within the animated story, transforming scenes, and narrating the story from one shot to another continuously by substituting basic editing transitions in a film. These findings demonstrate that movable pop-up animation affects animation timing and is incapable of achieving classical continuity (defined as making transitions as transparent as possible to the audience). Nevertheless, this technique is sufficient to create coherence in visual perception and establish a continuous flow of events within a distinct animation style.