High-pressure Debye-Waller and Grueneisen parameters of Au and Cu

The lattice vibrations are determined in the quasi-harmonic approximation for elemental Au and Cu to twice their normal density by first-principles electronic band-structure calculations. It is found for these materials that the important moments of the phonon density of states can be obtained to high accuracy from short-ranged force constant models. We discuss the implications for the Grueneisen parameters on the basis of calculated phonon moments and their approximations by using bulk moduli and Debye-Waller factors.Comment: 4 pages, 2 figures to appear in the proceedings of the 13th APS Topical Conference on Shock Compression of Condensed Matter (scheduled for April 2004

Finnsheep and their utilization in crosses with the Merino under range conditions of South-Africa

Two field trials were performed at two localities in a semiarid region to evaluate the performance of Finn (F) x Merino(M) crossbred females. The trials involved 781 F x M ewes and 657 M ewes. Ile de France, S.A. Mutton Merino, Dohne Merino, M, and F x M rams were used for matings. The F x M ewes were superior to M ewes in lambing-%, especially after mating as lambs, and the fecundities were 187and 107 %, resp. Multiple lambs of F x M ewes had better survival rates than those of M ewes. Lambs born from F x M ewes grew faster, had a larger weaning mass, over 10 % longer stables, ca. 2 mm thicker fibres, 30 % lower clean fleece weights, and a little less crimps/25 mm than those born from M ewes. Thus, F x M seemed to provide a suitable and acceptable composite showing remarkable adaptability to harsh environmental conditions. The results from the F x M wool and its special qualities can be regarded as useful attributes. Establishment of a composite F x M female line appeared well-founded

Genetic and phenotypic parameters of pelt traits in a Karakul control flock

Genetic parameters of 16 pelt trais and birth mass were calculated in a Karakul control flock (n =2058; rams= 305) with a half-sib analysis. Moderately high heritabilities were estimated for pelt traits. No antagonistic genetic correlation was found between pattern and hair quality. The genetic correlations between pattern and pelt traits were lower than those estimated for hair quality and the other pelt traits. The expected correlated response from selection for hair quality may be a decrease in the occurrence of brittle hair, hair thickness, metallic, skin thickness, occurence of feathers, hair stiffness and an increase in hair length, lustre and curl breadth. Selection for pattern may result in a decrease in bandedness, a slight increase in lustre and in the occurrence of feathers, and a moderate decrease in curl type and hair length. Genetic estimates obtained in this study are compared with previous estimates obtained in Karakul sheep. Genetiese parameters van 16 pelseienskappe en van geboortemassa is in 'n Karakoelkontrole-kudde( n =2058; ramme = 305) met behulp van die halfsib-metodeb eraam. Matige hoe oorerflikhede is vir pelseienskappe beraam. Geen antagonistiese genetiese korrelasie is tussen patroon en haarkwaliteit gevind nie. Die genetiese korrelasies tussen patroon en ander pelseienskappe was heelwat laer as die tussen haarkwaliteit en die ander pelseienskappe. Die verwagte gekorreleerde responsie van seleksie vir haarkwaliteit mag 'n afname in die voorkoms van breekhare, haardikte, metaalagtigheid, veldikte, voorkoms van vere, haarstyfte, en 'n toename in haarlengte, glans en krulgrootte wees. Seleksie vir patroon mag 'n afname in die voorkoms van bande, 'n effense toename in glans en in die voorkoms van vere en 'n matige afname in krultipe en haarlengte veroorsaak. Genetiese parameters verkry in hierdie studie word met ander studiesb y Karakoelskape vergelyk.Keywords: Karakul, pelt traits, genetic and phenotypic parameters

Phase Transitions in High Purity Zr Under Dynamic Compression

We present results from ramp compression experiments on high-purity Zr that show the $\alpha \rightarrow \omega$, $\omega \rightarrow \beta$, as well as reverse $\beta \rightarrow \omega$ phase transitions. Simulations with a multi-phase equation of state and phenomenological kinetic model match the experimental wave profiles well. While the dynamic $\alpha \rightarrow \omega$ transition occurs $\sim 9$ GPa above the equilibrium phase boundary, the $\omega \rightarrow \beta$ transition occurs within 0.9~GPa of equilibrium. We estimate that the dynamic compression path intersects the equilibrium $\omega - \beta$ line at $P= 29.2$ GPa, and $T = 490$ K. The thermodynamic path in the interior of the sample lies $\sim 100$ K above the isentrope at the point of the $\omega \rightarrow \beta$ transition. Approximately half of this dissipative temperature rise is due to plastic work, and half is due to the non-equilibrium $\alpha \rightarrow \omega$ transition. The inferred rate of the $\alpha \rightarrow \omega$ transition is several orders of magnitude higher than that measured in dynamic diamond anvil cell (DDAC) experiments in an overlapping pressure range. We discuss a model for the influence of shear stress on the nucleation rate. The small fractional volume change $\Delta V/V \approx 0.1$ at the $\alpha \rightarrow \omega$ transition amplifies the effect of shear stress, and we estimate that for this case shear stress is equivalent to a pressure increase in the range of several GPa. Correcting our transition rate to a hydrostatic rate brings it approximately into line with the DDAC results, suggesting that shear stress plays a significant role in the transformation rate

Electron correlation in C_(4N+2) carbon rings: aromatic vs. dimerized structures

The electronic structure of C_(4N+2) carbon rings exhibits competing many-body effects of Huckel aromaticity, second-order Jahn-Teller and Peierls instability at large sizes. This leads to possible ground state structures with aromatic, bond angle or bond length alternated geometry. Highly accurate quantum Monte Carlo results indicate the existence of a crossover between C_10 and C_14 from bond angle to bond length alternation. The aromatic isomer is always a transition state. The driving mechanism is the second-order Jahn-Teller effect which keeps the gap open at all sizes.Comment: Submitted for publication: 4 pages, 3 figures. Corrected figure

Underreporting of meningococcal disease incidence in the Netherlands: results from a capture-recapture analysis based on three registration sources with correction for false positive diagnoses.

In order to come to a reliable evaluation of the effectiveness of the chosen vaccination policy regarding meningococcal disease, the completeness of registrations on meningococcal disease in the Netherlands was estimated with the capture-recapture method. Data over 1993-1998 were collected from (A) mandatory notifications (n = 2926); (B) hospital registration (n = 3968); (C) laboratory surveillance (n = 3484). As the standard capture-recapture method does not take into account false positive diagnoses, we developed a model to adjust for the lack of specificity of our sources. We estimated that 1363 cases were not registered in any of the three sources in the period of study. The completeness of the three sources was therefore estimated at 49% for source A, 67% for source B and 58% for source C. After adjustment for false positive diagnoses, the completeness of source A, B, and C was estimated as 52%, 70% and 62%, respectively. The capture-recapture methods offer an attractive approach to estimate the completeness of surveillance sources and hence contribute to a more accurate estimate of the disease burden under study. However, the method does not account for higher-order interactions or presence of false positive diagnoses. Being aware of these limitations, the capture-recapture method still elucidates the (in)completeness of sources and gives a rough estimate of this (in)completeness. This makes a more accurate monitoring of disease incidence possible and hence attributes to a more reliable foundation for the design and evaluation of health interventions such as vaccination programs

Few figs for frugivores: Riparian fig trees in Zimbabwe may not be a dry season keystone resource

Most plants flower and fruit at times of year when probabilities of pollination and seedling establishment are high. Fig trees (Ficus spp.) are often considered as keystone resources for vertebrate frugivores, in part because of year‐round fig production. This unusual fruiting phenology results in the maintenance of fig wasp populations, but in seasonal environments this means fruiting occurs during periods when the chances of seedling establishment are low. Under these circumstances, selection is expected to favour any individuals that reduce or eliminate fruiting at these times. Here, we describe a large‐scale survey of the extent of dry season fruiting by three riparian Ficus species in Gonarezhou National Park, Zimbabwe. Few trees of two monoecious species, F. sycomorus and F. abutilifolia, had figs, and most crops of F. sycomorus were far smaller than the trees were capable of producing. Large stands of the dioecious F. capreifolia were present, but fig densities were low and no mature female (seed containing) figs were recorded. Even though fig trees may have been the only species bearing fruit, the consequences of the low investment in reproduction by the three Ficus species were clear—there were too few figs for a landscape‐scale keystone role

Patterns of African and Asian admixture in the Afrikaner population of South Africa

Abstract: Background: The Afrikaner population of South Africa is the descendants of European colonists who started to colonize the Cape of Good Hope in the 1600s. In the early days of the colony, mixed unions between European males and non-European females gave rise to admixed children who later became incorporated into either the Afrikaner or the Coloured populations of South Africa. Differences in ancestry, social class, culture, sex ratio and geographic structure led to distinct and characteristic admixture patterns in the Afrikaner and Coloured populations. The Afrikaner population has a predominant European composition, whereas the Coloured population has more diverse ancestries. Genealogical records previously estimated the contribution of non-Europeans into the Afrikaners to be between 5.5 and 7.2%. Results: To investigate the genetic ancestry of the Afrikaner population today (11–13 generations after initial colonization), we genotyped approximately five million genome-wide markers in 77 Afrikaner individuals and compared their genotypes to populations across the world to determine parental source populations and admixture proportions. We found that the majority of Afrikaner ancestry (average 95.3%) came from European populations (specifically northwestern European populations), but that almost all Afrikaners had admixture from non-Europeans. The non-European admixture originated mostly from people who were brought to South Africa as slaves and, to a lesser extent, from local Khoe-San groups. Furthermore, despite a potentially small founding population, there is no sign of a recent bottleneck in the Afrikaner compared to other European populations. Admixture amongst diverse groups from Europe and elsewhere during early colonial times might have counterbalanced the effects of a small founding population. Conclusions: While Afrikaners have an ancestry predominantly from northwestern Europe, non-European admixture signals are ubiquitous in the Afrikaner population. Interesting patterns and similarities could be observed between genealogical predictions and our genetic inferences. Afrikaners today have comparable inbreeding levels to currentday European populations

Successful control of a hospital-wide outbreak of OXA-48 producing Enterobacteriaceae in the Netherlands, 2009 to 2011

On 31 May 2011, after notification of Klebsiella pneumoniae(KP)(OXA-48);(CTX-M-15) in two patients, nosocomial transmission was suspected in a Dutch hospital. Hospital-wide infection control measures and an outbreak investigation were initiated. A total of 72,147 patients were categorised into groups based on risk of OXA-48 colonisation or infection, and 7,527 were screened for Enterobacteriaceae(OXA-48) by polymerase chain reaction (PCR). Stored KP isolates (n=408) were retrospectively tested for OXA-48 and CTX-M-1 group extended-spectrum beta-lactamases (ESBL). 285 KP isolates from retrospective and prospective patient screening were genotyped by amplified fragment length polymorphism (AFLP). 41 isolates harbouring different Enterobacteriaceae species were analysed by plasmid multilocus sequence typing (pMLST). No nosocomial transmission of Enterobacteriaceae(OXA-48) was detected after 18 July 2011. Enterobacteriaceae(OXA-48) were found in 118 patients (KP (n=99), Escherichia coli (n=56), >= 1 Enterobacteriaceae(OXA-48) species (n=52)),of whom 21 had clinical infections. 39/41 (95%) of OXA-48 containing plasmids were identical in pMLST. Minimum inhibitory concentrations (MICs) of KPOXA-48 and E. coli(OXA-48) for imipenem and meropenem ranged from = 16 mg/L, and 153/157 (97%) had MIC >0.25mg/L for ertapenem. AFLP identified a cluster of 203 genetically linked isolates (62 KPOXA-48;(CTX-M15); 107 KPCTX-M-15; 34 KPOXA-48). The 'oldest' KPCTX-M-15 and KPOXA-48 clonal types originated from February 2009 and September 2010, respectively. The last presumed outbreak-related KPOXA-48 was detected in April 2012. Uncontrolled transmission of KP (CTX-M-15) evolved into a nosocomial outbreak of KPOXA-48; CTX-M15 with large phenotypical heterogeneity. Although the outbreak was successfully controlled, the contribution of individual containment measures and of the hospital relocating into a new building just before outbreak notification was impossible to quantify

Update on Streptococcus suis research and prevention in the era of antimicrobial restriction: 4th International Workshop on S. suis

Streptococcus suis is a swine pathogen and a zoonotic agent afflicting people in close contact with infected pigs or pork meat. Sporadic cases of human infections have been reported worldwide. In addition, S. suis outbreaks emerged in Asia, making this bacterium a primary health concern in this part of the globe. In pigs, S. suis disease results in decreased performance and increased mortality, which have a significant economic impact on swine production worldwide. Facing the new regulations in preventive use of antimicrobials in livestock and lack of effective vaccines, control of S. suis infections is worrisome. Increasing and sharing of knowledge on this pathogen is of utmost importance. As such, the pathogenesis and epidemiology of the infection, antimicrobial resistance, progress on diagnosis, prevention, and control were among the topics discussed during the 4th International Workshop on Streptococcus suis (held in Montreal, Canada, June 2019). This review gathers together recent findings on this important pathogen from lectures performed by lead researchers from several countries including Australia, Canada, France, Germany, Japan, Spain, Thailand, The Netherlands, UK, and USA. Finally, policies and recommendations for the manufacture, quality control, and use of inactivated autogenous vaccines are addressed to advance this important field in veterinary medicine