Growth of III-V films by control of MBE growth front stoichiometry

For the growth of strain-layer materials and high quality single and multiple quantum wells, the instantaneous control of growth front stoichiometry is critical. The process of the invention adjusts the offset or phase of molecular beam epitaxy (MBE) control shutters to program the instantaneous arrival or flux rate of In and As4 reactants to grow InAs. The interrupted growth of first In, then As4, is also a key feature

MBE growth technology for high quality strained III-V layers

The III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group III and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation of low temperature, and to permit the film to relax to equilibrium. The method of the invention: (1) minimizes starting step density on sample surface; (2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 monolayers at a time); (3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and (4) uses time-resolved RHEED to achieve aspects (1) through (3)

Lithium alters expression of RNAs in a type-specific manner in differentiated human neuroblastoma neuronal cultures, including specific genes involved in Alzheimer's disease.

Lithium (Li) is a medication long-used to treat bipolar disorder. It is currently under investigation for multiple nervous system disorders, including Alzheimer's disease (AD). While perturbation of RNA levels by Li has been previously reported, its effects on the whole transcriptome has been given little attention. We, therefore, sought to determine comprehensive effects of Li treatment on RNA levels. We cultured and differentiated human neuroblastoma (SK-N-SH) cells to neuronal cells with all-trans retinoic acid (ATRA). We exposed cultures for one week to lithium chloride or distilled water, extracted total RNA, depleted ribosomal RNA and performed whole-transcriptome RT-sequencing. We analyzed results by RNA length and type. We further analyzed expression and protein interaction networks between selected Li-altered protein-coding RNAs and common AD-associated gene products. Lithium changed expression of RNAs in both non-specific (inverse to sequence length) and specific (according to RNA type) fashions. The non-coding small nucleolar RNAs (snoRNAs) were subject to the greatest length-adjusted Li influence. When RNA length effects were taken into account, microRNAs as a group were significantly less likely to have had levels altered by Li treatment. Notably, several Li-influenced protein-coding RNAs were co-expressed or produced proteins that interacted with several common AD-associated genes and proteins. Lithium's modification of RNA levels depends on both RNA length and type. Li activity on snoRNA levels may pertain to bipolar disorders while Li modification of protein coding RNAs may be relevant to AD

Frequency invariant beamforming for two-dimensional and three-dimensional arrays

A novel method for the design of two-dimensional (2-D) and three-dimensional (3-D)arrays with frequency invariant beam patterns is proposed. By suitable substitu- tions, the beam pattern of a 2-D or 3-D arrays can be regarded as the 3-D or 4-D Fourier transform of its spatial and temporal parameters. Since frequency invariance can be easily imposed in the Fourier domain, a simple design method is derived. Design examples for the 2-D case are provided

Efficacy of multiple intraarterial papaverine infusions for improvement in cerebral circulation time in patients with recurrent cerebral vasospasm

Journal ArticleObject. Cerebral vasospasm that is caused by aneurysmal subarachnoid hemorrhage and that is refractory to maximal medical management can be treated with selective intraarterial papaverine infusions. The effects of single papaverine treatments on cerebral circulation time are well known. The purpose of this study was to assess the efficacy of multiple, repeated papaverine infusions on the cerebral circulation time in patients with recurrent vasospasm. Methods. A retrospective study was conducted in 17 patients who received multiple intraarterial papaverine infusions in 91 carotid artery (CA) territories for the treatment of cerebral vasospasm. Cerebral circulation times were measured from the first angiographic image, in which peak contrast was seen above the supraclinoid internal CA, to the peak filling of cortical veins. Glasgow Outcome Scale (GOS) scores assessed 12 months after discharge were reviewed. Cerebral circulation times in 16 CA territories were measured in a control group of 11 patients. Seventeen patients received a total of 91 papaverine treatments. Prolonged cerebral circulation times improved after 90 (99%) of 91 papaverine treatments. The prepapaverine mean cerebral circulation time was 6.54 seconds (range 3.35-27 seconds) and the immediate postpapaverine mean cerebral circulation time was 4.19 seconds (range 2.1-12.6 seconds), an overall mean decrease of 2.35 seconds (36%, p <0.001). Recurrent vasospasm reflected by prolonged cerebral circulation times continued to improve with subsequent papaverine infusions. Repeated infusions were just as successful quantitatively as the primary treatment (mean change 2.06 seconds). The mean cerebral circulation time in the control group was 5.21 seconds (range 4-6.8 seconds). In five patients a dramatic reversal of low-attenuation changes was detected on computerized tomography scans. The mean GOS score at 12 months after discharge was 3.4. Conclusions. The preliminary results indicate that multiple intraarterial papaverine treatments consistently improve cerebral circulation times, even with repeated infusions in cases of recurrent vasospasm

Noncommunicating spinal extradural arachnoid cyst causing spinal cord compression in a child

Journal ArticleExtradural arachnoid cysts in the spine are relatively uncommon causes of spinal cord compression in the pediatric population that are thought to arise from congenital defects in the dura mater. Most reports describe such cysts communicating with the intrathecal subarachnoid space through a small defect in the dura. The authors describe the case of a child who presented with spinal cord compression caused by a large spinal extradural arachnoid cyst that did not communicate with the intradural subarachnoid space. An 11-year-old girl presented with urinary urgency, progressive lower-extremity weakness, myelopathy, and severe gait ataxia. Magnetic resonance imaging of the spine demonstrated a large extradural arachnoid cyst extending from T-8 to T-12. The patient underwent a thoracic laminoplasty for en bloc resection of the spinal extradural arachnoid cyst. Intraoperatively, the dura was intact and there was no evidence of communication into the intradural subarachnoid space. Postoperatively, the patient's motor strength and ambulation improved immediately, and no subsequent cerebrospinal fluid leak occurred. Noncommunicating spinal extradural arachnoid cysts are extremely rare lesions that can cause spinal cord compression in children. Because the dura remains intact, they can be removed entirely without subsequent dural repair. The authors review the literature and discuss the proposed underlying mechanisms of formation of these arachnoid cysts

Cranial base strategies for resection of craniopharyngioma in children

Journal ArticleThe optimal treatment of craniopharyngioma in children remains a challenge. The use of complete excision to minimize recurrence continues to be controversial because of the risk of postoperative morbidity and death. Advances in skull base approaches, modern microsurgical techniques, neuroimaging, and hormone replacement therapy, however, have allowed safe gross- or near-total resection in the majority of cases. Total removal of these tumors, if possible, offers the best chance of cure for the patient. Although craniopharyngiomas are not strictly tumors of skull base origin, their intimate relationship with the neurovascular structures of this region often requires a skull base approach to maximize the surgical corridor and facilitate adequate microsurgical resection. In this review, the authors focus on commonly used skull base approaches for the surgical management of craniopharyngioma. They discuss the relative indications, advantages, disadvantages, and complications associated with each approach. Illustrative cases and intraoperative videos are presented

Does the form of state ownership and political connections influence the incidence of financial statement fraud?

Do forms of state ownership and politically connected senior management affect the incidence of financial statement fraud? In this study, we consider these questions and provide new evidence as to the factors influencing fraud commission and detection for Chinese listed firms between 2007 and 2018. Six major types of financial statement fraud activities are identified. Using a bivariate probit model, developed to address partial observability concerns, we report state ownership lowers the likelihood of fraud detection, while increasing a firms’ propensity to commit fraud. In addition, state-owned enterprises (SOEs) controlled by local government are more likely to engage in fraud and escape regulatory punishments, relative to SOEs controlled by central government. The effect of politically connected senior management over fraud commission or regulatory detection is also diluted by the presence of state ownership. Moreover, the role of state ownership in encouraging fraud commissions and escaping from regulatory punishments is more pronounced for the local non-politically connected SOEs

Does the form of state ownership and political connections influence the incidence of financial statement fraud?

Do forms of state ownership and politically connected senior management affect the incidence of financial statement fraud? In this study, we consider these questions and provide new evidence as to the factors influencing fraud commission and detection for Chinese listed firms between 2007 and 2018. Six major types of financial statement fraud activities are identified. Using a bivariate probit model, developed to address partial observability concerns, we report state ownership lowers the likelihood of fraud detection, while increasing a firms’ propensity to commit fraud. In addition, state-owned enterprises (SOEs) controlled by local government are more likely to engage in fraud and escape regulatory punishments, relative to SOEs controlled by central government. The effect of politically connected senior management over fraud commission or regulatory detection is also diluted by the presence of state ownership. Moreover, the role of state ownership in encouraging fraud commissions and escaping from regulatory punishments is more pronounced for the local non-politically connected SOEs