Ion yields and erosion rates for Si1−xGex(0x1) ultralow energy O2+ secondary ion mass spectrometry in the energy range of 0.25–1 keV

We report the SIMS parameters required for the quantitative analysis of Si1−xGex across the range of 0 ≤ x ≤ 1 when using low energy O2+ primary ions at normal incidence. These include the silicon and germanium secondary ion yield [i.e., the measured ion signal (ions/s)] and erosion rate [i.e., the speed at which the material sputters (nm/min)] as a function of x. We show that the ratio Rx of erosion rates, Si1−xGex/Si, at a given x is almost independent of beam energy, implying that the properties of the altered layer are dominated by the interaction of oxygen with silicon. Rx shows an exponential dependence on x. Unsurprisingly, the silicon and germanium secondary ion yields are found to depart somewhat from proportionality to (1−x) and x, respectively, although an approximate linear relationship could be used for quantification across around 30% of the range of x (i.e., a reference material containing Ge fraction x would give reasonably accurate quantification across the range of ±0.15x). Direct comparison of the useful (ion) yields [i.e., the ratio of ion yield to the total number of atoms sputtered for a particular species (ions/atom)] and the sputter yields [i.e., the total number of atoms sputtered per incident primary ion (atoms/ions)] reveals a moderate matrix effect where the former decrease monotonically with increasing x except at the lowest beam energy investigated (250 eV). Here, the useful yield of Ge is found to be invariant with x. At 250 eV, the germanium ion and sputter yields are proportional to x for all x

Characterization of the Noise in Secondary Ion Mass Spectrometry Depth Profiles

The noise in the depth profiles of secondary ion mass spectrometry (SIMS) is studied using different samples under various experimental conditions. Despite the noise contributions from various parts of the dynamic SIMS process, its overall character agrees very well with the Poissonian rather than the Gaussian distribution in all circumstances. The Poissonian relation between the measured mean-square error (MSE) and mean can be used to describe our data in the range of four orders. The departure from this relation at high counts is analyzed and found to be due to the saturation of the channeltron used. Once saturated, the detector was found to exhibit hysteresis between rising and falling input flux and output counts.Comment: 14 pages, 4 postscript figures, to appear on J. Appl. Phy

Dopant Spatial Distributions: Sample Independent Response Function And Maximum Entropy Reconstruction

We demonstrate the use of maximum entropy based deconvolution to reconstruct boron spatial distribution from the secondary ion mass spectrometry (SIMS) depth profiles on a system of variously spaced boron $\delta$-layers grown in silicon. Sample independent response functions are obtained using a new method which reduces the danger of incorporating real sample behaviour in the response. Although the original profiles of different primary ion energies appear quite differently, the reconstructed distributions agree well with each other. The depth resolution in the reconstructed data is increased significantly and segregation of boron at the near surface side of the $\delta$-layers is clearly shown.Comment: 5 two-columne pages, 3 postscript figures, to appear in Phys. Rev. B1

Toxicity in Beef Cattle Grazing \u3cem\u3eLeucaena leucocephala\u3c/em\u3e in Queensland, Australia

Improved pastures based on the leguminous shrub Leucaena leucocephala (leucaena) are the most productive, profitable and sustainable for beef cattle production in northern Australia. Leucaena forage contains the toxic, non-protein amino acid mimosine, which is rapidly converted to 3-hydroxy-4(1H)-pyridone (DHP) upon ingestion by grazing cattle. This is a potent goitrogen and appetite suppressant. Animals suffering severe DHP toxicity exhibit distinctive symptoms (e.g. hair loss, excessive salivation, goitre and weight loss), while subclinical DHP toxicity can suppress live weight gain by 30-50% without producing any obvious symptoms. Prior to the discovery and introduction of the DHP-degrading rumen bacteria Synergistes jonesii into Australia in 1982, DHP toxicity severely limited animal performance from leucaena pastures and was a major impediment to adoption. Initial rumen inoculation of cattle in Australia with S. jonesii successfully protected them against DHP toxicity and the bacterium appeared to be easily and rapidly transmitted between grazing animals. Consequently many scientists and graziers believed that a single inoculation of a herd with S. jonesii, combined with simple ongoing herd management, was sufficient to overcome the problem of DHP toxicity. However, during the 2003 drought there were several reports of severe leucaena toxicity (including animal deaths) in cattle grazing leucaena in Queensland. Toxicity was evident even in herds that had followed recommended control measures. Preliminary results are presented of a study, designed to ascertain the prevalence and possible causes of leucaena toxicity in Queensland cattle herds. Meat and Livestock Australia Limited funded this research (NBP.340)

Threat of Sexual Disqualification: The Consequences of Erectile Dysfunction and Other Sexual Changes for Gay and Bisexual Men With Prostate Cancer.

Gay and bisexual (GB) men with prostate cancer (PCa) have been described as an "invisible diversity" in PCa research due to their lack of visibility, and absence of identification of their needs. This study examined the meaning and consequences of erectile dysfunction (ED) and other sexual changes in 124 GB men with PCa and 21 male partners, through an on-line survey. A sub-sample of 46 men with PCa and seven partners also took part in a one-to-one interview. ED was reported by 72 % of survey respondents, associated with reports of emotional distress, negative impact on gay identities, and feelings of sexual disqualification. Other sexual concerns included loss of libido, climacturia, loss of sensitivity or pain during anal sex, non-ejaculatory orgasms, and reduced penis size. Many of these changes have particular significance in the context of gay sex and gay identities, and can result in feelings of exclusion from a sexual community central to GB men's lives. However, a number of men were reconciled to sexual changes, did not experience a challenge to identity, and engaged in sexual re-negotiation. The nature of GB relationships, wherein many men are single, engage in casual sex, or have concurrent partners, influenced experiences of distress, identity, and renegotiation. It is concluded that researchers and clinicians need to be aware of the meaning and consequences of sexual changes for GB men when designing studies to examine the impact of PCa on men's sexuality, advising GB men of the sexual consequences of PCa, and providing information and support to ameliorate sexual changes

The Depth Resolution of Secondary Ion Mass Spectrometers: A Critical Evaluation

The ability of five Secondary Ion Mass Spectrometry (SIMS) instruments to resolve thin layer and modulated dopant structures by depth profiling has been assessed. Three magnetic sector instruments (two Cameca IMS 3f\u27s and one 4f), which use optical gating and a high extraction field, were used, together with two different quadrupole based instruments (EVA 2000 and Atomika) , which use electronic gating and a low extraction field. The test structure, a thirty-one peak boron-in-silicon modulating dopant structure, was grown by Molecular Beam Epitaxy (MBE). In all the depth profiles the near surface peaks appeared narrow and asymmetric, being broadened only by fundamental processes (e.g., atomic mixing and recoil implantation). As the profiles proceeded, however, further broadening was observed. This phenomena varied markedly both from one instrument to another and from one experiment to another on the same instrument. In some cases the loss of depth resolution with depth was manifested by broadening mainly in the leading edge, in others the trailing edge, of successive boron peaks. The \u27order of merit\u27 of the instruments thus depended on the parameter used to define depth resolution. The loss of peak (depth) resolution with depth was due to variations in primary ion beam density across the gated area of the crater, which led to uneven etching. The changes in peak shape with depth can be explained by a numerical model of the etching process. These observations dictate that the depth resolution of a SIMS instrument should not be measured in terms of a single interface width, such as the leading or trailing edge

A prospective study of endogenous serum hormone concentrations and breast cancer risk in premenopausal women on the island of Guernsey.

The associations between serum concentrations of oestradiol, progesterone, testosterone and sex hormone-binding globulin (SHBG) and risk of breast cancer in premenopausal women were investigated in a prospective study of breast cancer on the island of Guernsey. Sixty-two women diagnosed with breast cancer an average of 8 years subsequent to blood collection were matched for day of menstrual cycle, age and year of blood collection with 182 control subjects. Cases had a 12% higher mean oestradiol concentration over the whole menstrual cycle (P = 0.17) with a large difference at mid-cycle (75% higher, P = 0.04). Differences between cases and control subjects in progesterone (luteal phase), testosterone and SHBG were small and not statistically significant: luteal phase progesterone 9% lower in cases, P = 0.64; testosterone 4% higher, P = 0.57; SHBG 8% higher, P = 0.24. The small difference in oestradiol concentration could be aetiologically important, but larger prospective studies are needed

Health-Related Quality of Life, Psychological Distress, and Sexual Changes Following Prostate Cancer: A Comparison of Gay and Bisexual Men with Heterosexual Men.

INTRODUCTION: Decrements in health-related quality of life (HRQOL) and sexual difficulties are a recognized consequence of prostate cancer (PCa) treatment. However little is known about the experience of gay and bisexual (GB) men. AIM: HRQOL and psychosexual predictors of HRQOL were examined in GB and heterosexual men with PCa to inform targeted health information and support. METHOD: One hundred twenty-four GB and 225 heterosexual men with PCa completed a range of validated psychosexual instruments. MAIN OUTCOME MEASURE: Functional Assessment of Cancer Therapy-Prostate (FACT-P) was used to measure HRQOL, with validated psychosexual measures, and demographic and treatment variables used as predictors. RESULTS: GB men were significantly younger (64.25 years) than heterosexual men (71.54 years), less likely to be in an ongoing relationship, and more likely to have casual sexual partners. Compared with age-matched population norms, participants in both groups reported significantly lower sexual functioning and HRQOL, increased psychological distress, disruptions to dyadic sexual communication, and lower masculine self-esteem, sexual confidence, and sexual intimacy. In comparison with heterosexual men, GB men reported significantly lower HRQOL (P = .046), masculine self-esteem (P < .001), and satisfaction with treatment (P = .013); higher psychological distress (P = .005), cancer related distress (P < .001) and ejaculatory concern (P < .001); and higher sexual functioning (P < .001) and sexual confidence (P = .001). In regression analysis, psychological distress, cancer-related distress, masculine self-esteem, and satisfaction with treatment were predictors of HRQOL for GB men (R2Adj = .804); psychological distress and sexual confidence were predictors for heterosexual men (R2Adj = .690). CONCLUSION: These findings confirm differences between GB and heterosexual men in the impact of PCa on HRQOL across a range of domains, suggesting there is a need for GB targeted PCa information and support, to address the concerns of this "hidden population" in PCa care

The final two redshifts for radio sources from the equatorial BRL sample

Best, Rottgering and Lehnert (1999, 2000a) defined a new sample of powerful radio sources from the Molonglo Reference Catalogue, for which redshifts were compiled or measured for 177 of the 178 objects. For the final object, MRC1059-010 (3C249), the host galaxy is here identified using near-infrared imaging, and the redshift is determined from VLT spectroscopy. For one other object in the sample, MRC0320+053 (4C05.14), the literature redshift has been questioned: new spectroscopic observations of this object are presented, deriving a corrected redshift. With these two results, the spectroscopic completeness of this sample is now 100%. New redshifts are also presented for PKS0742+10 from the Wall & Peacock 2.7 GHz catalogue, and PKS1336+003 from the Parkes Selected Regions. PKS0742+10 shows a strong neutral hydrogen absorption feature in its Lyman-alpha emission profile.Comment: 4 pages. LaTeX. Accepted for publication in MNRA