Geometry-Assisted Topological Transitions in Spin Interferometry.

We identify a series of topological transitions occurring in electronic spin transport when manipulating spin-guiding fields controlled by the geometric shape of mesoscopic interferometers. They manifest as distinct inversions of the interference pattern in quantum conductance experiments. We establish that Rashba square loops develop weak-(anti)localization transitions (absent in other geometries as Rashba ring loops) as an in-plane Zeeman field is applied. These transitions, boosted by nonadiabatic spin scattering, prove to have a topological interpretation in terms of winding numbers characterizing the structure of spin modes in the Bloch sphere.

Drift transport of helical spin coherence with tailored spin-orbit interactions.

Most future information processing techniques using electron spins in non-magnetic semiconductors will require both the manipulation and transfer of spins without their coherence being lost. The spin-orbit effective magnetic field induced by drifting electrons enables us to rotate the electron spins in the absence of an external magnetic field. However, the fluctuations in the effective magnetic field originating from the random scattering of electrons also cause undesirable spin decoherence, which limits the length scale of the spin transport. Here we demonstrate the drift transport of electron spins adjusted to a robust spin structure, namely a persistent spin helix. We find that the persistent spin helix enhances the spatial coherence of drifting spins, resulting in maximized spin decay length near the persistent spin helix condition. Within the enhanced distance of the spin transport, the transport path of electron spins can be modulated by employing time-varying in-plane voltages.

New perspectives for Rashba spin-orbit coupling.

In 1984, Bychkov and Rashba introduced a simple form of spin-orbit coupling to explain the peculiarities of electron spin resonance in two-dimensional semiconductors. Over the past 30 years, Rashba spin-orbit coupling has inspired a vast number of predictions, discoveries and innovative concepts far beyond semiconductors. The past decade has been particularly creative, with the realizations of manipulating spin orientation by moving electrons in space, controlling electron trajectories using spin as a steering wheel, and the discovery of new topological classes of materials. This progress has reinvigorated the interest of physicists and materials scientists in the development of inversion asymmetric structures, ranging from layered graphene-like materials to cold atoms. This Review discusses relevant recent and ongoing realizations of Rashba physics in condensed matter.

Direct determination of spin-orbit interaction coefficients and realization of the persistent spin helix symmetry.

The spin-orbit interaction plays a crucial role in diverse fields of condensed matter, including the investigation of Majorana fermions, topological insulators, quantum information and spintronics. In III-V zinc-blende semiconductor heterostructures, two types of spin-orbit interaction--Rashba and Dresselhaus--act on the electron spin as effective magnetic fields with different directions. They are characterized by coefficients α and ß, respectively. When α is equal to ß, the so-called persistent spin helix symmetry is realized. In this condition, invariance with respect to spin rotations is achieved even in the presence of the spin-orbit interaction, implying strongly enhanced spin lifetimes for spatially periodic spin modes. Existing methods to evaluate α/ß require fitting analyses that often include ambiguity in the parameters used. Here, we experimentally demonstrate a simple and fitting parameter-free technique to determine α/ß and to deduce the absolute values of α and ß. The method is based on the detection of the effective magnetic field direction and the strength induced by the two spin-orbit interactions. Moreover, we observe the persistent spin helix symmetry by gate tuning.

Acoustically induced spin-orbit interactions revealed by two-dimensional imaging of spin transport in GaAs.

Magneto-optic Kerr microscopy was employed to investigate the spin-orbit interactions of electrons traveling in semiconductor quantum wells using surface acoustic waves (SAWs). Two-dimensional images of the spin flow induced by SAWs exhibit anisotropic spin precession behaviors caused by the coexistence of different types of spin-orbit interactions. The dependence of spin-orbit effective magnetic fields on SAW intensity indicates the existence of acoustically controllable spin-orbit interactions resulting from the strain and Rashba contributions induced by the SAWs.

Predictors of outcome following myeloablative allo-SCT for therapy-related myelodysplastic syndrome and AML.

Administration of alkylating agents (Alk), topoisomerase II inhibitors (Topo II) and radiotherapy (RT) can result in therapy-related myelodysplastic syndrome or acute myelogenous leukaemia (t-MDS/t-AML), the optimal treatment for which is allo-SCT. A retrospective review was performed of 24 patients who underwent related- or unrelated-donor SCT for t-MDS/t-AML at our institution. Eight patients remain alive and in continuous remission (median follow-up 54 months (range, 12-161)) with estimated 5-year EFS being 30% (95% confidence intervals 16-58%). Corresponding actuarial risks of relapse and non-relapse mortality (NRM) are 39% (19-60%) and 30% (13-50%), respectively. EFS was 40% in Alk/RT-related t-MDS/t-AML and 11% in Topo II-related t-MDS/t-AML (P=0.05), with an increased risk of relapse in the latter (56 vs 29%, respectively (P=0.05)). In multivariate analysis, development of acute GVHD (P=0.009) and Topo II-related t-MDS/t-AML (P=0.018) were associated with inferior EFS. Patients with acute GVHD had an increased risk of NRM (P=0.03) whereas risk of relapse was higher for patients of advanced age (P=0.046) and for patients who underwent bone marrow (vs blood) SCT (P=0.032). Allo-SCT can result in long-term survival for individuals with t-MDS/t-AML although outcome in Topo II-related t-MDS/t-AML patients remains suboptimal.

Universal spin-induced time reversal symmetry breaking in two-dimensional electron gases with Rashba spin-orbit interaction.

We have experimentally studied the spin-induced time reversal symmetry (TRS) breaking as a function of the relative strength of the Zeeman energy (E(Z)) and the Rashba spin-orbit interaction energy (E(SOI)), in InGaAs-based 2D electron gases. We find that the TRS breaking, and hence the associated dephasing time tau(phi)(B), saturates when E(Z) becomes comparable to E(SOI). Moreover, we show that the spin-induced TRS breaking mechanism is a universal function of the ratio E(Z)/E(SOI), within the experimental accuracy.

Plate and screw technique for advancement of the supraorbital bar in surgery for craniosynostosis: a preliminary technical report.

An alternative plate and screw method of advancement of the supraorbital osteotomy bar in cranial remodelling surgery for craniosynostosis is described. The lateral orbital rim is transversely cut and using miniplates, screws are implanted into its advanced cut ends. Appropriate screws and miniplates are used to suit the size of the orbital rim in patients of different age groups. The technique was used in 12 cases and the authors have found the results extremely gratifying. It offered the advantage of providing a firm, secure and desired advancement, and height of the supraorbital bar maintaining a smooth lateral rim contour. The procedure was technically relatively straightforward. Further observation is warranted to determine whether the stabilization will last into adulthood or if there will be any problem related to the metal screws and plates.

Isocentric head fixation for microscopic neurosurgery.

The significance of isocentering in head fixation during micro-neurosurgery is described. The approach angle to the lesion could be changeable without adjusting the focus and placement of the operating microscope by rotating the head holder when the lesion is fixed at the isocenter of the rotatable.

Surgery on lesions involving cavernous sinus.

Selection of the operative route for cavernous sinus related lesions, the extent of the exposure necessary, the need for intraoperative control of the carotid artery and feasibility and need of radical resection depend on the histological nature of the tumour. The age and sex of the patient, principal presenting signs, size of the tumour, extent of cranial nerve and carotid artery involvement, imaging characters and other such features are helpful in estimating the consistency and vascularity of the lesion, site of origin and direction of its spread, and the extent and nature of cavernous sinus involvement. Evaluation of the histology of the lesion on the basis of the radiological and clinical parameters and the impact on decision regarding the surgical strategy is discussed in the present report.

Clinical characteristics of rapid atrial fibrillation preceding ventricular tachycardia.

Spontaneous degeneration of rapid atrial fibrillation (AF) to ventricular fibrillation has been documented in patients with hypertrophic cardiomyopathy (HCM) and Wolff-Parkinson-White (WPW) syndrome. However, the importance of rap

Atypical pleomorphic astrocytoma in the pineal gland: case report.

OBJECTIVE AND IMPORTANCE: We report a rare case of pleomorphic astrocytoma in the pineal region that took a benign course despite pleomorphism. CLINICAL PRESENTATION: A 30-year-old woman suddenly developed right hemiparesis followed by loss of consciousness. A computed tomographic scan revealed a mass in the pineal region accompanied by obstructive hydrocephalus. Her symptoms improved after ventriculoperitoneal shunt surgery. INTERVENTION: The tumor was totally removed in an en bloc fashion using the occipital interhemispheric transtentorial route. Light microscopy revealed that the tumor had marked pleomorphism and multinucleated, bizarre giant cells, but neither mitosis nor necrosis was seen. Glial fibrillary acid protein was immunohistochemically positive in a few tumor cells. Retinal soluble antigen was negative. No reticulin network between the tumor cells was observed. A histological diagnosis of atypical pleomorphic astrocytoma was made. CONCLUSION: No signs of recurrence have been observed for 7 years after surgery without adjuvant therapy. Histologically, the tumor resembled pleomorphic xanthoastrocytoma or pleomorphic granular cell astrocytoma, but the immunohistochemical findings were not completely compatible with either diagnosis. This benign astrocytoma in the pineal gland with unique features is the first such case reported.

Nonlinear ablation targeting an isthmus of critically slow conduction detected by high-density electroanatomical mapping for atypical atrial flutter.

Focused high-density atrial endocardial mapping was performed with a three-dimensional electroanatomical mapping system or a multielectrode basket catheter in six men and two women (mean age = 54 years) with atypical atrial flutter (AFL) to characterize its reentry circuit and identify its isthmus of critically slow conduction (ICSC). Activation mapping revealed figure-8 reentry with ICSC between a surgical atrial scars in three atypical AFLs following atriotomy, and between the crista terminalis (CT) and the inferior (IVC) or superior (SVC) vena cavae in atypical right atrial (RA) AFL in absence of prior atriotomy. Figure-8 double loop reentry was documented in one RA atypical AFL. ICSC was characterized by concealed entrainment with a post-pacing interval identical to the AFL cycle length, and a mid-diastolic fractionated electrogram, 129 +/- 23 ms in duration, spanning the isoelectric line between double potentials on adjacent area of conduction block. All AFLs were successfully ablated with 4.9 +/- 4.3 RF pulses applied at ICSC. A possible mechanism of atypical AFL consists of figure-8 reentry with ICSC between surgical scars in postoperative AFL, and between the CT and the IVC/SVC in RA AFL not preceded by cardiac surgery. Late and partial regeneration of conduction across the atriotomy scar can create an ICSC. Nonlinear ablation targeting ICSC can cure atypical AFL, whether it follows surgery or not.

A jump in cycle length of orthodromic common atrial flutter during catheter ablation at the isthmus between the inferior vena cava and tricuspid annulus; evidence of dual isthmus conduction directed to dual septal exits.

INTRODUCTION: In orthodromic common atrial flutter (AFL), details of intraseptal propagation of the flutter (FL) wave exiting from the isthmus between the inferior vena cava and tricuspid annulus (IVC-TA isthmus) remain unknown. We hypothesized the existence of dual septal exits of the FL wave from the IVC-TA isthmus to both the anterior, coronary sinus ostium (CSO-TA) isthmus, and the posterior septal (IVC-CSO) isthmus, and that the IVC-TA isthmus might consist of dual muscle bundles directed to both septal isthmuses over the eustachian ridge; therefore, segmental ablation of the IVC-TA isthmus could change intraseptal FL wave propagation. METHODS AND RESULTS: To test the hypothesis, we investigated the influence of segmental ablation of the IVC-TA isthmus on intraseptal FL wave propagation. In seven of 40 (18%) consecutive patients, segmental ablation of the ventricular side of the IVC-TA isthmus during orthodromic common AFL led to sudden prolongation of the flutter cycle length (FCL) (from 266 +/- 33 ms to 291 +/- 45 ms) associated with changes in intraseptal activation sequences. They consisted of prolongation of the interval between the IVC-TA isthmus and the CSO (from 38 +/- 13 ms to 86 +/- 25 ms), shortening of the interval between the CSO and His (from 31 +/- 15 ms to 9 +/- 15 ms), and atrial electrogram polarity change at the His-bundle recording site. Morphological change in the FL wave was also seen on the 12-lead ECG. CONCLUSIONS: In some patients, segmental ablation of the IVC-TA isthmus can lead to a jump in FCL and changes in intraseptal activation sequences of FL waves due to anterior-to-posterior shifting of the septal exit. This indicates that the IVC-TA isthmus may contain dual circumferential muscle bundles as conduction pathways directed to dual septal exits both anterior and posterior to the CSO.

Anchoring method for hemifacial spasm associated with vertebral artery: technical note.

OBJECTIVE: We describe an easy and useful method for treating hemifacial spasm related to the vertebral artery. METHODS: The technique entails the manufacture of a dural belt harvested from the cerebellar convexity dura and a dural bridge made at the petrous dura combined with the use of an aneurysm clip. The dural belt holds the vertebral artery and is anchored to the dural bridge by fixation with an aneurysm clip after the vertebral artery is transposed to an appropriate position. RESULTS: The technique proved to be safe and effective in a series of six patients with hemifacial spasm who were followed up for a period of 2 months to more than 10 years after surgery. All patients were affected on the left side. Multiple offending arteries were present in three cases. Hemifacial spasm completely disappeared in all patients. CONCLUSION: This method represents a feasible option for the treatment of hemifacial spasm caused by a tortuous, elongated, or enlarged vertebral artery.

Radiofrequency catheter ablation for sinoatrial node reentrant tachycardia: electrophysiologic features of ablation sites.

The aim of this study was to investigate catheter ablation of sino-atrial reentrant tachycardia (SART) and the electrophysiologic characteristics of the ablation sites. From January 1990 to October 1997, 651 patients with supraventricular tachycardia were referred and 11 patients were found to have SART. Ablation was successful in all cases with a mean number of 3.3 radiofrequency (RF) current pulses. SART terminated during 22 of 36 RF pulses. In spite of prompt termination, tachycardia could be re-induced in 3 of 11 patients with its earliest activation site shifted. At effective ablation sites, the electrograms during tachycardia were characterized as fractionated (75+/-17 ms), and 38+/-16 ms prior to surface P wave, and 42+/-18 ms prior to the high right atrium. Unipolar electrograms revealed a sharp negative unipolar deflection, so called QS pattern, in 15 of 20 sites during SART and 15 of 15 sites during sinus rhythm. During effective applications, atrial premature beats (APB) with activation sequences identical to sinus rhythm appeared in 14 of 22 cases. Effective ablation sites of SART showed fractionated electrograms during tachycardia and sinus rhythm. Unipolar electrogram with a QS pattern and APB during energy application could be an indicator of the optimal ablation sites.

Clinical analysis of internal carotid artery aneurysms with reference to classification and clipping techniques.

An intraoperative classification of intradural internal carotid artery (ICA) aneurysms not related to the arterial division but based on their operative presentation and clipping techniques is introduced. On the basis of the surgeon's view of the operative field via the pterional approach in 156 operated intradural ICA aneurysms in 143 patients, these aneurysms were classified according to their location in relation to the long axis of the ICA as either proximal, middle or distal in type and also according to their relation to the cross section of the ICA as either lateral, medial, ventral or dorsal in type. Numerically the largest in frequency is the middle type of aneurysm by axial location and the lateral type of aneurysms by cross sectional location. Eighty five percent of the lateral type aneurysms were at the arterial division. The majority of the large to giant aneurysms were of the ventral type and no dorsal type aneurysms were seen. About one third of the ICA aneurysms in this series were located free of the arterial division. All dorsal type aneurysms and most of the medial type aneurysms were not related to the arterial division. Clipping techniques were classified into perpendicular and parallel clipping, as to the direction of the clip-blades in relation to the carotid axis. The parallel clipping was further classified into forward clipping, in which a clip was applied from the distal side of the ICA, and reversed clipping, in which a clip was applied from the proximal side of the ICA. Most of the aneurysms located at the arterial division required the perpendicular clipping and those free of the arterial division required the parallel clipping. Furthermore, the forward clipping was useful for proximal type aneurysms and the reversed clipping for distal type aneurysms. For the middle type aneurysms clipping was performed bidirectionally. This classification includes all types of the ICA aneurysms located at any points along its long axis and on its cross section, and is useful for planning safe and exact clipping of the ICA aneurysms.

Color Doppler ultrasound imaging in the emergency management of an intracerebral hematoma caused by cerebral arteriovenous malformations: technical case report.

OBJECTIVE AND IMPORTANCE: Ruptured arteriovenous malformations (AVMs) are important causes of spontaneous intracerebral hemorrhages. This is a report of emergency hematoma removal, avoiding damage to the nidus of the AVM, using intraoperative color Doppler imaging. CLINICAL PRESENTATION: A 38-year-old woman suddenly presented with coma. The patient underwent emergency surgery immediately after admission, without preoperative angiographic examination, because of progressive neurological deterioration caused by a massive hematoma in the right basal ganglia, as diagnosed with computed tomographic scanning. INTERVENTION: A right frontotemporoparietal craniotomy was performed. Intraoperative ultrasound imaging with a color Doppler system (EUP-NS32, 5 MHz; Hitachi Medical, Tokyo, Japan) clearly demonstrated a nidus complex in the hematoma. Based on the imaging, effective decompression of the hematoma was performed without damage to the AVM complex. CONCLUSION: Color Doppler imaging (with real-time availability) of an atypical hematoma provided significant information on the vascular lesion causing the hematoma and could reduce the surgical risks during emergency evacuation of large intracerebral hemorrhages resulting from ruptured AVMs.

High energy radiofrequency catheter ablation for common atrial flutter targeting the isthmus between the inferior vena cava and tricuspid valve annulus using a super long tip electrode.

There have been controversies concerning the optimal target sites and approaches in radiofrequency catheter ablation of common atrial flutter. We attempted high energy radiofrequency catheter ablation targeting the isthmus between the inferior vena cava and tricuspid valve annulus (IVC-TV isthmus) with a super long (8 mm) tip electrode, and compared the efficacy of this anatomical approach with the electrophysiological approach targeting the posteroseptal right atrium posterior to the coronary sinus using a standard 4-mm tip electrode. Atrial flutter was successfully ablated in 12 of 12 patients (100%) without recurrence with the anatomical approach, while, in 7 of 9 patients (64%) with 2 recurrences with the electrophysiological approach. In comparison of ablation data between the anatomical and electrophysiological approaches, there were significant differences in the mean number of application pulses (anatomical vs electrophysiological: 2.3 +/- 0.8 vs 9.9 +/- 6.4, P < 0.01), applied wattage (39 +/- 12 W vs 24 +/- 6 W, P < 0.01), applied energy per application (1,986 +/- 426 J vs 659 +/- 323 J, P < 0.01), fluoroscopic time (26 +/- 11 min vs 74 +/- 30 minutes, P < 0.01), and procedure time (59 +/- 8 min vs 181 +/- 53 min, P < 0.01). In conclusion, the anatomical approach is superior to the electrophysiological one with respect to procedure and radiation time, and linear ablation at the IVC-TV isthmus with an 8-mm tip electrode and high energy application is highly effective and safe.

Ultramicroscopic structures of the leptomeninx of mice with communicating hydrocephalus induced by human recombinant transforming growth factor-beta 1.

An experimental model of communicating hydrocephalus was developed based on intrathecal injection of human recombinant transforming growth factor-beta 1 (hrTGF-beta 1) in the mouse. To clarify the mechanism of this hydrocephalus model, the ultrastructure of the leptomeninx in the process of ventricular dilation was examined in C57/BL6 mice injected intrathecally with 60 ng of hrTGF-beta 1. The leptomeninx was examined at various periods after injection by light and electron microscopy. Immunostaining for fibroblasts and macrophages was also performed. Leptomeninx within a week after injection showed that the thin cytoplasmic processes of leptomeningeal cells formed a laminated structure with a meshwork, which was almost the same as the controls. In the second week, many cells with a round nucleus appeared in the leptomeninx. Immunohistochemically, these cells were positive for anti-fibroblast antibody and negative for anti-Mac-1 and anti-macrophage BM-8 antibodies. Three weeks later, the laminated structure was disrupted and abundant deposition of collagen fibers was found in the inter-cellular space of the leptomeninx. Such inter-meningeal fibrosis would disturb cerebrospinal fluid flow in the mouse leptomeninx and cause slowly progressive ventricular dilation.