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The generation mechanism of a diffuser stall in a centrifugal compressor with a vaneless diffuser was investigated by experimental and computational analyses. The diffuser stall generated as the mass flow rate decreased. The diffuser stall cell rotated at 25-30 % of the impeller rotational speed, with diffuser stall fluctuations observed at 180° from the cutoff. The diffuser stall fluctuation magnitude gradually increased near the cutoff. According to the CFD analysis, the mass flow fluctuations at the diffuser exit showed a low mass flow region, rotating at approximately 25% of the impeller rotational speed. They began at 180° from the cutoff and developed as this region approached the cutoff. Therefore, the diffuser stall could be simulated by CFD analysis. First, the diffuser stall cell originated at 180° from the cutoff by interaction with boundary separation and impeller discharge vortex. Then, the diffuser stall cell further developed by boundary separation accumulation and the induced low velocity area The low velocity region formed a blockage across the diffuser passage span. The diffuser stall cell expanded due to boundary separation caused by a positive flow angle. Finally, the diffuser stall cell vanished when it passed the cutoff, because mass flow recovery occurred.

The effect of diffuser width on the noise level of a centrifugal compressor equipped with vaneless diffusers was investigated through experiments and numerical techniques. In this regard, two diffusers with different widths were installed in the compressor. In case the wider diffuser was used, there was the bandwidth (800 to 900 Hz) noise and pressure fluctuation which was closed to 1/2BPF (700 Hz). This fluctuation occurred because the leakage vortices were of two different frequencies. Type 1 vortices are the ones that were discharged from the main blade and covered Passage 1. Type 2 vortices had the same length as Type 1, but they were discharged from the splitter blade. Type 3 vortices covered both Passages 1 and 2; these were discharged from the main blade. Type 3 vortices were generated predominantly at 270°, and their frequency was approximately 700 Hz at 1/2 BPF frequency. The former two types of vortices occurred occasionally, and their frequency was approximately 1400 Hz. Type 3 vortices grew with the wider diffuser because of the higher pressure-recovery, which caused the serous loading to the impeller blades. The broadband noise fluctuation occurred by the coexistence of the two frequency vortices.

Summary Sarcoidosis is a multisystem disorder of unknown aetiology, which presents with hilar lymphadenopathy, pulmonary infiltration, and ocular and cutaneous involvement. Cutaneous lesions often present as erythema nodosum, maculopapular, plaque, scar, subcutaneous nodule or lupus pernio. Most patients with cutaneous involvement have a single type of skin lesion, but some cases may have ≥ 2 types. We report a case of sarcoidosis presenting with various types of skin lesions. The case was also complicated by hypercalcaemia and renal dysfunction, and was successfully treated with oral corticosteroids. Presentation of various skin lesions may indicate systemic organ involvement requiring treatment with systemic corticosteroid.

We report a case of malignant peripheral nerve sheath tumor (MPNST) of the nape. A 52-year-old woman suffering from neurofibromatosis type I since her childhood noticed a tumor on the nape six years ago. The tumor gradually became enlarged and elevated. On her visit to our hospital on July 25th, 2002, physical examination revealed an elastic soft, 15×13×6cm sized tumor on the left side of her nape. The tumor grew rapidly and ruptured with bleeding on August 23rd. Immediate excision of the tumor was performed. Histologically, the tumor mainly consisted of spindle cells showing palisading arrangement.A part of the specimen showed nuclear atypia and mitoses. Immunohistochemically, the spindle cells were positive for S-100 protein and NSE. The tumor was diagnosed as MPNST. Multiple lung and liver metastases developed and the patient died of respiratory failure caused by lung metastases in 5 months after her first visit to our institution. [Skin Cancer (Japan) 2004; 19: 229-232]

We report a 58-year-old woman with bronchial asthma. The onset of the disease was marked by numbness in the right lower extremity, for which she was hospitalized 10 days later. The patient presented with sensory impairment and muscle weakness in the distal regions of both lower limbs, acute pain, purpura, and a leukocyte count of 2.4 × 10(4)/μl (59.2% eosinophils). Nerve conduction tests revealed a decrease in the amplitude of the compound muscle action potential in all 4 extremities. Skin biopsy results led to the diagnosis of eosinophilic granulomatosis with polyangiitis (EGPA). Steroid pulse therapy and oral steroid therapy were initiated but did not resolve the acute pain or numbness. However, intravenous immunoglobulin (IVIg) was administered at day 28 after the beginning of the steroid treatment, and the pain started to improve immediately afterward. In some cases, IVIg can be effective in the treatment of intense pain in peripheral neuropathy associated with steroid-resistant EGPA.

Summary Background. Corticosteroids, especially prednisolone or prednisone, are the most commonly used drugs for the treatment of bullous pemphigoid (BP). However, the appropriate initial effective prednisolone dose has not been established. Recently, a highly sensitive and specific ELISA for detection of autoantibodies to the non-collagenous extracellular domain (NC16A) of the 180 kDa transmembrane hemidesmosome component [bullous pemphigoid (BP)180] was developed, and the titre of anti-BP180 antibody was found to be closely related to disease activity. Aim. To investigate the relationship between anti-BP180 antibody titre and effective prednisolone dose alone or in conjunction with other immunosuppressants. Methods. Anti-BP180 antibody titres were measured by ELISA for the NC16A domain of BP180 in the sera of patients with BP (n = 42) at the start of treatment. The effective prednisolone dose was calculated from the patients’ records. Results. Higher anti-BP180 antibody titres correlated with a higher effective prednisolone dose. In particular, patients with antibody titres > 200 required a significantly higher effective prednisolone dose than did those with antibody titres ≤ 200. Conclusions. A higher effective prednisolone dose may be necessary for patients who have both a high titre of anti-BP180 antibody and severe clinical disease.

Paraneoplastic pemphigus (PNP) is an autoimmune mucocutaneous disease, associated with neoplasia, which has characteristic clinical, histological and immunological features. While respiratory epithelial involvement has been described in several cases, lesions in the colon epithelium have never been reported. We describe a 57-year-old Japanese woman with PNP who had many aphthae-like erosions on the colon epithelium, in addition to typical mucocutaneous PNP lesions. The intestinal erosions had histological features similar to those of PNP and linear deposition of complement, but not IgG, was observed along the colon epithelial basement membrane.