Stick-slip behaviour on Au(111) with adsorption of copper and sulfate.

Several transitions in the friction coefficient with increasing load are found on Au(111) in sulfuric acid electrolyte containing Cu ions when a monolayer (or submonolayer) of Cu is adsorbed. At the corresponding normal loads, a transition to double or multiple slips in stick-slip friction is observed. The stick length in this case corresponds to multiples of the lattice distance of the adsorbed sulfate, which is adsorbed in a √3 × âˆš7 superstructure on the copper monolayer. Stick-slip behaviour for the copper monolayer as well as for 2/3 coverage can be observed at F N ≥ 15 nN. At this normal load, a change from a small to a large friction coefficient occurs. This leads to the interpretation that the tip penetrates the electrochemical double layer at this point. At the potential (or point) of zero charge (pzc), stick-slip resolution persists at all normal forces investigated.

Occurrence of lymph node metastasis in early-stage parotid gland cancer.

Lymph node metastasis is one of the most important factors in therapy and prognosis for patients with parotid gland cancer. Nevertheless, the extent of the primary tumor resection and the necessity of a neck dissection still is a common issue. Since little is known about lymph node metastasis in early-stage parotid gland cancer, the purpose of the present study was to evaluate the occurrence of lymph node metastases in T1 and T2 carcinomas and its impact on local control and survival. We retrospectively analyzed 70 patients with early-stage (T1 and T2) primary parotid gland cancer. All patients were treated with parotidectomy and an ipsilateral neck dissection from 1987 to 2009. Clinicopathological and survival parameters were calculated. The median follow-up time was 51.7 months. A positive pathological lymph node stage (pN+) was found in 21.4% of patients with a significant correlation to the clinical lymph node stage (cN) (p = 0.061). There were no differences in the clinical and histopathological data between pN- and pN+ patients. In 73.3% of pN+ patients, the metastases were located intraparotideal. The incidence of occult metastases (pN+/cN-) was 17.2%. Of all patients with occult metastases, 30.0% had extraparotideal lymphatic spread. A positive lymph node stage significantly indicated a poorer 5-year overall as well as 5-year disease-free survival rate compared to pN- patients (p = 0.048; p = 0.011). We propose total parotidectomy in combination with at least a level II-III selective neck dissection in any case of early-stage parotid gland cancer.

Prognostic value of proliferating cell nuclear antigen in parotid gland cancer.

Although cell proliferation is related to tumour aggressiveness and prognosis, there are few studies describing the expression of proliferative markers in salivary gland cancer. Our aim was to assess the long-term prognostic value of the proliferating cell nuclear antigen (PCNA) in a large group of histologically different salivary gland cancers. We analysed the expression of PCNA in 159 patients with parotid gland cancer by means of immunohistochemistry. The mean follow-up time was 56.6 months. A high expression of PCNA showed a significant correlation to the patients' pathological lymph node stage (p = 0.004). A high PCNA expression significantly indicated a poor 5-year disease-free (p = 0.046) and overall survival rate (p = 0.018). The PCNA expression was the only prognostic factor for a worse 5-year disease-free and overall survival in acinic cell carcinomas (p = 0.004, p = 0.022). The correlation between PCNA expression and survival probabilities of salivary gland cancer might make proliferation markers helpful tools in patient follow-up, prognosis and targeted therapy in salivary gland cancer in future.

Prognostic value of survivin expression in parotid gland cancer in consideration of different histological subtypes.

BACKGROUND: Cancer of the major salivary glands comprises a morphological diverse group of rare tumours of largely unknown cause. Survivin, an inhibitor of apoptosis has shown to be a significant prognostic indicator in various human cancers. The aim of this study was to assess the long-term prognostic value of survivin in a large group of histological different salivary gland cancers. METHODS: We analysed the survivin expression in 143 patients with parotid gland cancer by means of immunohistochemistry and tissue micro array. Survivin expression was categorised into a low and a high expressing group. The experimental findings were correlated with clinicopathological and survival parameters. The mean follow-up time was 54.8 months. RESULTS: A positive cytoplasmic expression of survivin was found in 61.5%, a high expression in 25.9% of all specimens. In the whole group, high cytoplasmic survivin expression significantly indicated a poor 5-year disease-free and overall survival rate (p < 0.0001, p = 0.003). This applied for all adeno-, adenoid cystic and undifferentiated carcinomas whereas in mucoepidermoid carcinomas an analogical non-significant trend could be observed. A high cytoplasmic survivin expression significantly indicated a poor survival in high grade but not in low grade tumours. A multivariate analysis revealed that high cytoplasmic survivin expression was the only significant negative prognostic indicator for a poor 5-year disease-free survival rate in all patients (p = 0.042). CONCLUSION: The correlation between cytoplasmic survivin expression and survival probabilities of salivary gland cancer might make this an effective tool in patient follow-up, prognosis and targeted therapy in future.