Apparatus for measurement of thermoelectric properties of a single leg under large temperature differences

Thermoelectric (TE) devices operate under large temperature differences, but material property measurements are typically accomplished under small temperature differences. Because of the issues associated with forming proper contact between the test sample and the electrodes and the control of heat flux, there are very few reports on large temperature difference measurements. Therefore, practically relevant performance parameters of a device, namely, power output and efficiency, are estimated by temperature averaging of material properties, whose accuracy is rarely validated by experimental investigations. To overcome these issues, we report an apparatus that has been designed and assembled to measure the TE properties-Seebeck coefficient, electrical conductivity, thermal conductivity, and power output and efficiency of a single thermoelectric material sample over large temperature gradients. The sample holder-a unique feature of this design-lowers the contact resistance between the sample and the electrodes, allowing for more accurate estimates of the sample's properties. Measurements were performed under constant temperature differences ranging from 50 to 300 K with the hot side reaching 673 K on a metallized Mg₂Si_0.3Sn_0.7 leg synthesized in the laboratory. To simulate practical operating conditions of a continuously loaded generator, continuous current flow measurements were also performed under large temperature differences. The temperature-averaged TE properties from standard low temperature difference measurements and the experimental TE properties agree with each other, indicating that the designed setup is reliable for measuring various thermoelectric generator properties of single TE legs when subjected to temperature gradients between 50 and 300 K.

Investigating charge-up and fragmentation dynamics of oxygen molecules after interaction with strong X-ray free-electron laser pulses

The X-ray-induced charge-up and fragmentation process of a small molecule is examined in great detail by measuring the molecular-frame photoelectron interference pattern in conjunction with other observables in coincidence.

Nuclear osteopontin-c is a prognostic breast cancer marker

BACKGROUND

Although Osteopontin has been known as a marker for cancer progression, the elevated production of this cytokine is not specific for cancer. We have identified the splice variant Osteopontin-c as being absent from healthy tissue but associated with about 75% of breast cancer cases. However, in previous studies of Osteopontin-c, follow-up information was not available.

METHODS

Here we have analysed 671 patients, comprising a cohort of 291 paraffin blocks plus a population-based case-control study of 380 arrayed breast tumor tissues.

RESULTS

We find that high staining intensity of nuclear Osteopontin-c is strongly associated with mortality in patients with early breast cancer. Cytosolic staining for exon 4, reflective of Osteopontin-a and -b also predicts poor outcome. By contrast, total Osteopontin does not correlate with prognosis. These diverse assessments of Osteopontin also do not correlate with each other, suggesting distinct expression patterns for the variant forms. Consistent with its role in tumor progression, not tumor initiation, Osteopontin-c is not correlated with proliferation markers (Ki-67, cyclin A, cyclin B, cyclin E and cyclin D), neither is it correlated with ER, PR or HER2.

CONCLUSIONS

The addition of Osteopontin-c immunohistochemistry to standard pathology work-ups may have prognostic benefit in early breast cancer diagnosis.

Improvement of spatial resolution for local Seebeck coefficient measurements by deconvolution algorithm

A potential Seebeck microprobe apparatus is described such that a profile of Seebeck coefficients can be detected on a material sample surface for thermopower investigations. Due to its spatially resolved limit on detecting small inhomogeneities of dopants or composition changes, we here propose a constructive combination of numerical modeling and practical measurement to improve the spatial resolution by deconvolution algorithm. The relevant transfer function, obtained from numerical calculations, was successfully applied on real measurement data. Besides, an improvement in detecting the 1.5 microm inhomogeneity has been achieved by applying one transfer function of the known tip setup on a set of Seebeck line scan signals, obtained with 6 microm tip-sample contact length, 3 micros signal capture time after contact, and 0.75 microm scan period. The result showed that a system theoretical approach in terms of deconvolution algorithm could theoretically enhance the spatial resolution anyway, but is practically limited by the systemic preconditions (tip size, signal capture time, and scan period) and the signal to noise ratio of the captured thermovoltages. Therefore, we provide a clear understanding of systemic preconditions and their impacts on the detection of small inhomogeneities and thus the performance in the thermopower analysis.

Photodynamic therapy combined with a cysteine proteinase inhibitor synergistically decrease VEGF production and promote tumour necrosis in a rat mammary carcinoma

OBJECTIVES

Photodynamic therapy (PDT) and inhibition of cathepsin B proteases by cystatin (cysteine proteinase inhibitor, CPI) are potential new tumour treatment modalities. We have investigated the efficacy of PDT and CPI alone and in combination on a solid mammary carcinoma transplanted into Wistar rats.

MATERIALS AND METHODS

Intraperitoneally injected single doses of chlorine e6 or HpD as photosensitizers were excited at 630 nm (90 J/cm(2)). CPI (500 micro g per animal) was injected around the tumour daily during the 8-day treatment. Inoculation of tumour was either on day 1 of the protocol, or 8 days before. On day 8, tumour size was measured, tumour necrosis and vascularization were determined based on haematoxylin and eosin (H&E)-stained sections and serum vascular endothelial growth factor (VEGF) levels measured using an enzyme-linked immunosorbent assay kit.

RESULTS

No differences (two-way anova) were found for treatments started with various time lags. At doses where CPI or PDT alone had no or negligible effect, their combination caused a marked (P < 0.001) decrease in serum VEGF, paralleled by a significant decrease in tumour size and number of capillary vessels, and a significant increase in necrosis (up to 80% of the tumour tissue).

CONCLUSIONS

The combination of PDT and CPI could be a useful approach in tumour therapy as the two agents appear to be synergistic and probably decrease VEGF production by the tumour tissue.

[The significance of TU M2-PK tumor marker for lung cancer diagnostics]

The purpose of the study was to investigate significance of the tumor marker pyruvate kinase Tumor M2 (Tu M2-PK), in diagnostics, monitoring of treatment, and evaluation of its effectiveness in patients with lung cancer (LC). This is an isoform of the glycosile enzyme pyruvate kinase, existing as an active dimer and less active tetramer. The expression of the less active form is typical of tumor cells; its blood level can be measured. The subjects of the study were 140 patients with LC of various histologic types. Serum levels of certain tumor markers (Cyfra 21-1, NSE, SCC, and Tu M2-PK) were measured; Tu M2-PK level was determined by ELISA test from ScheBoTech, a two-stage sandwich immunoassay using one type of antibodies. The marker concentration was also determined in 195 healthy volunteers (control group.) The maximum concentration of Tu M2-PK was 12.9 U/ml, determined with 95% specificity. 78% of the patients with small-cell carcinoma, 73% of patients with adenocarcinoma, and 81% of patients with non-small cell lung carcinoma displayed increase of Tu M2-PK serum concentration; this concentration was within normal limits in patients with nonmalignant diseases (e.g. bronchitis or tuberculosis). Thus, patients with lung carcinoma display a pathologic increase of Tu M2-P level. Measurement of Tu M2-P may be useful in patients with suspected LC; this marker may be of greater diagnostic significance than SCC or NSE.

The combined treatment of transplantable solid mammary carcinoma in Wistar rats by use of photodynamic therapy and cysteine proteinase inhibitor

Numerous studies have shown that lysosomal proteinases play an important role in carcinogenesis. The enzymatic activity of tumor-associated proteases is counter-balanced by specific inhibitors. Photodynamic therapy (PDT) is a technique which involves photoexcitation of sensitizing drugs retained in neoplastic tissue that is subsequently destroyed. Intraperitoneal injections of hematoporphyrin derivative (HpD) were given at a dose of 20 mg/kg in rats transplanted with mammary carcinoma. A halogen lamp was used 24 hours later at 630 +/- 20 nm and total dose--200 J/sq.cm. Cysteine proteinase inhibitor (CPI) was dissolved in saline and injected subcutaneously in doses of 50 mg and 200 mg per animal. The effectiveness of the treatment was evaluated with regard to survival time and tumor response and to depth of necrosis. In several cases tumors completely disappeared following HpD-PDT + CPI. The number of complete tumor responses was higher when PDT + 200 mg of CPI was used, i.e. 6 out of 10 rats. Promising results have also been obtained with regard to survival time of treated animals and to induction of tumor necrosis. We may presume that a combination of PDT and proteinase inhibitors could be a useful tool in further anticancer studies and, hopefully, in anticancer therapy.