Support Possibilities for 3D Scanning of Forging Tools with Deep and Slim Impressions for an Evaluation of Wear by Means of Replication Methods

This article discusses the problems related to the use of non-contact 3D scanning techniques and their support by means of replication methods for the analysis of the geometrical changes in deep tool impressions used for the forward extrusion of valve-type elements assigned for motor truck engines. The 3D scanning method, despite its unquestionable advantages, also has certain limitations, such as scanning the inner surfaces of deep cavities. This is caused by the fact that the larger the angle between the reflected laser light and the normal direction to the measured surface, the larger the area covered for the analysis, yet at the same time, the higher the measurement error. The authors performed an analysis of the geometrical loss of the tools as well as the corresponding replication masses, together with a discussion of the results related to minimization of the measuring errors. For the analyzed tool, the maximum angle during direct scanning was 40 degrees, which unfortunately does not enable an analysis of the entire pattern, while for larger angles, it is necessary to make the measurement by indirect scanning, i.e., by replicating the cavity imprint of the tool. Therefore, for a given geometry, the reflection angle should be determined individually.

The unexpected racemization and hydrogen–deuterium exchange of the hydrogen at the α-carbon of proline analogs containing the 5-azoniaspiro[4.4]nonyl-group

Herein, we present an unexpected racemization and the hydrogen–deuterium exchange (HDX) at the α-C atom of the proline derivative under basic aqueous conditions (1% water solution of triethylamine).

Strain accumulation in the shumagin and yakataga seismic gaps, alaska

Strain accumulation during the 1980-85 interval has been measured by means of trilateration surveys in the Shumagin and Yakataga seismic gaps, which are the two regions identified as the most likely sites for the next great thrust earthquakes along the Alaska-Aleutian arc. No significant strain accumulation was detected in the Shumagin gap, but experience at similar subduction zones and simple models of the subduction process suggest that a measurable amount of strain should have accumulated. The most likely explanation of the observation is that subduction there is either aseismic or episodic. The strain accumulation measured in the Yakataga gap is consistent with that expected for the plate convergence rate, although the direction of maximum compression may suggest a somewhat more oblique convergence than expected.

Nonequilibrium magnetization dynamics of gadolinium studied by magnetic linear dichroism in time-resolved 4f core-level photoemission

The magnetic linear dichroism of the gadolinium 4f core level is studied in a time-resolved photoemission experiment employing laser pump- and synchrotron-radiation probe pulses. Upon optical excitation of the 5d6s valence electrons with femtosecond laser pulses, the magnetic order in the 4f spin system is reduced. Remarkably, the linear dichroism remains at 80% of the equilibrium contrast while the lattice temperature reaches the Curie temperature due to electron-phonon scattering. Contrasting itinerant ferromagnets, this shows that equilibration between the lattice and spin subsystems takes in Gd about 80 ps and is established in parallel with heat diffusion.

Ultrafast electron relaxation in superconducting Bi(2)Sr(2)CaCu(2)O(8+delta) by time-resolved photoelectron spectroscopy

Time-resolved photoelectron spectroscopy is employed to study the dynamics of photoexcited electrons in optimally doped Bi{2}Sr{2}CaCu{2}O{8+delta} (Bi-2212). Hot electrons thermalize in less than 50 fs and dissipate their energy on two distinct time scales (110 fs and 2 ps). These are attributed to the generation and subsequent decay of nonequilibrium phonons, respectively. We conclude that 20% of the total lattice modes dominate the coupling strength and estimate the second momentum of the Eliashberg coupling function lambdaOmega{0}{2}=360+/-30 meV{2}. For the typical phonon energy of copper-oxygen bonds (Omega{0} approximately 40-70 meV), this results in an average electron-phonon coupling lambda<0.25.

Genetic evaluation of laying hens under fixed regression animal models

Abstract. Monthly egg production in laying hens was studied under fixed regression models. The data of 37071 birds from three strains under long term selection were analysed. The covariates from four production curves were included in nested and non-nested form. From linearized functions the model of Ali and Schaeffer most adequately described the egg production. Akaike Information Criterion favoured models with nested covariates. The following genetic parameters were estimated: heritability 0.02–0.2, 0.03–0.06, 0.03–0.20 repeatability 0.11–0.23, 0.21–0.30, 0.34–0.43 for A22, A88 and K66 lines, respectively. In conclusion, regression models could be considered in genetic evaluation of laying hens.

Dynamics of the self-energy of the Gd(0001) surface state probed by femtosecond photoemission spectroscopy

Transient changes of the complex self-energy of the 5d(z2) surface state on Gd(0001) after intense optical excitation are investigated by femtosecond time-resolved photoemission. We observe an ultrafast (<100 fs) broadening of the linewidth due to e-e scattering followed by a decrease of the binding energy due to thermal expansion of the lattice. In addition, we resolve a periodic breathing of the band structure which originates from a coherent phonon. An amplitude of 1 pm is derived from the binding energy shift upon lattice displacement calculated by density functional theory.

Sex steroids level in blood plasma and ovarian follicles of the chimeric chicken

The study was performed to determine the hormonal status of mature germline chimeras obtained by blastodermal cell transfer from chicken embryos of a donor breed [Green-legged Partridgelike breed (GP) x Araucana (AR)] to those of a recipient breed [White Leghorn (WL)] being at the same stage of embryonic development. The egg-laying chimeras and WL hens (control) of the same age were used in the experiment. At first, blood samples were taken from each bird at 0.5, 5, 12.5 and 18.5 h following oviposition. Subsequently, the chimeras and the WL hens were decapitated 1-2 h after ovulation. A stroma and the following follicles were isolated from the ovary: white normal (1-4, 4-6 and 6-8 mm), white atretic and yellow preovulatory follicles (F4-F1). Sex hormones, progesterone (P4), testosterone (T) and oestradiol (E2) in blood plasma and ovarian follicles were determined radioimmunologically. The activity of the 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the granulosa and theca layers of the follicles was analysed histochemically. In chimeric chickens, a higher level of T in blood plasma during the ovulatory cycle was noticed. However, in the stroma, white prehierarchical and medium-size preovulatory ovarian follicles the level of T was significantly lower. With respect to E2, its elevated levels were found both in blood and in the ovarian follicles. There were no significant differences in P4 concentrations in blood plasma while in ovarian follicles a higher level was observed only in white 6-8 mm follicles. 3beta-HSD activity in granulosa and theca layers of the ovarian follicles in chimeras was not different from that in the WL hens. In conclusion, the results obtained indicate that germline chimeras exhibit significant alterations in sex hormone levels in the ovary and blood plasma, which in turn may affect their reproductive abilities.

Time evolution of the electronic structure of 1T-TaS2 through the insulator-metal transition

Femtosecond time-resolved photoemission is used to investigate the time evolution of electronic structure in the Mott insulator 1T-TaS2. A collapse of the electronic gap is observed within 100 femtoseconds after optical excitation. The photoemission spectra and the spectral function calculated by dynamical mean field theory show that this insulator-metal transition is driven solely by hot electrons. A coherently excited lattice displacement results in a periodic shift of the spectra lasting for 20 ps without perturbing the insulating phase. This capability to disentangle electronic and phononic excitations opens new directions to study electron correlation in solids.

Femtosecond electron and spin dynamics in Gd(0001) studied by time-resolved photoemission and magneto-optics

Femtosecond electron and spin dynamics of the Gd(0001) surface are investigated by time-resolved photoemission and second harmonic generation. Upon optical excitation the spin polarization of the surface state is reduced by half while its exchange splitting remains nearly unchanged. Electron-magnon interaction is proposed to facilitate electron-spin-flip scattering among spin-mixed surface and bulk states, which provides a mechanism for ultrafast demagnetization.

Synthesis, conformation, and immunosuppressive activity of CLX and its analogues

The CLX peptide isolated from flax seed has a sequence cyclo-(PPFFILLX), where X is a nonproteinaceous amino acid residue, (2S,4R) 4-amine-N-methylproline. Picur, B.; Lisowski, M.; Siemion, I.Z. Letters Pept Sci 1998, 5, 183-187. The structure of X strongly suggests that this natural amino acid plays a role of the dipeptide moiety with a nonplanar cis peptidomimetic bond. The X residue contains two asymmetrical carbons and thus can appear in four configurations: (2S,4R), (2S,4S), (2R,4S), and (2R,4R). All four diastereoisomers of X were synthesized and characterized as trifluoroacetates of 4-phtalimido-N-methylproline benzylamides. Their full physicochemical characteristics are presented in this article. The synthesis of linear and cyclic analogues of CLX containing all four possible diastereoisomers of X was performed. Additionally, analogues with gamma-aminobutyric acid (GABA) and glycyl-N-methyl-glycine dipeptide [G(Me)G] substituted for X were synthesized. The obtained peptides were purified using HPLC, examined by ESI/MS, and then studied by CD spectroscopy. They were also tested for immunosuppressive activity (PFC in vitro). All of them revealed diverse immunosuppressive activity, however, lower than that of cyclolinopeptide A (CLA) Wieczorek, Z.; Bengtsson, B.; Trojnar, J.; Siemion, I.Z. Peptide Res 1991, 4, 275-283. and cyclosporine A (CsA). Ellis, G.P.; West, G.B. Progress Med Chem 1988, 25, 1-33. The structure of CLX with (2S,4R) 4-amino-N-methylproline was determined by 2-D NMR methods. All amide bonds are in the trans configuration. The cis peptidomimetic group delta-CH(2)-N(CH(3))- is exposed to the outside of the CLX molecule. The peptide contains two loops similar to beta-turns of type IV. Chou, P.Y.; Fasman, G.D. J Mol Biol 1977, 115, 136-715 and has the extended shape flanked by F3 and L7 residues with significant side chain flexibility.

Reconstitution of a chicken breed by inter se mating of germline chimeric birds

Blastoderm cells from chicken embryos of a donor breed (Green-legged Partridgelike; GP) were transferred to embryos of a recipient breed (White Leghorn; WL) to form chimeric progeny that, after inter se mating, permitted successful reconstitution of the donor breed. Among 23 chimeric chicks hatched from WL embryos injected with GP cells, 20 (87%) were raised until maturity, and progeny were tested by mating with GP birds to determine the ability of blastodermal cells to form germline chimeras. Six of the tested birds (30%) produced recipient-derived and donor-derived offspring, indicating that they were germline chimeras. The mean percentages of donor-derived germ cells in these birds were 21.1 (17.6 to 50.0%) and 16.9 (5.3 to 23.1%) in males and females, respectively. Among 477 chicks, resulting from mating the germline chimeric male with four germline chimeric females, 10 chicks (2.1%) exhibited a GP phenotype, indicating that the original donor stock had been reconstituted. Only one germline chimeric hen produced GP offspring, but the expected and calculated percentages of GP offspring were similar (2.99 and 2.08, respectively). Two methods of DNA analyses (RFLP and PCR amplification of polymorphic microsatellite loci) of chimeras and their offspring indicated that through mating of a relatively small number of chimeras it is possible to reconstitute a highly diverse population.

Paramagnetic reentrant effect in mesoscopic cylinders made of a normal metal in proximity with a superconductor

We show that the paramagnetic reentrant effect observed in experiments by Mota et al. in mesoscopic cylinders made of a normal metal in proximity with a superconductor, can be caused by paramagnetic persistent currents flowing on the outer shell of the cylinder.

Interactions of the Streptomyces lividans initiator protein DnaA with its target

The Streptomyces lividans DnaA protein (73 kDa) consists, like other bacterial DnaA proteins, of four domains; it binds to 19 DnaA boxes in the complex oriC region. The S. lividans DnaA protein differs from others in that it contains an additional stretch of 120 predominantly acidic amino acids within domain II. Interactions between the DnaA protein and the two DnaA boxes derived from the promoter region of the S. lividans dnaA gene were analysed in vitro using three independent methods: Dnase-I-footprinting experiments, mobility-shift assay and surface plasmon resonance (SPR). The Dnase-I-footprinting analysis showed that the wild-type DnaA protein binds to both DnaA boxes. Thus, as in Escherichia coli and Bacillus subtilis, the S. lividans dnaA gene may be autoregulated. SPR analysis showed that the affinity of the DnaA protein for a DNA fragment containing both DnaA boxes from the dnaA promoter region (KD = 1.25 nM) is 10 times higher than its affinity for the single 'strong' DnaA box (KD = 12.0 nM). The mobility-shift assay suggests the presence of at least two classes of complex containing different numbers of bound DnaA molecules. The above data reveal that the DnaA protein binds to the two DnaA boxes in a cooperative manner. To deduce structural features of the Streptomyces domain II of DnaA protein, the amino acid DnaA sequences of three Streptomyces species were compared. However, according to the secondary structure prediction, Streptomyces domain II does not contain any common relevant secondary structural element(s). It can be assumed that domain II of DnaA protein can play a role as a flexible protein spacer between the N-terminal domain I and the highly conserved C-terminal part of DnaA protein containing ATP-binding domain III and DNA-binding domain IV.

UV-difference and CD spectroscopy studies on juvenile hormone binding to its carrier protein

Juvenile hormone binding protein (JHBP) from hemolymph of Galleria mellonella is a single-chain glycoprotein of molecular mass near 25,880 containing no Trp residues. The fourth derivative of the protein absorption spectrum shows the characteristic vibrational components of the phenylalanine spectrum within the range 240-270 nm. At longer wavelengths two main bands 0-0 and 0+800 cm(-1) appear, caused by vibrational levels of electronic transition, pi-->pi*, in the tyrosine residues, with maxima at 279 nm and 286 nm, respectively. Two intersection points of the second derivative absorption band with abscissa at about 288.8 nm and 283 nm were analysed for estimation of the environment polarity of Tyr residues in the JHBP molecule. The results obtained suggest that JHBP contains at least two classes of Tyr residues with very apolar environment, similar to that found in azurine. In the JHBP-JH complex only one class of Tyr residues located in a very apolar environment was found, and a small perturbation of disulphide bridges was deduced from the UV-difference spectrum. Ligand perturbation appears as a minimum at 243 nm of the UV-difference spectrum. Comparison of the circular dichroism (CD) spectra for free JHBP with the CD spectra for the JHBP-JH complex monitored in the far-UV (190-240 nm) region indicates rather small differences in the secondary structure of the protein. Although ligand binding induces distinct changes in the near-UV (250-300 nm) region of the CD spectrum of JHBP, it is apparent where both Tyr and Phe residues contribute.

Sulfonated analogues of cyclolinopeptide A. Synthesis, immunosuppressive activity and CD studies

Linear and cyclic analogues of cyclolinopeptide A (CLA) in which one or both phenylalanine residues in fragment Pro6-Pro7-Phe8-Phe9 were substituted by their sulfonated derivatives have been synthesized by SPPS method and cyclization with the BOP reagent. The peptides were examined for their immunosuppressive activity in the humoral and cellular immune response by PFC and DTH tests. All of the analogues retain some immunosuppressive activity of native CLA. Their CD spectra confirm that the optical activity of aromatic residues in CLA depends on their position in the peptide chain. Only the residue in position 8 seems to be optically active. CD spectrum of the cyclic analogue modified in position 9 is very similar to that of native CLA which correlates with its high biological activity. The chiroptical properties of the p-sulfonated Phe-residue are established.

Conformational investigation of alpha,beta-dehydropeptides. VII. Conformation of Ac-Pro-deltaAla-NHCH3 and Ac-Pro-(E)-deltaAbu-NHCH3: comparison with (Z)-substituted alpha,beta-dehydropeptides

The crystal structure and solution conformation of Ac-Pro-deltaAla-NHCH3 and the solution conformation of Ac-Pro-(E)-deltaAbu-NHCH3 were investigated by X-ray diffraction method and NMR, FTIR and CD spectroscopies. Ac-Pro-deltaAla-NHCH3 adopts an extended-coil conformation in the crystalline state, with all-trans peptide bonds and the deltaAla residue being in a C5 form, phi(1)=-71.4(4), psi(1)=-16.8(4), phi(2)= -178.4(3) and psi(2)= 172.4(3) degrees. In inert solvents the peptide also assumes the C5 conformation, but a gamma-turn on the Pro residue cannot be ruled out. In these solvents Ac-Pro-(E)-deltaAbu-NHCH3 accommodates a beta(II)-turn, but a minor conformer with a nearly planar disposition of the CO-NH and C=C bonds (phi(2) approximately 0 degrees) is also present. Previous spectroscopic studies of the (Z)-substituted dehydropeptides Ac-Pro-(Z)-deltaAbu-NHCH3 and Ac-Pro-deltaVal-NHCH3 reveal that both peptides prefer a beta(II)-turn in solution. Comparison of conformations in the family of four Ac-Pro-deltaXaa-NHCH3 peptides let us formulate the following order of their tendency to adopt a beta-turn in solution: (Z)-deltaAbu > (E)-deltaAbu > deltaVal; deltaAla does not. None of the folded structures formed by the four compounds is stable in strongly solvating media.

New proctolin analogues modified by D-amino acids in the peptide chain and their high cardioexcitatory effect on Tenebrio molitor

The object of our studies was the synthesis and conformational and biological evaluation of the series of 14 analogues of the insect neuropeptide, proctolin. The analogues were obtained by replacement of the native L-amino acids by their D-isomers in one, two, and all positions. Biological effects of the peptides were examined by cardioexcitatory test on the heart of yellow mealworm, Tenebrio molitor, in vitro. In biotest performed on insects, D-Arg-D-Tyr-D-Leu-D-Pro-D-Thr, [D-Arg(N-G-nitro)1,D-Leu3]-, [D-Arg1,D-Leu3]-, [D-Tyr2,D-Thr5]- and [D-Arg1,D-Pro4]-proctolin exert high agonistic activity of proctolin on the heart of insects at 10(-11) - 10(-10) M concentrations. The proctolin analogue containing only D-amino acid residues in the peptide chain unexpectedly shows a much higher cardioexcitatory effect than the native peptide. Moreover, preliminary CD and NMR conformational studies show that proctolin analogues investigated here seem to prefer rather ordered structures, although their conformations differ in some cases.

Comparison of thermodynamic and kinetic effects between the Leu32-->norvaline and Leu35-->norvaline substitutions of the three-fragment complex of cytochrome c

The three fragment complex (1-25)H.(28-38).(39-104) of horse cytochrome c (e.g., (1-25)H, the heme fragment containing residues 1 to 25) closely resembles the native protein except for residues 39 to 55, which are flexible. We have investigated how the Leu35-->Nva (norvaline) substitution differs from the Leu32-->Nva in the perturbation of the stability of this complex. The side chains of Leu32 and Leu35 are adjacent in the well-packed hydrophobic core of tuna cytochrome c (T. Takano and R. E. Dickerson (1981) J. Mol. Biol. 153, 95-115). We measured the effects of the substitutions on (i) the binding of (28-38) with ferri- and ferrocomplexes on the right side of the heme (Dickerson's orientation); (ii) the heat stability of the 695-nm band which monitors the Fe-S bond on the left side of the heme (cf. Takano and Dickerson, 1981); and (iii) the rate constant for the direct dissociation of (39-104) of the ferrous complex as a function of temperature. The results suggest that the Leu32-->Nva is unique in that the stabilizing energy associated with the ground state is markedly more perturbed in the Leu32-->Nva than in the Leu35-->Nva. This is true despite the fact that both substitutions introduce no stereochemical conflict and remove only the gamma-methyl groups of the Leu side chains which are presumably positioned adjacently with respect to each other in the core. Furthermore, the effect of the perturbation of the structure imposed by the removal of the Leu32 gamma-methyl group propagates itself perhaps through the core and affects the stability of the Fe-S bond and the binding strength of (39-104). These properties resemble the core domain-domain interaction (A. Fisher and H. Taniuchi (1992) Arch. Biochem. Biophys. 296, 1-16).

Does the edge-to-face interaction between aromatic rings occur in cyclolinopeptide A analogues?

We measured 1H-NMR, fluorescence and CD spectra of cyclolinopeptide A (CLA), its tyrosine analogues with each or both phenylalanines substituted by tyrosine (c-[LeuIleIleLeuValProProTyrPhe], c-[LeuIleIleLeuValProProPheTyr] and c-[LeuIleIleLeuValProProTyrTyr]), and their linear counterparts with the starting sequence leu-Ile-Ile-Leu-Val-Pro-Pro-Phe-Phe (LA). It follows from CD spectra that the conformations of all cyclic peptides are similar to that of CLA; the conformations of linear peptides are more diversified, with the conformation of [Tyr9]LA being most similar to CLA. NMR studies suggest that aromatic rings in cyclic peptides are situated perpendicular to each other, manifesting edge-to-face pairing. Accordingly, the residue in position 9 is shielded ('edge'), and a residue in position 8 is the shielding one ('face'). This effect is not present in the case of linear peptides. Fluorescence quantum yields were much lower for cyclic peptides than for linear ones, indicating the interaction of closely located aromatic chromophores. Those quantum yields depend on the relative position of Tyr in the peptide chain. Another factor influenced by the position in the peptide chain is the optical activity of aromatic side chains (optically active in position 8, inactive in position 9). This phenomenon could be explained by the differences in the side-chain conformation of both aromatic residues.

A dramatic change in the interaction of Cu(II) with bio-peptides promoted by SDS--a model for complex formation on a membrane surface

The extent of complex formation between Cu(II) and many biologically active oligopeptides has been shown to change significantly in the presence of SDS micelles, a recognized model for cell lipid membranes. Protonation constants of peptides can be increased by up to 2 log unit, especially when they contain hydrophobic side chains. Metal complex formation is generally less extensive and the conformations of peptides can be altered dramatically when compared to those in simple aqueous solution.

Conformational investigation of alpha, beta-dehydropeptides. V*. Stability of reverse turns in saturated and alpha, beta-unsaturated peptides Ac-Pro-Xaa-NHCH3: CD studies in various solvents

Conformations of three series of model peptides: homochiral Ac-Pro-L-Xaa-NHCH3 and heterochiral Ac-Pro-D-Xaa-NHCH3 (Xaa = Phe, Val, Leu, Abu, Ala) as well as alpha, beta-dehydro Ac-Pro-delta Xaa-NHCH3 [delta Xaa = (Z)-delta Phe, delta Val,(Z)-delta Leu,(Z)-delta Abu] were investigated by CD spectroscopy in 2% dichloromethane-cyclohexane, trifluoroethanol, water, and occasionally in other solvents. The spectra of homochiral peptides show a significant solvent dependence. Folded structures are present in 2% dichloromethane-cyclohexane and unordered ones occur in water. The folded conformers are of the inverse gamma-turn type for all the peptides but Ac-Pro-L-Phe-NHCH3 for which the type-I beta-turn is preferred. The changes in the spectra of the heterochiral peptides are limited. The compounds adopt the type-II beta-turn in 2% dichloromethane-cyclohexane, represented by class B spectra, and retain this conformation in water as well as in fluorinated alcohols but not always to a full extent. The CD spectra of the unsaturated peptides in 2% dichloromethane-cyclohexane, although they cannot be assigned to any common spectral class, must be attributed to the beta II-turn conformation as determined for these compounds by NMR and IR spectroscopy. The CD spectra of dehydropeptides exhibit a considerable solvent dependence and suggest unordered structures in water.

The Cape Mendocino, California, Earthquakes of April 1992: Subduction at the Triple Junction

The 25 April 1992 magnitude 7.1 Cape Mendocino thrust earthquake demonstrated that the North America-Gorda plate boundary is seismogenic and illustrated hazards that could result from much larger earthquakes forecast for the Cascadia region. The shock occurred just north of the Mendocino Triple Junction and caused strong ground motion and moderate damage in the immediate area. Rupture initiated onshore at a depth of 10.5 kilometers and propagated up-dip and seaward. Slip on steep faults in the Gorda plate generated two magnitude 6.6 aftershocks on 26 April. The main shock did not produce surface rupture on land but caused coastal uplift and a tsunami. The emerging picture of seismicity and faulting at the triple junction suggests that the region is likely to continue experiencing significant seismicity.

Immunosuppressive analogues of hexapeptide Tyr-Val-Pro-Leu-Phe-Pro, an immune system stimulant

It was found that substitution of Val2 and/or Leu4 residue in a hexapeptide Tyr-Val-Pro-Leu-Phe-Pro (I) transforms this peptide immunostimulant into analogues possessing the immunosuppressor activity--Tyr-Gly-Pro-Leu-Phe-Pro (II), Tyr-Val-Pro-Gly-Phe-Pro (III), and Tyr-Gly-Pro-Gly-Phe-Pro (IV). Biological effects of peptides I-IV were studied using PFC (plaque forming cell) test, GvH (graft vs host) reaction in mice, and ARFC (autologous rosette forming cell) test. The strongest immunosuppressor activity was observed for III--in this case the immunosuppressor effect was observed even in PFC test in vitro in which II and IV showed no such activity. These results suggest that simultaneous presence of both Val2 and Leu4 residues is necessary for the generation of immunostimulation. The CD study of I-IV in methanol solution suggests that the conformational preferences of II-IV change towards stabilization of the beta-turn structure, whereas in the case of I the gamma-turn on Leu4 and cis' orientation of the Pro3 carbonyl (distorted beta-turn of type I) was found as the preferred conformation. Competition in biological effects observed for I and III in PFC in vitro test suggests that these analogues may interact with the same cellular receptor. Drastic changes in the activity which accompany changes in the sequence are discussed in the terms of our stereochemical hypothesis.

Strain Measurements and the Potential for a Great Subduction Earthquake Off the Coast of Washington

Geodetic measurements of deformation in northwestern Washington indicate that strain is accumulating at a rate close to that predicted by a model of the Cascadia subduction zone in which the plate interface underlying the continental slope and outer continental shelf is currently locked but the remainder of the interface slips continuously. Presumably this locked segment will eventually rupture in a great thrust earthquake with a down-dip extent greater than 100 kilometers.

Surface Displacements in the 1906 San Francisco and 1989 Loma Prieta Earthquakes

The horizontal displacements accompanying the 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake are computed from geodetic survey measurements. The 1906 earthquake displacement field is entirely consistent with right-lateral strike slip on the San Andreas fault. In contrast, the 1989 Loma Prieta earthquake exhibited subequal components of strike slip and reverse faulting. This result, together with other seismic and geologic data, may indicate that the two earthquakes occurred on two different fault planes.