Slip Control System for a Deep-Sea Mining Machine

Tracked vehicles capable of locomotion in the deep sea are used for manganese nodule mining. This requires specific technical solutions in various respects. Locomotion in the soft sea bed is one of them. For the Crawler to safely maneuver, an automatic drive mode with slip control of the driving tracks is essential. Based on experimental studies at IKS, University of Siegen, slip control for the NIOT-IKS mining machine has been developed and implemented. The experimental setup for the development of the slip control along with the logic of the automatic driving mode is described. The system is critically discussed and the test results and future work are briefly outlined. Note to Practitioners-The work is carried out as part of the polymetallic nodule mining program of the Government of India. The technique of slip control is a specific requirement for a tracked vehicle used in the deep sea. Slip is common in many vehicles-tracked and otherwise. Examples are steam engines in the early days and ordinary cars while negotiating slush or snow/ice and dozers working in soft soil. While these are manually controlled by drivers who have firsthand knowledge of the environmental conditions, in the case of a mining machine in deep sea, it has to be completely automatic and, hence, is challenging. The knowledge generated in this work could be effectively used by practitioners in other related areas of automobile engineering for updating their expertise. Also, similar techniques may be used for maneuvering vehicles sent to other planets     

Effect of short-term storage on phenolic content,o-diphenolase and peroxidase activities of cut yam tubers (Dioscorea sp)

The effect of short-term storage on the protein, phosphorus and phenolic content as well as peroxidase and o-diphenolase activities of cut, harvested Jamaican yam (Dioscorea sp) tubers (D rotundata. D alata and D cayenensis) was studied. There was an initial increase in the total phenolic content up to the third week of storage followed by a gradual decrease to the sixth week. Phenolic content was found to be highest in D cayenensis followed by D rotundata and D alata. The activities of peroxidase (EC 1. 11. 1. 7) and o-diphenolase (EC 1. 10.3.1) increased steadily up to the third week of storage and thereafter decreased to the fifth week. The intensity and rapidity of browning in tubers when cut, correlated very closely with the tuber o-diphenolase and phenolic content levels while the onset of rotting correlated with the peroxidase activity levels in the species studied.     

Two geometrical isomers of linoleic acid: Improved total syntheses

The total syntheses of 9(Z),12(E)- and 9(E),12(Z)-octadecadienoic acids have been carried out. A useful intermediate in both syntheses, 8-bromo-octanoic acid, recently has become available from commercial sources. This compound has been used to expedite the preparation of these isomers. The remaining carbon atoms were derived from propargyl alcohol along with either 1-heptyne or acetylene and 1-bromopentane. Because the overall yield for each sequence was roughly 15% and there were no extraordinary reaction conditions in any of the synthetic steps, the compounds could be prepared readily in multiple gram quantities. The syntheses of the two compounds were supported by data from a variety of spectroscopic techniques.     

Expression of INK4 inhibitors of cyclin D-dependent kinases during mouse brain development

In situ hybridization of mouse embryo sections demonstrated expression of mRNAs encoding two polypeptide inhibitors (p18INK4c and p19INK4d) of cyclin D-dependent kinase (CDK) 4 and CDK6 in the central nervous system. No expression of two other INK4 members, p16INK4a and p15INK4b, was observed. The p19INK4d and p18INK4c proteins formed complexes with either CDK4 or CDK6 in a temporal pattern consistent with the results of in situ hybridization. Expression of INK4c was observed at embryonic day 13.5 in neuroepithelial zones of the developing brain, being restricted to dividing neuroblasts but absent from differentiating postmitotic neurons. In the neocortex, p18INK4c was expressed precisely at those developmental stages when neuroblasts switch from a symmetric to an asymmetric pattern of cell division with concomitant increases in their G1 interval. INK4d RNA was detected from embryonic day 11.5 onward, at higher levels than INK4c and with a distinctly different spatial and temporal pattern. Marked INK4d expression was seen in dorsal root ganglia, spinal cord, and focally throughout the brain, but primarily in postmitotic neurons. Neural expression of INK4d continued postnatally into adulthood in postmitotic cells of the dentate gyrus, the pyramidal layer of the hippocampus, and in discrete regions of the cerebral cortex, cerebellum, thalamus, and brainstem. Downregulation of p19INK4d in the dentate gyrus after kainic acid-induced seizures indicated that its expression could also be modified in nondividing cells by excitotoxic stress. Therefore, p19INK4d may contribute to maintaining the quiescent state, acting as a buffer to prevent reactivation of cyclin D-dependent kinases in terminally differentiated cells.     

Malignoma versus bacterial spondylodiscitis: value of spinal MRI for the differential diagnosis in an emergency situation. Description in an acute case with progressive paraplegia

BACKGROUND: For the radiation oncologist in an emergency situation with acute progressive paraplegia distinguishing between benign versus malignant vertebral compression fracture without known malignoma may cause a severe diagnostic problem, when a rapid therapeutic decision is required. PATIENT AND METHOD: A case of an elderly diabetic patient with acute onset of a progressive neurologic deficit is reported. No malignancy was known so far. The CT of the spine showed a destruction of the 7th and 8th thoracic vertebral body with compression of the spinal cord. The patient was referred to the radiotherapist for radiation of a presumed malignant spinal process. RESULT: For differential diagnosis a magnetic resonance imaging (MRI) of the spine was performed and could lead to the correct diagnosis of an infectious spondylodiscitis. CONCLUSION: The MRI of the spine has a potential role for correct differentiation between benign and malignant spinal lesions and may thereby assist the radiotherapist in the decision making in an emergency situation.     

Expression of topoisomerase II, bcl-2, and p53 in three human brain tumor cell lines and their possible relationship to intrinsic resistance to etoposide

We characterized three human brain tumor cell lines (D54, HBT-20, and HBT-28) with respect to resistance to etoposide (VP-16), a topoisomerase II-reactive drug. All three cell lines were inherently resistant to VP-16 when compared to other human cell lines, with D54 showing the greatest resistance using colony formation assays. Resistance to VP-16 has been attributed to decreased drug uptake and changes in topoisomerase II; however, drug uptake and topoisomerase II protein levels (immunoblot) were no lower in D54 than in HBT-20 and HBT-28, cell lines relatively more sensitive to VP-16. More to the point, measurement of topoisomerase II-mediated DNA cleavage of cellular DNA after treatment with VP-16 showed that the topoisomerase II in these cells was active. These data indicate mechanisms other than those attributable to decreased drug uptake or altered topoisomerase II exist for clinical resistance to VP-16. VP-16-induced DNA cleavage has been associated with apoptosis in some cell lines; however, neither DNA laddering nor morphological changes characteristic of apoptosis were detected in these cell lines after treatment with VP-16. Bcl-2 and mutant p53 were present in these cells. Either of these conditions can prevent apoptosis and could explain a dissociation between the proximal mediator of VP-16-induced cytotoxicity (topoisomerase II-DNA complex formation) and cellular death.     

Si/SiGe n-MODFETs on thin SiGe virtual substrates prepared by means of He implantation

Si/SiGe n-type modulation-doped field-effect transistors grown on a very thin strain-relieved Si/sub 0.69/Ge/sub 0.31/ buffer on top of a Si(100) substrate were fabricated and characterized. This novel type of virtual substrate has been created by means of a high dose He ion implantation localized beneath a 95-nm-thick pseudomorphic SiGe layer on Si followed by a strain relaxing annealing step at 850/spl deg/C. The layers were grown by molecular beam epitaxy. Electron mobilities of 1415 cm/sup 2//Vs and 5270 cm/sup 2//Vs were measured at room temperature and 77 K, respectively, at a sheet carrier density of about 3/spl times/10/sup 12//cm/sup 2/. The fabricated transistors with Pt-Schottky gates showed good dc characteristics with a drain current of 330 mA/mm and a transconductance of 200 mS/mm. Cutoff frequencies of f/sub t/=49 GHz and f/sub max/=95 GHz at 100 nm gate length were obtained which are quite close to the figures of merit of a control sample grown on a conventional, thick Si/sub 0.7/Ge/sub 0.3/ buffer.