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Intense X-ray free-electron lasers (XFELs) can rapidly excite matter, leaving it in inherently unstable states that decay on femtosecond timescales. The relaxation occurs primarily via Auger emission, so excited-state observations are constrained by Auger decay. In situ measurement of this process is therefore crucial, yet it has thus far remained elusive in XFELs owing to inherent timing and phase jitter, which can be orders of magnitude larger than the timescale of Auger decay. Here we develop an approach termed ‘self-referenced attosecond streaking’ that provides subfemtosecond resolution in spite of jitter, enabling time-domain measurement of the delay between photoemission and Auger emission in atomic neon excited by intense, femtosecond pulses from an XFEL. Using a fully quantum-mechanical description that treats the ionization, core-hole formation and Auger emission as a single process, the observed delay yields an Auger decay lifetime of 2.2−0.3+0.2fs for the KLL decay channel.

It is well known that a fiber taper—an optical fiber whose size varies along its length—must exceed a certain minimum length to be adiabatic and low-loss. In contrast, we show that an optical fiber with a logarithmic refractive index profile can be adiabatically tapered over any length, however short. Its mode field distribution is independent of the fiber’s size and so remains the same along a taper. We report an experimental fiber in which tapers shorter than 2 mm can have losses as low as 0.03 dB. The fiber is compatible with standard telecoms fiber but with low bend loss and should have applications where it is desirable to make tapered fiber components (such as fused couplers and photonic lanterns) as short as possible. The index profile is analogous to the logarithmic potential of quantum mechanics.

We determine the metallicity distribution function (MDF) of the Galactic halo by means of a sample of 1638 metal-poor stars selected from the Hamburg/ESO objective-prism survey (HES). The sample was corrected for minor biases introduced by the strategy for spectroscopic follow-up observations of the metal-poor candidates, namely “best and brightest stars first”. Comparison of the metallicities [Fe/H] of the stars determined from moderate-resolution (i.e., $R\sim 2000$) follow-up spectra with results derived from abundance analyses based on high-resolution spectra (i.e., $R>20\,000$) shows that the [Fe/H] estimates used for the determination of the halo MDF are accurate to within 0.3 dex, once highly C-rich stars are eliminated. We determined the selection function of the HES, which must be taken into account for a proper comparison between the HES MDF with MDFs of other stellar populations or those predicted by models of Galactic chemical evolution. The latter show a reasonable agreement with the overall shape of the HES MDF for ${\rm [Fe/H]} > -3.6$, but only a model of Salvadori et al. (2007) with a critical metallicity for low-mass star formation of $Z_{\rm cr}=10^{-3.4}~Z_{\odot}$reproduces the sharp drop at ${\rm [Fe/H]} \sim -3.6$present in the HES MDF. Although currently about ten stars at ${\rm [Fe/H]} < -3.6$are known, the evidence for the existence of a tail of the halo MDF extending to ${\rm [Fe/H]} \sim -5.5$is weak from the sample considered in this paper, because it only includes two stars ${\rm [Fe/H]} < -3.6$. Therefore, a comparison with theoretical models has to await larger statistically complete and unbiased samples. A comparison of the MDF of Galactic globular clusters and of dSph satellites to the Galaxy shows qualitative agreement with the halo MDF, derived from the HES, once the selection function of the latter is included. However, statistical tests show that the differences between these are still highly significant.

In this work we will present the first measurement of the time history of a collision of two shells in a double shell capsule. Double shell implosions provide a non-cryogenic path to inertial confinement fusion [ICF]. In the double shell target the laser energy is absorbed in an outer shell that is accelerated inward which then, after the laser is off, collides with an inner shell. The inner shell then implodes against the deuterium fuel. We use radiography to diagnose the symmetry and the hydrodynamics of the implosion. At the OMEGA laser at LLE, we point 40 beams in an offset geometry to implode the doube shell target and use the remaining 20 beams to perform radiography from two different directions. This is the first measurement of such a collision in a spherical geometry and is of great interest to the verification of the code we used. In this work we will present the first measurement of the time history of a collision of two spherical shells in a double shell capsule.

In this paper we briefly review the theory of plasma induced line shifts and present some experimental evidence. We then consider the effects that these shifts have on the merging of line series. Influence on continuum lowering is also discussed.

Materials with A2B2O7(pyrochlore) structure have received significant attention for their applications as new protonic conductors and materials used in electronic devices. One of the unique synthesis routes for La2Zr2O7(pyrochlore) powders is the glycine–nitrate combustion method, which shows superior properties of the synthesised powder using glycine as a complexing agent. The Sr doped La2Zr2O7powders in pure pyrochlore structure were produced using this approach. Selected characteristics of the synthesised powders, such as crystal structure, lattice parameters, crystallite size, the vibrational properties, the morphology of the particles, along with the specific surface area and particle size, have been investigated. The dependence of some properties on annealing temperatures of the powders has been studied.

In this work we will present the first measurement of the time history of a collision of two shells in a double shell capsule. Double shell implosions provide a non-cryogenic path to inertial confinement fusion [ICF]. In the double shell target the laser energy is absorbed in an outer shell that is accelerated inward which then, after the laser is off, collides with an inner shell. The inner shell then implodes against the deuterium fuel. We use radiography to diagnose the symmetry and the hydrodynamics of the implosion. At the OMEGA laser at LLE, we point 40 beams in an offset geometry to implode the doube shell target and use the remaining 20 beams to perform radiography from two different directions. This is the first measurement of such a collision in a spherical geometry and is of great interest to the verification of the code we used. In this work we will present the first measurement of the time history of a collision of two spherical shells in a double shell capsule.

Titanium alloy has been used as a material for orthopaedic implants, however drawbacks still exist. Considerable efforts have been taken to modify the surface structure of the implant material and improve the biological performance. Previously we have demonstrated that biomaterials surface modification has a significant effect on the regulation of osteogenesis. We have investigated the behaviour of human osteoclasts on sol-gel coated carbonated hydroxyapatite on anodized titanium alloy. Osteoclasts cultured on the modified surface were able to attach and spread, exhibiting the characteristic peripheral brush border. Successful differentiation of the monocytes into osteoclasts and their attachment to the coated surface and the formation of resorption-like imprints indicated that carbonate hydroxyapatite (CHAP) coated titanium alloy play a significant role in regulating the functional activity of osteoclasts.

AbstractFor thick liquid wall concepts, it is important to understand the different mechanisms affecting the chamber dynamics and the state of the chamber prior to each shot as compared with requirements from the driver and target. These include ablation mechanisms, vapor transport and control, and possible aerosol formation, as well as protective jet behavior. This paper focuses on these research topics and aims at identifying the major issues, assessing the latest results, reviewing the capabilities of existing modeling and experimental facilities with respect to addressing remaining issues, and helping guide future analysis and research and development efforts.

Biomaterials used in bone regeneration are designed to be gradually resorbed by the osteoclast and replaced by new bone formed through osteoblastic activity. The aim of the present study is to analyze the role of osteoclasts in the resorption process. The attachment of human osteoclasts and the appearance of their resorption lacunae, when cultured on either the resorbable crystalline, calcium orthophosphate materials or on the long-term stable bioceramic material was investigated. The resorbable materials contain Ca10[K,Na](PO4)7(AW-Si) and Ca2KNa(PO4)2(GB14, GB9 & D9/25) as their main crystal phases, however they differ in their total solubility. These differences result from small variations in the composition. The long-term stable material consist of about 30% fluorapatite beside calcium zirconium phosphate (Ca5(PO4)3F + CaZr4(PO4)6) and shows a very small solubility. AW-Si has an alkali containing crystalline phase, Ca10[K,Na](PO4). While GB14, GB9 and D9/25 contain the crystalline phase Ca2KNa(PO4)2with small additions of crystalline and amorphous diphosphates and/or magnesium potassium phosphate (GB14). D9/25 and AW-Si is less soluble compared to GB14, and GB9 among the resorbable materials. Resorbable and long-term stable materials vary in their chemical compositions, solubility, and surface morphology. Osteoclasts modified the surface in their attempts to resorb the materials irrespective of the differences in their physical and chemical properties. The depth and morphology of the resorption imprints were different depending on the type of material. These changes in the surface structure created by osteoclasts are likely to affect the way osteoblasts interact with the materials and how bone is subsequently formed.Biomaterials used in bone regeneration are designed to be gradually resorbed by the osteoclast and replaced by new bone formed through osteoblastic activity. The aim of the present study is to analyze the role of osteoclasts in the resorption process. The attachment of human osteoclasts and the appearance of their resorption lacunae, when cultured on either the resorbable crystalline, calcium orthophosphate materials or on the long-term stable bioceramic material was investigated. The resorbable materials contain Ca10[K,Na](PO4)7(AW-Si) and Ca2KNa(PO4)2(GB14, GB9 & D9/25) as their main crystal phases, however they differ in their total solubility. These differences result from small variations in the composition. The long-term stable material consist of about 30% fluorapatite beside calcium zirconium phosphate (Ca5(PO4)3F + CaZr4(PO4)6) and shows a very small solubility. AW-Si has an alkali containing crystalline phase, Ca10[K,Na](PO4). While GB14, GB9 and D9/25 contain the crystalline phase Ca2KNa(PO4)2with small additions of crystalline and amorphous diphosphates and/or magnesium potassium phosphate (GB14). D9/25 and AW-Si is less soluble compared to GB14, and GB9 among the resorbable materials. Resorbable and long-term stable materials vary in their chemical compositions, solubility, and surface morphology. Osteoclasts modified the surface in their attempts to resorb the materials irrespective of the differences in their physical and chemical properties. The depth and morphology of the resorption imprints were different depending on the type of material. These changes in the surface structure created by osteoclasts are likely to affect the way osteoblasts interact with the materials and how bone is subsequently formed.

AbstractA thin-liquid-wall configuration combines the attractive features of a solid wall with the advantages of a renewable armor to accommodate the threat spectra produced by inertial fusion energy targets. Key design issues for successful implementation of the thin-liquid-film wall protection schemes are the reestablishment of the thin liquid armor and the state of the chamber environment prior to each shot relative to the requirements imposed by the driver and target thermal and injection control. Experimental and numerical studies have been conducted to examine the fluid dynamic aspects of thin-liquid-film protection systems with either radial injection through a porous first wall or forced flow of a thin liquid film tangential to a solid first wall. Analyses were also conducted to help assess and understand key processes influencing the chamber environment, including ablation mechanisms that could lead to aerosol formation and the behavior of such aerosol in the chamber. Results from these studies are described in this paper.

AbstractThe ARIES-IFE study was an integrated study of inertial fusion energy (IFE) chambers and chamber interfaces with the driver and target systems. Detailed analysis of various subsystems was performed parametrically to uncover key physics/technology uncertainties and to identify constraints imposed by each subsystem. In this paper, these constraints (e.g., target injection and tracking, thermal response of the first wall, and driver propagation and focusing) were combined to understand the trade-offs, to develop operational windows for chamber concepts, and to identify high-leverage research and development directions for IFE research. Some conclusions drawn in this paper are (a) the detailed characterization of the target yield and spectrum has a major impact on the chamber; (b) it is prudent to use a thin armor instead of a monolithic first wall for dry-wall concepts; (c) for dry-wall concepts with direct-drive targets, the most stringent constraint is imposed by target survival during the injection process; (d) for relatively low yield targets (<250 MJ), an operational window with no buffer gas may exist; (e) for dry-wall concepts with indirect-drive targets, a high buffer gas pressure would be necessary that may preclude propagation of the laser driver and require assisted pinch transport for the heavy-ion driver; and (f) generation and transport of aerosols in the chamber is the key feasibility issue for wetted-wall concepts.

AbstractThe chamber wall armor is subject to demanding conditions in inertial fusion energy (IFE) chambers. IFE operation is cyclic in nature, and key issues are (a) chamber evacuation to ensure that after each shot the chamber returns to a quiescent state in preparation for the target injection and the firing of the driver for the subsequent shot and (b) armor lifetime that requires that the armor accommodate the cyclic energy deposition while providing the required lifetime. Armor erosion would impact both of these requirements. Tungsten and carbon are considered as armor for IFE dry-wall chambers based on their high-temperature and high-heat-flux accommodation capabilities. This paper assesses the requirements on armor imposed by the operating conditions in IFE, including energy deposition density, time of deposition, and frequencies; describes their impact on the performance of the candidate armor materials; and discusses the major issues.

Abstract.: Over the past decade there have been major advances in our understanding of the factors that regulate osteoclast formation and activity. It is now apparent that receptor activator NFκB (RANK), its ligand, RANKL (also known as TRANCE, osteoclast differentiation factor and osteoprotegerin (OPG) ligand) and the natural RANKL inhibitor, OPG, are the key factors regulating osteoclast formation in normal bone physiology. The molecular interactions of these molecules regulate osteoclast formation and subsequent bone loss in disease and there is now strong evidence that the bone loss associated with inflammatory diseases, such as rheumatoid arthritis, periodontal disease and peri-implant loosening, is regulated by the action of RANK, RANKL, and OPG. These molecules are targets for the pharmacological regulation of severe bone loss in several common inflammatory diseases.

A coordinated, focused effort is underway to develop Laser Inertial Fusion Energy. The key components are developed in concert with one another and the science and engineering issues are addressed concurrently. Recent advances include: target designs have been evaluated that show it could be possible to achieve the high gains (>100) needed for a practical fusion system.These designs feature a low-density CH foam that is wicked with solid DT and over-coated with a thin high-Z layer. These results have been verified with three independent one-dimensional codes, and are now being evaluated with two- and three-dimensional codes. Two types of lasers are under development: Krypton Fluoride (KrF) gas lasers and Diode Pumped Solid State Lasers (DPSSL). Both have recently achieved repetitive ‘first light’, and both have made progress in meeting the fusion energy requirements for durability, efficiency, and cost. This paper also presents the advances in development of chamber operating windows (target survival plus no wall erosion), final optics (aluminium at grazing incidence has high reflectivity and exceeds the required laser damage threshold), target fabrication (demonstration of smooth DT ice layers grown over foams, batch production of foam shells, and appropriate high-Z overcoats), and target injection (new facility for target injection and tracking studies).

ABSTRACTAn inertial fusion energy (IFE) wetted wall configuration provides the advantage of a renewable armor to accommodate the threat spectra. Key issues are the re-establishment of the thin liquid armor and the state of the chamber environment prior to each shot relative to the requirements imposed by the driver and target thermal and injection control.

Various surface modifications have been applied to titanium alloy Ti6Al4V implants, in an attempt to enhance osseointegration; crucial for ideal prosthetic fixation. Despite the numerous studies demonstrating that peptidemodified surfaces influence in vitrocellular behavior, there is relatively little data reporting their effects on bone remodeling. The objective of this article was to examine the effects of chemically modifying Ti6Al4V surfaces with a common RGD sequence, a 15residue peptide containing GRGDSP glycinearginineglycineaspartateserineproline, on the modulation of bone remodeling. The expression of proteins known to be associated with osseous matrix and bone resorption were studied during the growth of human bonederived cells HBDC on these peptidemodified surfaces. HBDC grown for 7 days on RGD surfaces displayed significantly increased levels of osteocalcin, and procollagen Iα1 mRNAs, compared with the production by HBDC grown on the native Ti6Al4V. A pattern that was also reflected at the protein levels for osteocalcin, type I collagen, and bone sialoprotein. Moreover, HBDC grown for 7 and 14 days on RGDmodified Ti6Al4V expressed significantly higher level of osteoclast differentiation factors and lower levels of osteoprotegerin and IL6 proteins compared with other surfaces tested. These results suggest that different chemical treatments of implant material Ti6Al4V surface result in differential bone responses, not only their ability to form bone but also to stimulate osteoclastic formation. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 105–113, 2003

We present the time-resolved phosphorescence of oxytocin, two oxytocin derivatives, vasopressin and a series of compounds that serve as models for free tyrosine. One of the oxytocin derivatives, desaminodicarbaoxytocin, has the disulfide bridge replaced by an ethylene bridge, and lacks the N-terminus. Similar to the reported fluorescence decays of tyrosine in these peptides, the phosphorescence decays generally are not single exponentials, but can be fit as biexponentials. The decay times for the oxytocin peptides are shorter than for desaminodicarbaoxytocin or the model compounds, and this we attribute to enhanced spin-orbit coupling due to the presence of sulfur. We measured the phosphorescence decay of the model cyclic pentapeptide that contains tyrosine and compared it to that observed for the same cyclic pentapeptide in which tyrosine is replaced by tryptophan. We also report the phosphorescence of 2-tryptophan-oxytocin, and deamino-2-tryptophan-oxytocin in which biexponential phosphorescence decay is also observed.

Extensive osteolysis adjacent to implants is often associated with wear particles of prosthetic material. We have investigated if RANKL, also known as osteoprotegerin ligand, osteoclast differentiation factor or TRANCE, and its natural inhibitor, osteoprotegerin (OPG), may be important in controlling this bone loss.Cells isolated from periprosthetic tissues containing wear particles expressed mRNA encoding for the pro-osteoclastogenic molecules, RANKL, its receptor RANK, monocyte colony-stimulating factor (M-CSF), interleukin (IL)-1ß, tumour necrosis factor (TNF)a, IL-6, and soluble IL-6 receptor, as well as OPG. Osteoclasts formed from cells isolated from periprosthetic tissues in the presence and absence of human osteoblastic cells. When osteoclasts formed in the absence of osteoblastic cells, markedly higher levels of RANKL mRNA relative to OPG mRNA were expressed. Particles of prosthetic materials also stimulated human monocytes to express osteoclastogenic molecules in vitro.Our results suggest that ingestion of prosthetic wear particles by macrophages results in expression of osteoclast-differentiating molecules and the stimulation of macrophage differentiation into osteoclasts.

Objective. This study investigated the involvement of the recently identified regulators of osteoclast formation RANKL [receptor activator of nuclear factor kappaB (RANK) ligand, osteoclast differentiation factor, TRANCE, osteoprotegerin ligand] and its natural inhibitor, osteoprotegerin (OPG), in the bone erosion of rheumatoid arthritis (RA).
Methods. mRNA was extracted from cells isolated from the pannus and synovial membrane regions of joints of 11 RA patients. Semiquantitative reverse transcription-polymerase chain reaction was carried out, and the isolated cells were also cultured to determine their ability to form osteoclasts.
Results. mRNAs encoding RANKL, RANK, OPG and macrophage-colony stimulating factor were expressed by cells isolated from RA joints. In addition, mRNA encoding for tumour necrosis factor apoptosis-inducing ligand and the osteoclast markers tartrate-resistant acid phosphatase and calcitonin receptor were also often expressed. Osteoclasts capable of forming resorption lacunae were generated from cells in the RA joints. At 50 ng/ml, recombinant OPG completely inhibited the resorptive activity of these cells. There was a significant correlation between the ratio of RANKL mRNA to OPG mRNA and the number of resorption pits produced (P = 0.028).
Conclusion. These data suggest that RANKL is an essential factor for osteoclast formation by cells in the rheumatic joint and that OPG may prevent the bone erosion seen in RA joints.

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Diverse Lewis acids and Brønsted acids were examined in the two-step, one-flask synthesis of meso-tetraphenylporphyrin, N-confused tetraphenylporphyrin, and tetraphenylsapphyrin. The scope of acid catalysis was found to be very broad, with 35 of 45 acids providing TPP in yields ranging from 5% to 58%. NC-TPP was also widely observed in yields of 1−40%, and TPS was infrequently observed in yields of &lt;1%. Additionally, conditions were found for direct preparation of magnesium TPP and copper TPP.

N-Confused meso-substituted porphyrin is a porphyrin isomer previously available from one-flask porphyrin syntheses as a low-yield byproduct (&lt;7.5%). We have found that methanesulfonic acid catalyzed condensation of pyrrole and benzaldehyde followed by DDQ oxidation provides N-confused tetraphenylporphyrin (NC-TPP) in up to 39% yield in analytical scale experiments. Preparative synthesis provided an isolated yield of 35% (800 mg). This represents a >5-fold yield improvement and makes significant quantities of NC-TPP readily available.

The fundamental physical and elcctrochromic properties of electrochemically produced poly(2',2''-bithiophene)-5',5''-diyl-1,4-phenylene (PDTB) have been studied. It has been found that a wide range of film morphology can be generated through variation of deposition conditions and cell electrolyte. Seven segment electrochromic displays utilising the material exhibit good colour contrast, and perfom well even after 103 cycles.

Abstract: We are beginning to understand the biological events that lead to aseptic loosening of total joint prostheses. Particles of wear, mostly liberated from the articulating surfaces of implants, are phagocytosed by macrophages and induce the release of inflammatory mediators (such as interleukin-1, tumour necrosis factor, interleukin-6 and prostaglandin E2) or cause cell death. These biological responses are thought to cause the bone loss that leads to prosthetic loosening. Drugs that suppress inflammatory mediators are successfully used to treat inflammatory diseases. Certain drugs can also reduce the corrosion of metal wear particles inside macrophages which enhances mediator release or cell death. Here we consider the prospect that these pharmacological treatments may enhance the long-term survival of implants.

Homeostatic regulation of cytoplasmic pH (pHeyt) against acid and alkaline challenges was studied in the human platelet using the intracellular indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Activation of a Na+/H+ exchanger in the plasma membrane is a known mechanism by which the platelet resists cytoplasmic acidification. The present study demonstrates an additional Na+-independent H extrusion mechanism which persists at low external Na+ concentration in the presence of 100 µM ouabain. This mechanism is inhibited by rotenone, oligomycin and an inhibitor of glycolysis, and is tentatively identified as a plasmalemmal H+-ATPase. The Na+-independent H extrusion mechanism partially restores cytoplasmic pH (pHeyt) after the cytoplasm is acidified by addition of 1 µM nigericin. The restoration process is energy-dependent and has a t1/2 of 7-21 min. The Na+-independent H+ extrusion mechanism is also shown capable of maintaining pHeyt ≊ 6.0 against an acidic pH, of 5.3 in an energy-dependent manner. The present study also revealed a Na+-independent, DIDS-inhibitable Cl-/HCO3- exchange activity. It removes alkaline equivalents from the cytoplasm with a half-time of 2.0 ± 0.4 min after alkaline loading with 25 mM NH4Cl. Its activity was also revealed in chloride to gluconate and gluconate to chloride perturbations of the external medium which raised or lowered pHeyt by 0.17 ± 0.05 or 0.14 ± 0.04 units, respectively. The activity of the anion exchanger allows the platelet to maintain pHext = 7.00 ± 0.11 at the alkaline pHext of 8.25. The combined activities of the Na+-independent H+ extrusion and Cl-/HCO3- exchange mechanisms make the platelet cytoplasm very resistant to changes in external pH. For variation of pHext between 5.0 and 8.5, pHeyt varies between 6.0 and 7.0, or roughly one-third as much.

The early changes in hepatic metallothionein (MT) and plasma zinc (Zn), copper (Cu), and iron (Fe) were investigated during the induction of adjuvant (AJ) arthritis in rats in conjunction with cyclosporin (CSA) treatment. Plasma Zn decreased after AJ injection (60% of control values at 8 h), and this was associated with a 4.5-fold increase in hepatic MT at 8 h. Plasma Zn was lowest at 16 h (40% of control), whereas hepatic MT concentrations increased to a maximum of 20-fold at 16 h. Changes in plasma Fe paralleled those of Zn, whereas plasma Cu levels were increased. Plasma metal and hepatic MT concentrations returned toward normal from d 1–7. At d 14, when marked paw swelling was apparent, hepatic MT and plasma Cu were again increased and plasma Zn decreased.

We have employed both small unilamellar vesicles (SUV) and large unilamellar vesicles formed by the reverse phase evaporation technique (REV) to study the initial kinetics of membrane aggregation and fusion. Stopped flow measurements of the calcium-induced changes in the turbidity of SUV and REV, formed from 1:1 (mol/mol) mixtures of bovine phosphatidylserine (PS) and Escherichia coli phosphatidylethanolamine (PE), were used to follow particle aggregation. Simultaneous measurements of the fluorescence resonance energy transfer from N-(7-nitro2,1,3-benzoxadiazol-4-yl) (NBD)-PE to rhodamine (Rho)-PE incorporated into the vesicle bilayers established that 1) both initial aggregation and fusion can be described as a bimolecular process and 2) the rate-limiting step of membrane fusion is aggregation. Thus fusion takes place in the microsecond time domain. Parallel experiments, which simultaneously measured aggregation and the dequenching of encapsulated carboxyfluorescein (CF) in the presence and absence of antifluorescein antibodies in the suspension medium, established that the small unilamellar vesicles rapidly lose their contents of CF as they fuse. On the other hand, the first few cycles of fusion of the large unilamellar vesicles are nonleaky, but leakage develops within 1-2 s as the particles grow in size. Thus the results demonstrate that the SUV are poor models for the study of nonleaky fusion, while the REV must be carefully tested before unambiguous interpretation of fusion assays involving the formation of tight complexes (such as the terbium-dipicolinic assay) can be made. NBD-PE undergoes very rapid, Ca2+-promoted changes in quantum yield which can obscure the resonance energy transfer signals. Thus data from the NBD-PE/Rho-PE energy transfer pair must be carefully scrutinized for artifacts.

This paper has examined the effect of within-stage mortality on the estimation of stage-specific survival rates bySouthwood's(1978, p. 358) method. As pointed out bySouthwood, both the severity and timing of mortality affect the mean duration of a life stage, and consequently the estimate of the number of individuals entering that stage. Knowledge of the form of the survivorship curve permits correction of the estimate under certain circumstances. The use ofSouthwood'smethod with two overlapping stages having different rates and patterns of mortality leads to complex errors in the estimation of survival for the first stage. The nature of these errors is examined analytically and via a simulation model.Southwood'smethod is fairly robust, with moderate differences in mortality rates leading to acceptable errors in estimating survival for the first stage. When both the rate and pattern of mortality in both life stages are the same, then the survival estimate is made without error. Precise estimates of stage-specific survival will not usually be possible withSouthwood'smethod because of the errors introduced by the very parameters being measured. Direct measurement of mortality rates and survivorship patterns (seeSouthwood, 1978, p. 309) is strongly advised, at least in preliminary work.

Chlorotetracycline (CTC) fluorescence is shown to be a competent and quantitative measure of the free internal calcium concentration, [Ca2+]i, obtained by ATP supported active uptake by bovine cardiac sarcolemmal (SL) vesicles. The fluorescence response of CTC to [Ca2+]i is calibrated by pre-equilibrating the vesicles with known Ca2+ concentrations and then diluting into a Ca2+-free medium containing CTC. The experiments show that CTC comes into equilibrium with the internal Ca2+ more rapidly than the latter can passively leak from the vesicles. The amplitude of the fluorescence increase is proportional to the Ca2+ concentration with which the vesicles are pre-equilibrated. This constitutes a calibration procedure for the use of CTC fluorescence as a quantitative measure of the free internal Ca2+ concentrations achieved in active transport. This method is applied to the determination of the average free Ca2+ concentrations achieved in ATP-energized uptake with sarcolemmal vesicles. Under optimal conditions an initial rate of 13 mM/min (37 nmol/mg/min) is observed. Uptake reaches a maximum corresponding to 70 mM (179 nmol/mg). Half-maximal values are obtained after 5 min of reaction. The mechanism of the CTC response to free internal Ca2+ concentration is discussed and is compared with measurements of vesicle-associated 45Ca2+.

Abstract: A simulation model is used to examine the errors in estimating parasitized and nonparasitized host densities independently with Southwood's graphical technique. This technique is accurate when parasitoid attack occurs prior to the sampling period (e.g. the previous life stage of the host). When this is not the case, the parasitized host density is estimated accurately, but the unparasitized host density is over estimated by those individuals that are sampled as healthy prior to attack. This error is neglible at low levels of parasitism (<20% parasitized), but increases with increasing parasitism. Of the biological parameters tested, only the parasitoid attack pattern (shape of the parasitoid attack curve) has a significant influence on the magnitude of this error. A generalized simulation model is presented for evaluating errors in estimates of seasonal parasitism for specific host-parasitoid interactions.