Algebraic solution for a two-level atom in radiation fields and the Freeman resonances

Journal ArticleUsing techniques of complex analysis in an algebraic approach, we solve the wave equation for a two-level atom interacting with a monochromatic light field exactly. A closed-form expression for the quasienergies is obtained, which shows that the Bloch-Siegert shift is always finite, regardless of whether the original or the shifted level spacing is an integral multiple of the driving frequency ω. We also find that the wave functions, though finite when the original level spacing is an integral multiple of ω, become divergent when the intensity-dependent shifted energy spacing is an integral multiple of the photon energy. This result provides an ab initio theoretical explanation for the occurrence of the Freeman resonances observed in above-threshold ionization experiments

Suppression of local degrees of freedom of gauge fields by chiral anomalies

Journal ArticleA path-integral quantization is presented for the chiral Schwinger model on a Riemann surface. Gauge invariance is maintained by integrating over all gauge potentials without the usual gauge fixing. All local degrees of freedom of the gauge field are suppressed after the integration of the anomalous effective action over a gauge orbit. The resulting theory is a topological one for the surviving global gauge excitations. The general implications for consistent quantization of chiral gauge theories are also discussed

High-precision quasienergies for a driven two-level atom at the two-photon preresonance

Journal ArticleA computation with unprecedented precision is presented for quasienergies of a two-level atom in a monochromatic radiation on the basis of a recently obtained exact expression [D.-S. Guo et al., Phys. Rev. A 73,023419 (2006)]. We start with the proof of an expression theorem. With this theorem the quasienergies for any two-level atom can be expressed in terms of the quasienergies for only those with the original energy spacing (per field photon energy) being an integer (preresonances). Then we carry out a numerical evaluation of the quasienergies at the two-photon preresonance, which involves computing an infinite determinant, up to the 18th power of the coupling strength. The theoretical prediction presents an experimental challenge for highprecision tests of quantum mechanics and could be exploited for precise calibration of high laser intensities

Hemiplegia as a special form of recurrent glioma pathogenesis: analysis of 1 cases

目的  探讨复发性神经胶质瘤的临床、影像学特征及诊治方法。方法  回顾性分析1例复发性神经胶质瘤的诊治过程，并复习有关文献。结果  该患者以突发特殊形式偏瘫为唯一症状起病，上肢屈曲旋前，下肢伸直内收，酷似卒中；头颅电子计算机断层扫描(CT)示右额颞叶占位病变，周围有不规则水肿带形成；术后病理检查示多形性胶质母细胞瘤。结论  复发性神经胶质瘤约80%的复发病灶位于其原发灶周围2cm处，临床表现及影像学检查无特异性，常规CT与磁共振成像（MRI）检查一般对肿瘤是否复发以及确定肿瘤侵犯范围等方面具有局限性，很难区别肿瘤复发、放射性脑损伤或肿瘤假性进展，诊断主要依靠术后病理检查，手术是目前主要的治疗方法，术后可辅以放射治疗、化学治疗以及生物学治疗，但预后较差。Objective: To explore of the clinical and radiographic characteristics, methods of diagnosis and treatment of recurrent glioma. Methods: To retrospectively analyze the diagnostic and treatment process of 1 case of recurrent glioma patients, and to have literature review. Result: The patients with hemiplegia burst special form as the only symptom onset, upper limb flexion pronation, straight leg adduction, and stroke are very similar. Her head computed tomography (CT) showed right frontotemporal lobar lesions, irregular with edema formation around. Her postoperative pathologic examination revealed a glioblastoma multiforme. Conclusions: Recurrence lesions of glioma were located 2 cm away around the primary tumors in 80 percent of the cases. There were no clinical manifestations and specific neuroimaging regarding the disease. Conventional CT and magnetic resonance imaging (MRI) examination in general has limitations on tumor recurrence,( tumor extent and other aspects, it is difficult to distinguish the progress of tumor recurrence and radiation brain injury or tumor pseudo progression. The disease diagnosis mainly depends on the pathological examination after operation. Operation is currently the main disease treatment, postoperative radiotherapy, treatment can be supplemented with chemical and biological therapy, but the prognosis is poor