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Biomedical subjects

J H Eggert

Publications and source records attributed to J H Eggert.

At least 19 recordsLinked to original sources
PubMed2006

Dissociation of liquid silica at high pressures and temperatures.

Liquid silica at high pressure and temperature is shown to undergo significant structural modifications and profound changes in its electronic properties. Temperature measurements on shock waves in silica at 70-1,000 GPa indicate that the specific heat of liquid rises SiO(2) well above the Dulong-Petit limit, exhibiting a broad peak with temperature that is attributable to the growing structural disorder caused by bond breaking in the melt. The simultaneous sharp rise in optical reflectivity of liquid SiO(2) indicates that such dissociation causes the electrical and therefore thermal conductivities of silica to attain metalliclike values of 1-5 x 10(5) S/m and 24-600 W/m x K, respectively.

Journal Article↗
PubMed2005

EXAFS measurement of iron bcc-to-hcp phase transformation in nanosecond-laser shocks.

Extended x-ray absorption fine structure (EXAFS) measurements have demonstrated the phase transformation from body-centered-cubic (bcc) to hexagonal-close-packed (hcp) iron due to nanosecond, laser-generated shocks. The EXAFS spectra are also used to determine the compression and temperature in the shocked iron, which are consistent with hydrodynamic simulations and with the compression inferred from velocity interferometry. This is a direct, atomic-level, and in situ proof of shock-induced transformation in iron, as opposed to the previous indirect proof based on shock-wave splitting.

Journal Article↗
PubMed2005

Direct observation of the alpha-epsilon transition in shock-compressed iron via nanosecond x-ray diffraction.

In situ x-ray diffraction studies of iron under shock conditions confirm unambiguously a phase change from the bcc (alpha) to hcp (epsilon) structure. Previous identification of this transition in shock-loaded iron has been inferred from the correlation between shock-wave-profile analyses and static high-pressure x-ray measurements. This correlation is intrinsically limited because dynamic loading can markedly affect the structural modifications of solids. The in situ measurements are consistent with a uniaxial collapse along the [001] direction and shuffling of alternate (110) planes of atoms, and are in good agreement with large-scale nonequilibrium molecular dynamics simulations.

Journal Article↗
PubMed2004

Shock compressing diamond to a conducting fluid.

Laser generated shock reflectance data show that diamond undergoes a continuous transition from optically absorbing to reflecting between Hugoniot pressures 600<P(H)<1000 GPa. The data are consistent with diamond having a thermal population of carriers at P(H) approximately 600 GPa, undergoing band overlap metallization at P(H) approximately 1000 GPa and melting at 800<P(H)<1000 GPa. The results agree well with an equation of state model that predicts that elemental carbon remains solid throughout the interior of Neptune.

Journal Article↗
PubMed2003

Shock-induced transformation of Al2O3 and LiF into semiconducting liquids.

Shock compression of sapphire (Al2O3) and lithium fluoride (LiF) to pressures above 5 Mbar has been observed to transform these transparent, wide band-gap insulators into partially degenerate liquid semiconductors with optical reflectivities of several percent. Reflectivities rise steadily with shock pressure up to 45% in sapphire at 20 Mbar and 20% in LiF at 13 Mbar. Using a simple model, the electron scattering length was inferred to be approximately the interatomic distance. In addition, several equation-of-state points at these pressures were measured.

Journal Article↗
PubMed1999

Pressure-enhanced ortho-para conversion in solid hydrogen up to 58 GPa.

We measured the ortho-para conversion rate in solid hydrogen by using Raman scattering in a diamond-anvil cell, extending previous measurements by a factor of 60 in pressure. We confirm previous experiments that suggested a decrease in the conversion rate above about 0.5 GPa. We observe a distinct minimum at 3 GPa followed by a drastic increase in the conversion rate to our maximum pressure of 58 GPa. This pressure enhancement of conversion is not predicted by previous theoretical treatments and must be due to a new conversion pathway.

Journal Article↗
PubMed1986

Isolation and characterization of A41030, a complex of novel glycopeptide antibiotics. Application of the Michel-Miller high performance low pressure liquid chromatography system.

A new antibiotic complex, designated A41030, has been isolated from the fermentation broth of Streptomyces virginiae. Factors A, B, C, D, E, F and G were separated by an efficient preparative high performance low pressure liquid chromatography system. The apparatus offers economic reversed phase separations on glass columns. The A41030 factors are members of the general class of glycopeptide antibiotics and are active in vitro and in vivo vs. Gram-positive bacteria.

Anti-Bacterial Agents↗
PubMed1986

[Surgical therapy of regional lymph nodes in cancers of the lower lip].

Based on a retrospective follow-up study of patients with lower-lip carcinoma from 1968 to 1980, the incidence of metastases of such lesions was broken down according to tumor classification, and the survival rates for these patients were computed. In the total group of 89 patients with primary surgical treatment of the tumor and lymph nodes, 17 (19.1%) were found to have metastases. Among these tumors, 5 were classified as T1, 10 as T2, and 2 as T3. Analysis of the survival rate yielded the following results. To date, there has been no recurrence in any of the patients who underwent suprahyoid lymph-node removal with no histological evidence of lymph-node metastases. Of the 17 patients in whom histological lymph-node metastases were identified in the submandibular region following primary suprahyoid neck dissection, 64.7% showed no evidence of disease for 5 years on average, and all are still alive. In contrast, 90% of the patients died in whom the primary tumor was just treated locally and who did not undergo radical removal of the suprahyoid lymph-node until secondary metastases had occurred. In the light of our experience, suprahyoid lymph-node removal appears to be indicated as part of the primary treatment of lower-lip carcinoma, independent of the prevailing tumor stage. This may not apply to tumors that are clearly less than 1 cm in size.

Humans↗
PubMed1984

The versatility of modern therapy in mid-facial trauma.

Modern trends in the therapy of mid-facial trauma, which include the use of miniplates, wire osteosynthesis, and suspension wiring, bone transplantation from the contra-lateral canine fossa for orbital floor reconstruction, as well as the use of lyophilised dura placed over bony defects, are briefly discussed. The versatility of the combined techniques used in therapy has been illustrated by a case.

Adult↗