The effect of an oxide layer on the ohmicity of contacts to amorphous silicon

Surface oxide layers on CVD films of amorphous silicon can cause the metallic contacts to the films to be non-ohmic. Dipping an amorphous silicon sample in a solution of hydrofluoric acid prior to electrode deposition removes the oxide layer and permits the formation of ohmic contacts.     

Influence of serum, estrogen, and gonadotropins upon growth and progesterone secretion by cultures of granulosa cells from small porcine follicles

Granulosa cells from small (less than 2mm) antral porcine follicles were grown in culture to study the effects of various hormones on growth, morphology and progesterone secretion. Culture medium 199D + 4% serum was found to be most suitable since it maintained a fairly constant cell population. Estradiol (1mug/ml) and human FSH stimulated cell growth. LH and FSH stimulated progesterone secretion and induced morphological changes associated with luteinization. Estradiol (0.1 mug/ml) inhibited progesterone secretion by granulosa cells.     

Synergistic science

Should computational materials science be recognized as a field with a role in the community comparable to computational physics or chemistry? With the emergence of multiscale modelling, the answer is a resounding 'yes'.     

Ergonomics and sustainability: towards an embrace of complexity and emergence

Technology offers a promising route to a sustainable future, and ergonomics can serve a vital role. The argument of this article is that the lasting success of sustainability initiatives in ergonomics hinges on an examination of ergonomics’ own epistemology and ethics. The epistemology of ergonomics is fundamentally empiricist and positivist. This places practical constraints on its ability to address important issues such as sustainability, emergence and complexity. The implicit ethical position of ergonomics is one of neutrality, and its positivist epistemology generally puts value-laden questions outside the parameters of what it sees as scientific practice. We argue, by contrast, that a discipline that deals with both technology and human beings cannot avoid engaging with questions of complexity and emergence and seeking innovative ways of addressing these issues.

Practitioner Summary: Ergonomics has largely modelled its research on a reductive science, studying parts and problems to fix. In sustainability efforts, this can lead to mere local adaptations with a negative effect on global sustainability. Ergonomics must consider quality of life globally, appreciating complexity and emergent effects of local relationships.     

Relationship between lateral subluxation and widening of medial joint space in Legg-Calvé-Perthes disease

Fifty-five patients (61 affected hips and 49 unaffected hips) with Perthes disease were reviewed to evaluate the relationship between widening of medial joint space and lateral subluxation of the femoral head in radiographs. The components of the medial joint space were evaluated by using T1, T2, proton, and Gd-enhanced T1WI magnetic resonance images (MRI). The widened medial joint space in radiographs was filled with overgrown cartilage at the initial stage (27 hips) in MRI, with both overgrown cartilage and widened true medial joint space at the fragmentation stage (23 hips) and widened true medial joint space at the healing stage (11 hips). Between affected hips and unaffected hips, the mean difference of medial joint space in radiographs between hips at the initial stage and at the fragmentation stage was 2 and 4.5 mm, respectively; the mean difference in percentage of lack of coverage of the femoral head between hips at the initial stage and at the fragmentation stage was 3 and 15%, respectively. During the healing stage, widening of the medial joint space decreased or normalized because of ossification of overgrown cartilage despite the existence of lateral subluxation because of coxa magna. We concluded that widening of the medial joint space may be used as an index of lateral subluxation at only the fragmentation stage in Perthes disease.     

Changes in RBE of 14-MeV (d + T) neutrons for V79 cells irradiated in air and in a phantom: is RBE enhanced near the surface?

PURPOSE: The relative biological effectiveness (RBE) for inactivation of V79 cells was determined as function of dose at the Heidelberg 14-MeV (d + T) neutron therapy facility after irradiation with single doses in air and at different depths in a therapy phantom. Furthermore, to assess the reproducibility of RBE determinations in different experiments we examined the relationship between the interexperimental variation in radiosensitivity towards neutrons with that towards low LET 60Co photons. METHODS: Clonogenic survival of V79 cells was determined using the colony formation assay. The cells were irradiated in suspension in small volumes (1.2 ml) free in air or at defined positions in the perspex phantom. Neutron doses were in the range, Dt = 0.5-4 Gy. 60Co photons were used as reference radiation. RESULTS: The radiosensitivity towards neutrons varied considerably less between individual experiments than that towards photons and also less than RBE. However, the mean sensitivity of different series was relatively constant. RBE increased with decreasing dose per fraction from RBE = 2.3 at 4 Gy to RBE = 3.1 at 0.5 Gy. No significant difference in RBE could be detected between irradiation at 1.6 cm and 9.4 cm depth in the phantom. However, an approximately 20% higher RBE was found for irradiation free in air compared with inside the phantom. Combining the two effects, irradiation with 0.5 Gy free in air yielded an approximately 40% higher RBE than a dose of 2 Gy inside the phantom. CONCLUSION: The measured values of RBE as function of dose per fraction within the phantom is consistent with the energy of the neutron beam. The increased RBE free in air, however, is greater than expected from microdosimetric parameters of the beam and may be due to slow recoil protons produced by interaction of multiply scattered neutrons or to an increased contribution of alpha particles from C(n, alpha) reactions near the surface. An enhanced RBE in subcutaneous layers of skin combined with an increase in RBE at low doses per fraction outside the target volume could potentially have significant consequences for normal tissue reactions in radiotherapy patients treated with fast neutrons.     

Persistent GAD 65 antibodies in longstanding IDDM are not associated with residual beta-cell function, neuropathy or HLA-DR status

Persistent humoral autoimmunity to the enzyme glutamic acid decarboxylase (GAD) has been described in a substantial proportion of patients with insulin-dependent diabetes mellitus (IDDM) of long duration. The source of the stimulus for this autoimmune reactivity is still unknown. Because the GAD 65 isoform is mainly expressed in pancreatic beta-cells and in the nervous system we investigated in the present study of the largest number of well characterized patients with longstanding IDDM (n = 105; median duration: 21 years; range: 10-46 years) the presence of autoantibodies to GAD 65 and their relationship to a residual C-peptide response or peripheral and autonomic neuropathy. Additionally we studied the HLA-DR status relative to GAD 65 antibodies in 86 out of the 105 individuals. One hundred healthy control subjects and 100 recent onset IDDM patients were also studied for GAD 65 antibodies. GAD 65 antibodies were detected in a radioligand-binding-assay with recombinant human GAD 65 and were present in 32% of the long-term diabetic patients, 82% of the recent onset IDDM patients and in 3% of the healthy control subjects. A preserved C-peptide response to i.v. glucagon (Hendriksen criteria) was observed in 23% of the long-term IDDM patients. Autonomic neuropathy and peripheral neuropathy was identified using criteria based on both symptoms and formal testing giving a frequency of 67% vs 79%. The HLA specific DR 4/X was observed in 47% and HLA-DR 3/X in 22% of the long-term IDDM patients. Patients who were heterozygous for DR3/DR4 were found in 23% of the cases. GAD 65 antibodies were significantly less frequent in the long-term IDDM patients compared to recent onset IDDM (p < 0.001), and diabetes duration showed a significant negative correlation with GAD 65 antibody index levels (r = 0.22, p < 0.01). Interestingly, GAD 65 antibodies were not significantly correlated either with residual beta-cell function or neuropathy and no particular HLA-DR status was associated with persistent GAD 65 antibodies. In conclusion neither residual beta-cell function nor diabetic neuropathy or a certain HLA-DR specificity are exclusively associated with persistent autoimmunity directed to GAD 65 in longstanding IDDM. The stimulus for the persistent humoral immune response and its significance for the disease process and its complications remain to be established.