Environmental assessment in early process development

A short‐cut method for environmental assessment during process development is presented. The method can deal with data uncertainties in early phases, includes all relevant environmental impacts, and is simple and easy to apply. Therefore, it can be used in early phases of process development. The environmental relevance of each substance is represented by the Environmental Factors. These factors are derived from 14 impact categories, where each compound is classified using an ABC methodology. The impact categories are then grouped into six impact groups: Resources, Grey Input, Component Risk, Organisms, Air and Water/Soil. From these, input and output environmental factors are deduced. This factor is combined with mass balance data to yield a number of indices that can be used to optimize the environmental performance of a process in an integrated manner. The method is applied to three case studies: a comparison of chemical and biotechnological production of 6‐aminopenicillanic acid, a comparison of two process alternatives in the enzymatic production of α‐cyclodextrin and the development of a new process for the fermentative production of pyruvate. Copyright © 2004 Society of Chemical Industry     

Metal-organic vapor phase epitaxy for the mass production of novel semiconductor devices

We report on growth results achieved in AIXTRON multiwafer planetary reactors for the growth of phosphide-arsenide and nitride based novel semiconductor structures and devices. In case of the phosphide-arsenide based structures we focused on growth on 6-in GaAs wafers. Ga/sub 0.47/InP layers were grown with standard deviations for the Ga-concentration of 0.75% and 0.3% on wafer and wafer-to-wafer, respectively. We attribute this result to the excellent temperature homogeneity of 1/spl deg/C throughout the reactor. This factor also plays a role in the deposition of nitride-based semiconductors that was investigated for the growth of InGaN multiquantum wells for the blue (472 nm) and green (522 nm) wavelengths. Wafer-to-wafer wavelength distributions of max-min of /spl plusmn/2.1 nm (blue) and /spl plusmn/4.2 nm (green) were achieved. On wafer standard deviations of the wavelength fell in the range of 1.6-1.7 nm, respectively.     

Afferent large fiber polyneuropathy predicts the development of postherpetic neuralgia

Acute zoster infection may be followed by a chronic pain syndrome, i.e., postherpetic neuralgia (PHN). Besides older age, the intensity of pain and neuronal damage within the acutely affected body region are regarded as predictors or risk factors for PHN. As an alternative approach an underlying peripheral polyneuropathy may be considered as potential co-factor. Is a preexisting generalized impairment of certain fiber classes important in initiating chronic pain states after subsequent localized nerve lesion due to zoster infection? Neurophysiological tests of different efferent and afferent small and large fiber systems were performed prospectively at unaffected body regions in patients with acute herpes zoster. Patients that were still in pain 6 months later (PHN, n = 17) and pain free patients (non-PHN, n = 17) were compared regarding the results obtained during the acute phase. Both groups were age matched. Nociceptive C-fiber function was assessed at the forearm by quantitative measurement of the axon reflex vasodilatation and flare induced by histamine iontophoresis. Mechanosensitive A beta-fibers were tested at all extremities by quantitative vibrametry. Parasympathetic small fiber function was studied by heart rate variability tests. No clinically manifest polyneuropathy was present. However, in PHN risk patients considerably higher vibration detection thresholds in hands and feet were detected compared with non-PHN patients. Pathologic test results of vibration sense at the lower extremity predicted PHN with a sensitivity of 70%. Nociceptive C-fiber and parasympathetic fiber function demonstrated no significant differences in both groups. Acute zoster pain was slightly more intense in the PHN group. We concluded that (i) a mild generalized impairment of afferent A beta-fiber function (A beta-polyneuropathy) seems to be an important co-factor in the development of PHN and (ii) impairment of vibration sense, i.e., impairment of afferent A beta-fiber function, may be used as a predictor of PHN.     

Guest Editorial

Journal of Signal Processing Systems -     

Molecular characterization and functional analysis of murine interleukin 4 receptor allotypes

The murine interleukin 4 receptor (IL-4R) exists as a transmembrane protein transducing pleiotropic IL-4 functions, or as soluble (s)IL-4-binding molecule with potent immunoregulatory effects. In this study we identified and characterized a murine IL-4R allotype. Sequence analysis of the IL-4R cDNA of BALB/c mice revealed 18 base substitutions leading to three extracellular and five cytoplasmic amino acid changes when compared with the published IL-4R sequence of C57BL/6 mice. Analyses with allotype-specific mAbs revealed that AKR/J and SJL/J mice possess the newly identified BALB/c IL-4R allotype whereas the IL-4Rs of C3H, CBA, DBA-2, and FVB/N mice are identical to that of the C57BL/6 mouse. The extracellular Thr49 to Ile substitution abrogates one N-glycosylation site in the naturally occurring BALB/c IL-4R as well as in the experimentally point mutated C57BL/6-T49I sIL-4R, and both molecules display a nearly threefold reduction in IL-4-neutralizing activity compared to the C57BL/6 sIL-4R. In line with this, a significantly enhanced dissociation rate of IL-4 was detected for the BALB/c IL-4R allotype by surface plasmon resonance and in radioligand binding studies with IL-4R-transfected cell lines. These findings suggest that the altered ligand binding behavior of the newly described IL-4R allotype may influence the IL-4 responsiveness, thus contributing to the diverse phenotypes of inbred mouse strains in IL-4-dependent diseases.     

Mobility of modulation doped AlGaAs/low-temperature MBE-grown GaAs heterostructures

A study of the mobility of a novel modulation doped heterostructure in which the channel region is made of low-temperature molecular beam epitaxially grown GaAs (LT-GaAs) and all other layers are grown at normal temperatures is presented for the first time. The resistivity of the as-grown samples(in- situ annealed) is very high, as is that of single layers of bulk LT-GaAs. However, in the presence of light, the resistivity of the LT-GaAs modulation-doped field effect transistor (MODFET) is significantly lower, facilitating reliable Hall measurements. We speculate that the observed decrease in resistivity of the LT-GaAs MODFET is due to the formation of a two-dimensional electron gas (2DEG) at the heterointerface under illumination. A number of samples grown under different growth conditions were investigated. Mobilities for these samples were found to be in the range of 250 to 750 cm²Vs at 300K and ∼3000 to 5500 cm²Vs at 77K. A first-order computer simulation was implemented to calculate the mobility of the 2DEG using the relaxation-time approximation to solve the Boltzmann equation, taking into account different scattering mechanisms. Scattering by the arsenic clusters and by ionized impurities in the LT-GaAs MODFET channel are found to be the two dominant mechanisms limiting the mobility of the LT-GaAs MODFET samples. Experimental values are in good agreement with theoretical results.     

Morphomechanics of the humero-ulnar joint: I. Joint space width and contact areas as a function of load and flexion angle

BACKGROUND: Previous studies have shown that the trochlear notch is deeper than necessary for an exact fit with the humerus. However, humero-ulnar joint space width and contact areas have so far not been quantified for variations in the load and angle of flexion. METHODS: Six fresh cadaveric specimens were investigated at 30 degrees, 60 degrees, 90 degrees, and 120 degrees of flexion and at loads of 25 and 500 N, simulating resisted elbow extension. The joint space width and contact were determined, using polyether casting material. RESULTS: At 25 N all joints made contact in the ventral and dorsal aspects of the articular surfaces, whereas in the depth of the trochlear notch the joint space was on average between 0.3 and 2.8 mm wide, with some variation between individuals. At 500 N the joint space width was considerably reduced and the contract areas expanded towards the depth of the notch. The size of the dorsal contact areas was significantly smaller at 30 degrees and that of the ventral ones at 120 degrees, their ventro-dorsal ratio decreasing considerably from 30 degrees to 120 degrees (p < 0.01). CONCLUSION: These results indicate that the size of the contact areas depends to a slight extent on the joint position, but that at all loads and flexion angles a bicentric contact and an important central joint space width emerge because of the concave incongruity of the joint. These data may be used for numerical calculations, analysing the effects of incongruity on the joint stress and on the functional adaptation of the subarticular tissues.     

Changes in the secretion of growth hormone in severely injured persons (author's transl)

The secretion of growth hormone was studied in 25 severely injured persons during the adaptive and convalescent stage. The ages of the patients varied between 9--65 years. During the first few days after the trauma hormone concentrations rose to up to 7--15 times their normal upper limits (about 10 mU/l). In some cases the hormone levels subsequently fell to the lower limits of normal. No attempt was made to calculate average values and the reasons for the omission are stated. The results are discussed with reference to the metabolic condition of the severely injured persons.