Visible-Light-Mediated TiO2-Catalyzed Aerobic Dehydrogenation of N-Heterocycles in Batch and Flow.

We report a simple and environmentally friendly method for synthesizing N-containing heterocycles via a visible-light-mediated aerobic dehydrogenation reaction. Using a nontoxic, stable, and inexpensive titanium dioxide catalyst, a variety of substituted quinoline, indole, quinoxaline, and 3,4-dihydroisoquinoline derivatives could be synthesized using the green oxidant molecular oxygen. Improved reactivity and scalability of this reaction were demonstrated by adapting the photochemical multiphasic reaction to a continuous flow system. To gain insight into the mechanism, we also conducted several mechanistic studies, including absorption analysis, light on-off testing, and NMR analysis. Especially, oxygen is reduced to hydrogen peroxide, and dimethyl sulfoxide is a critical scavenger of the oxidant byproduct for ensuring high yields.

A Capacitive Feedback Transimpedance Amplifier with a DC Feedback Loop Using a Transistor for High DC Dynamic Range.

This study proposes a capacitive feedback transimpedance amplifier (CF-TIA) using a transistor in the direct current (DC) feedback loop for high DC dynamic range. In some applications, the background DC input can vary widely from the minimum to the maximum, and TIA have to sense the target signal even on the top of the maximum DC input. In a conventional CF-TIA, however, the allowable DC input is constrained by the value of the resistor in the DC feedback loop. To allow a fairly high DC input, the resistor is set to a very low value. This causes the thermal noise current to increase significantly. The increased thermal noise is always present even in the minimum DC input, thus degrading the overall noise performance. The circuit proposed herein overcomes this shortcoming by using the transistor instead of the resistor. The adverse effect of the parasitic capacitance of the transistor on system stability is compensated for as well. Then, the analyses of the overall frequency response and design parameters, including the cut-off frequency and attenuation ratio associated with system stability, are presented for the proposed circuit. In addition, in order to cope with the problem that stability is dependent on the amount of DC input, a simple method for ensuring system stability regardless of DC component value is introduced. The presented analyses and the method are generalized for all CF-TIA applications.

Optimal treatment of leptomeningeal spread in glioblastoma: analysis of risk factors and outcome.

BACKGROUND: Glioblastoma (GBM) is the most common and malignant brain tumor in adults. Despite therapeutic advances, almost all patients eventually experience tumor recurrence. Leptomeningeal spread (LMS) is not a rare condition of recurrence. However, the standard management protocol of LMS has not been established. The aim of this study is to report the risk of (LMS) and the prognosis between treatment modalities in GBM patients. METHODS: A retrospective review was conducted of 321 patients who were diagnosed with GBM between January 2006 and December 2010. In 75 patients, LMS of tumor was detected by magnetic resonance image and/or cerebrospinal fluid cytology. Twelve patients underwent intrathecal methotrexate (IT-MTX) chemotherapy. Twenty-two patients underwent other salvage treatments. Forty-one patients underwent conservative management. We analyzed the possible clinical factors for LMS. Further, we examined overall survival and survival after diagnosis of LMS for several treatment modalities. RESULTS: In patients without LMS, median overall survival was 479 days, whereas that in patients with LMS it was 401 days. Younger age and larger initial tumor size were related to more frequent LMS incidence. Proximity between tumor margin and ventricle did not affect LMS. However, median duration from initial diagnosis to LMS was significantly different according to the distance to the ventricle. IT-MTX group's overall survival was 583 days, which is statistically no longer than that of the other treatment group and the conservative management group. However, an additional survival benefit may exist compared to the conservative treatment. The median survival of the IT-MTX group was 181 days compared with 91 days for the conservative management group. CONCLUSIONS: Treatment of LMS is mainly palliative. IT-MTX is generally the first-line treatment modality of LMS. Prediction and prevention of LMS is crucial because its treatment has been limited. Further approaches to improve the therapeutic effect should be established.

Microsurgical treatment and outcome of pediatric supratentorial cerebral cavernous malformation.

OBJECTIVE: The purpose of this study was to investigate the clinical features and outcomes of pediatric cavernous malformation (CM) in the central nervous system. METHODS: Twenty-nine pediatric patients with supratentorial CM underwent microsurgical excision. In selected cases, transparent tubular retractor system (TTRS) was used to reduce retraction injury and intraoperative neuromonitoring (IONM) was held to preserve functioning cortex. Patients' demographics and symptoms were reviewed and surgical outcomes were discussed. RESULTS: THE MAIN INITIAL CLINICAL MANIFESTATIONS INCLUDED THE FOLLOWING : seizures (n=13, 45%), headache (n=7, 24%), focal neurological deficits (n=3, 10%), and an incidental finding (n=6, 21%). Overt hemorrhage was detected in 7 patients (24%). There were 19 children (66%) with a single CM and 10 (34%) children with multiple CMs. In 7 cases with deep-seated CM, we used a TTRS to minimize retraction. In 9 cases which location of CM was at eloquent area, IONM was taken during surgery. There was no major morbidity or mortality after surgery. In the 29 operated children, the overall long-term results were satisfactory : 25 (86%) patients had no signs or symptoms associated with CMs, 3 had controllable seizures, and 1 had mild weakness. CONCLUSION: With the assistance of neuronavigation systems, intraoperative neuromonitoring, and TTRS, CMs could be targeted more accurately and excised more safely. Based on the satisfactory seizure outcome achieved, complete microsurgical excision in children is recommended for CMs presenting with seizures but removal of hemosiderin-stained areas seems to be unnecessary.

Endoscopic Decompression for Optic Neuropathy in McCune-Albright Syndrome.

McCune-Albright syndrome (MAS) is characterized by a triad of poly/monostotic fibrous dysplasia, café-au-lait macules and hyperfunctioning endocrinopathies including human growth hormone excess. Acromegaly as a manifestation of endocrine hyperfunction with MAS is uncommon. Surgical excision may be challenging due to the associated severe fibrous dysplasia of the skull base. Through the endoscopic procedures, we treated a case of MAS presenting with compressive optic neuropathy due to fibrous dysplasia and acromegaly caused by growth hormone secreting pituitary adenoma. We reviewed the literature on GH excess in MAS to highlight its surgical and medical challenges.

Cerebral arteriovenous malformation associated with moyamoya disease.

The coexistence of moyamoya disease (MMD) with an arteriovenous malformation (AVM) is exceedingly rare. We report two cases of AVM associated with MMD. The first case was an incidental AVM diagnosed simultaneously with MMD. This AVM was managed expectantly after encephalo-duro-arterio-synangiosis (EDAS) as the main feeders stemmed from the internal carotid artery, which we believed would be obliterated with the progression of MMD. However, the AVM persisted with replacement of the internal carotid artery feeders by new external carotid artery feeders from the EDAS site. The AVM was eventually treated with gamma knife radiosurgery considering an increasing steal effect. The second case was a de novo AVM case. The patient was initially diagnosed with MMD, and acquired an AVM eight years later that was slowly fed by the reconstituted anterior cerebral artery. Because the patient remained asymptomatic, the AVM is currently being closely followed for more than 2 years without further surgical intervention. Possible differences in the pathogenesis and the radiologic presentation of these AVMs are discussed with a literature review. No solid consensus exists on the optimal treatment of MMD-associated AVMs. Gamma knife radiosurgery appears to be an effective treatment option for an incidental AVM. However, a de novo AVM may be managed expectantly considering the possible risks of damaging established collaterals, low flow characteristics, and probably low risks of rupture.