A novel method for determining calibration and behavior of PVDF ultrasonic hydrophone probes in the frequency range up to 100 MHz

A new calibration technique for PVDF ultrasonic hydrophone probes is described. Current implementation of the technique allows determination of hydrophone frequency response between 2 and 100 MHz and is based on the comparison of theoretically predicted and experimentally determined pressure-time waveforms produced by a focused, circular source. The simulation model was derived from the time domain algorithm that solves the non linear KZK (Khokhlov-Zabolotskaya-Kuznetsov) equation describing acoustic wave propagation. The calibration technique data were experimentally verified using independent calibration procedures in the frequency range from 2 to 40 MHz using a combined time delay spectrometry and reciprocity approach or calibration data provided by the National Physical Laboratory (NPL), UK. The results of verification indicated good agreement between the results obtained using KZK and the above-mentioned independent calibration techniques from 2 to 40 MHz, with the maximum discrepancy of 18% at 30 MHz. The frequency responses obtained using different hydrophone designs, including several membrane and needle probes, are presented, and it is shown that the technique developed provides a desirable tool for independent verification of primary calibration techniques such as those based on optical interferometry. Fundamental limitations of the presented calibration method are also examined.     

Antennal sensilla of two parasitoid wasps: a comparative scanning electron microscopy study

Two closely related parasitoid wasp species, Cotesia glomerata (L.) and Cotesia rubecula (Marshall) (Hymenoptera:Braconidae), are different in their associative learning of plant odors. To provide a solid basis for our research on the mechanisms that underlie this difference, we described the morphology of the antennal sensilla of these two species using scanning electron microscopy complemented with transmission electron microscopy. Female and male antennae of both species have the same six types of sensilla. We classified these sensilla as sensilla trichodea without pores, sensilla trichodea with a tip pore, sensilla trichodea with wall pores, sensilla coeloconica type I, sensilla coeloconica type II, and sensilla placodea. We conclude that the morphology, numbers, and distribution of the sensory receptors are highly similar in these two closely related wasp species. Differences between species and sexes occurred only in sensilla placodea numbers. C. rubecula has more sensilla placodea than C. glomerata and males of both species have a larger number and a higher density of sensilla placodea compared to females of the same species.     

Achievement in Math and Science: Do Mothers' Beliefs Matter 12 Years Later?

Past research has indicated an association between parents' beliefs and adolescent children's self-perceptions of ability and has shown the importance of accounting for parents' gender-stereotyped beliefs when examining boys' and girls' self-perceptions of math-science ability. The current study extends these findings by examining the longitudinal relations between mothers' earlier gender stereotypes and perceptions and adolescents' later math-science achievement beliefs and career choices. As predicted, mothers' earlier perceptions of their adolescents' abilities were related to adolescents' math-science self-efficacy 2 years after high school, with adolescents' self-perceptions of math ability during 10th grade mediating the relation with mothers' perceptions. Moreover, mothers' earlier predictions of their children's abilities to succeed in math careers were significantly related to later career choices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term disease-free survival after isolated peritoneal metastasis from colonic cancer

We present the case of a 29-year-old female patient with an isolated peritoneal metastatic mass in the Douglas pouch, following ileocecal resection for a Dukes C2 colon cancer of the caecum. As initial treatment, four courses of continuous infusion with epiadriamycin were administered. The effect on the tumour size was marginal. Palliative radiotherapy (33 Gy) resulted in a reduction of the tumour size and subsequently a wide posterior exenteration could be performed. Five years after the initial diagnosis the patient is still in good health with no evidence of tumour recurrence. We sincerely believe that a maximum effort aiming for cure is warranted in selected patients with localized residual or metastatic peritoneal colon cancer, even if the initial prospects seem less favourable.     

Measurement of interleukin-6 production by monocytes for in vitro safety testing of hemoglobin solutions

Induction of interleukin-6 (IL-6) production by isolated human mononuclear blood cells was taken as in vitro model for the induction of inflammatory reactions. The model was very sensitive to bacterial endotoxin (detection limit < 10pg/ml). Hemoglobin (Hb) solutions, prepared under non-sterile conditions also induced IL-6 production, which correlated with a positive reaction in the Limulus assay. Purification of the Hb solutions with a detergent prevented IL-6 production, showing that pure Hb itself does not activate the monocytes. We conclude that this assay is a useful and sensitive test of contamination with components that can induce inflammatory reactions, especially microbial products.     

Role of nucleotide excision repair in processing of O4-alkylthymines in human cells

O4-Alkylthymines have been implicated as potential carcinogenic DNA lesions. We have studied the effects of O4-methylthymine, O4-ethylthymine, and O4-n-propylthymine in a model system in which a single lesion was located at a defined position on a SV40-based shuttle vector and have found large differences in the effects of these lesions in repair-proficient and nucleotide excision repair-deficient cells. In repair-competent human HeLa cells, normal fibroblasts, and XP-A (2OS) revertant cells, all 3 residues were highly mutagenic; a mutation frequency of approximately 20% was found for both O4-methylthymine and O4-ethylthymine, whereas that of O4-n-propylthymine was approximately 12%. These frequencies were independent of the activity of the O6-alkylguanine DNA alkyltransferase. All three O4-alkylthymines induced T-->C transitions exclusively. In nucleotide excision repair-deficient XP-A cells, however, these lesions were not mutagenic but strongly inhibited plasmid replication (> 90%). These results indicate that O4-alkylthymines are efficiently recognized by the nucleotide excision repair system and cause a complete cessation of plasmid replication if this system is deficient. Nevertheless, proficiency in the nucleotide excision repair pathway correlates with a high frequency of mutation induction by these lesions.     

Safety evaluation of a polymerized hemoglobin solution in a murine infection model

Several investigators have observed that free hemoglobin may increase the mortality rate in experimental Escherichia coli peritonitis in animals. This effect is probably mediated by the heme moiety of hemoglobin, but the mechanism remains controversial. Free hemoglobin might impair neutrophil function, and it might serve as a source of iron, which is necessary for bacterial replication. Several modified hemoglobin solutions, developed as blood substitutes, are currently being tested in clinical studies, but concern exists that these solutions may have the potential to exacerbate a bacterial infection. At the Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, a blood substitute based on modified hemoglobin (PolyHbXl) has been developed that has improved oxygen affinity and prolonged vascular retention. In the present study the potential risk of this solution on the promotion of infections has been evaluated. PolyHbXl was intravenously injected into mice in a clinically relevant dose of 1.5 gm/kg body weight 1 hour before intravenous administration of a sublethal number of Listeria monocytogenes, Salmonella typhimurium, E. coli, or Candida albicans organisms. PolyHbXl did not promote the proliferation of any of these microorganisms in the liver and spleen, nor did it lead to an increased mortality rate in the mice. Also, the in vitro proliferation of L. monocytogenes, S. typhimurium, and E. coli was not increased by PolyHbXl. In conclusion, PolyHbXl does not affect the course of infection with various microorganisms in mice, and no indication was found that this new blood substitute compromises the host defense against infections.     

Eye-preserving treatment of uveal melanoma. Leidse Oogmelanoom Groep]

Over 100 new cases of uveal melanoma are diagnosed annually in the Netherlands. In the absence of metastases, eye-preserving treatment is possible in principle. Since 1984, Dutch patients are referred for eye-preserving treatment to Leiden University Hospital which consequently has gained great experience. Brachytherapy (with Ruthenium-106 applicators) is only suitable for uveal melanomas with a diameter < or = 15 mm and a prominence (thickness perpendicular to the sclera) < or = 5 mm; after 10 years, the eye was preserved in 80% of the patients; 75% retained a visual acuity > or = 0.25. Proton irradiation is being applied for large, strongly prominent melanomas in patients for whom enucleation is not acceptable, for instance with a melanoma in the only eye still functioning. The eyes could be preserved in 83.3% over a period of 5 years. Transpupillary thermotherapy combined with episcleral Ruthenium-106 application is called sandwich therapy; in a study involving 50 patients, 49 melanomas (98%) began to regress within 4 weeks and after a follow-up period of 12 months all tumours with a prominence < 5 mm had regressed completely.