162 research outputs found
Hibbertia subvillosa (Dilleniaceae), a new Western Australian species segregated from H. striata
The south-west Western Australian species Hibbertia striata (Steud.) K.R.Thiele was reinstated in 2017, segregated from the historically misunderstood H. huegelii (Endl.) F.Muell. Since that time, field work has shown that H. striata comprises two distinctly different morphotypes. Plants from the eastern (drier) edge of the range are consistently single-stemmed at the base and are obligate reseeders after fire and other disturbances, in contrast to a more widespread morphotype (which includes the type of H. striata), that is abundantly multi-stemmed from the base and is a resprouter after fire. The difference in habit is consistent, has been observed at multiple locations and is consistently associated with distinct (though subtle) differences in leaf indumentum and morphology. The two morphotypes have not been found growing in mixed populations, due to habitat differences. Field work has shown that they are narrowly sympatric and do not intergrade where they approach each other; for this reason, and the consistency of both morphotypes over a wide range, they are regarded here as distinct species. The reseeding taxon has a validly published name, H. huegelii (Endl.) F.Muell. var. subvillosa Domin, and this is raised here to species rank as Hibbertia subvillosa (Domin) K.R.Thiele & T.Hammer.K.R. Thiele, T.A. Hamme
Hibbertia glaucophylla is the correct name for the Western Australian species currently known as H. rupicola (Dilleniaceae)
There has been historical confusion and error in the application and typification of the name Pleurandra glaucophylla Steud., likely caused by a slip of the pen on the original collecting label which caused the collecting number assigned by Preiss (2179) to be mis-transcribed as 2159, a number already used for another Preiss collection. We show that the type of P. glaucophylla falls within the circumscription of the species currently known as Hibbertia rupicola (S.Moore) C.A.Gardner, necessitating the new combination H. glaucophylla (Steud.) K.R.Thiele & T.Hammer as the correct name for the species currently known as H. rupicola.K.R. Thiele & T.A. Hamme
Impact of super absorbent polymers on early age behavior of ultra-high performance concrete walls
Early age cracking, a common problem for Ultra-High Performance Concrete (UHPC), is caused by Autogenous Shrinkage (AS) and self-desiccation arising from the chemical shrinkage during the cement hydration reactions when the deformation is restrained. However, to avoid the crack development initiated by AS, several solutions can be adopted; one example is the addition of a promising material, considered as an internal curing agent, the Super Absorbent Polymers (SAP) which limits the capillary depressions that can enhance the formation of the crack. In this study the main goal is to mitigate the shrinkage using SAPs in infrastructure under severe conditions. Therefore, a demonstrator wall was built simulating a typical case with high risk of cracking. With the help of fiber optic SOFO sensors embedded in the wall, real-time deformations are recorded and compared the demountable mechanical strain gauges (DEMEC) measurements to further investigate the behavior of SAPs in real scale infrastructure. The amount of extra water (in SAP) needed to mitigate shrinkage was determined by performing chemical shrinkage tests on different cement paste combinations. Tests of autogenous shrinkage were performed on mortars using corrugated tubes and showed that SAPs reduce to some extent the AS. Under restrained conditions via ring tests, SAP specimens did not crack. Therefore, SAPs were found promising towards mitigating the shrinkage and enhancing the early age behavior of concrete for a better durability
Hibbertia advena (Dilleniaceae), a new and rare species from Queensland with transcontinental affinities
The new species Hibbertia advena T.Hammer & Toelken is described. It occurs in north-east Queensland but shares a strong morphological affinity with members of the H. exasperata (Steud.) Briq. species group, which are widespread in south-west Western Australia. This may be an example of a very wide transcontinental disjunction in Australian Hibbertia. The biogeographic significance of such disjunctions is briefly discussed, pending further insights when a more complete molecular phylogeny of the genus is generated.T.A. Hammer, H.R. Toelken, K.R. Thiel
The hyperon-nucleon interaction: conventional versus effective field theory approach
Hyperon-nucleon interactions are presented that are derived either in the
conventional meson-exchange picture or within leading order chiral effective
field theory. The chiral potential consists of one-pseudoscalar-meson exchanges
and non-derivative four-baryon contact terms. With regard to meson-exchange
hyperon-nucleon models we focus on the new potential of the Juelich group,
whose most salient feature is that the contributions in the scalar--isoscalar
(\sigma) and vector--isovector (\rho) exchange channels are constrained by a
microscopic model of correlated \pi\pi and KKbar exchange.Comment: 28 pages, 8 figures, submitted to Lecture Notes in Physic
Charmless Three-Body Baryonic B Decays
Motivated by recent data on B-> p pbar K decay, we study various charmless
three-body baryonic B decay modes, including Lambda pbar pi, Sigma0 pbar pi, p
pbar pi, p pbar Kbar0, in a factorization approach. These modes have rates of
order 10^{-6}. There are two mechanisms for the baryon pair production,
current-produced and transition. The behavior of decay spectra from these
baryon production mechanisms can be understood by using QCD counting rules.
Predictions on rates and decay spectra can be checked in the near future.Comment: 26 pages, 9 figures; version to appear in Phys. Rev.
Surgery for degenerative cervical myelopathy: a nationwide registry-based observational study with patient-reported outcomes
BACKGROUND: Indications and optimal timing for surgical treatment of degenerative cervical myelopathy (DCM) remain unclear, and data from daily clinical practice are warranted.OBJECTIVE: To investigate clinical outcomes following decompressive surgery for DCM.METHODS: Data were obtained from the Norwegian Registry for Spine Surgery. The primary outcome was change in the neck disability index (NDI) 1 yr after surgery. Secondary endpoints were the European myelopathy score (EMS), quality of life (EuroQoL 5D [EQ-5D]), numeric rating scales (NRS) for headache, neck pain, and arm pain, complications, and perceived benefit of surgery assessed by the Global Perceived Effect (GPE) scale.RESULTS: We included 905 patients operated between January 2012 and June 2018. There were significant improvements in all patient-reported outcome measures (PROMs) including NDI (mean -10.0, 95% CI -11.5 to -8.4, P<.001), EMS (mean 1.0, 95% CI 0.8-1.1, P<.001), EQ-5D index score (mean 0.16, 95% CI 0.13-0.19, P<.001), EQ-5D visual analogue scale (mean 13.8, 95% CI 11.7-15.9, P<.001), headache NRS (mean -1.1, 95% CI -1.4 to -0.8, P<.001), neck pain NRS (mean-1.8, 95% CI-2.0 to-1.5, P<.001), and arm pain NRS (mean -1.7, 95% CI -1.9 to -1.4, P<.001). According to GPE scale assessments, 229/513 patients (44.6%) experienced "complete recovery" or felt "much better" at 1 yr. There were significant improvements in all PROMs for both mild and moderate-to-severe DCM. A total of 251 patients (27.7%) experienced adverse effects within 3 mo.CONCLUSION: Surgery for DCM is associated with significant and clinically meaningful improvement across a wide range of PROMs.Scientific Assessment and Innovation in Neurosurgical Treatment Strategie
Alpha scattering and capture reactions in the A = 7 system at low energies
Differential cross sections for He- scattering were measured in
the energy range up to 3 MeV. These data together with other available
experimental results for He and H scattering were
analyzed in the framework of the optical model using double-folded potentials.
The optical potentials obtained were used to calculate the astrophysical
S-factors of the capture reactions HeBe and
HLi, and the branching ratios for the transitions into
the two final Be and Li bound states, respectively. For
HeBe excellent agreement between calculated and
experimental data is obtained. For HLi a value
has been found which is a factor of about 1.5 larger than the adopted value.
For both capture reactions a similar branching ratio of has been obtained.Comment: submitted to Phys.Rev.C, 34 pages, figures available from one of the
authors, LaTeX with RevTeX, IK-TUW-Preprint 930540
Study of hybrid Х pinches in different conditions
A standard X-pinch consists of two or more fine wires that cross at a single point as the load of a pulsed power generator. To simplify the X-pinch load, a hybrid configuration consisting of solid conical electrodes connected by a wire, has been suggested and tested on four generators ranging in current from 200 kA to 1 MA and risetimes varying from 45 to 170 ns. The experiments have shown that for each generator, a wire material, diameter and length can be found for which the X-pinches generate a single intense burst of soft x-rays and develop a single hot spot. Also they generated less hard x-ray intensity than that measured in comparable standard X-pinches.Стандартные Х-пинчи состоят из двух или более проволочек, перекрещенных в диоде сильноточного генератора. Чтобы упростить конфигурацию Х-пинчей, была предложена и протестирована на четырех сильноточных генераторах с токами от 200 кА до 1 МА и временем нарастания импульса от 45 до 170 нс нагрузка в виде гибридного Х-пинча. Гибридные Х-пинчи состоят из двух твердотельных тугоплавких электродов, соединенных проволочкой. Проведенные эксперименты показали, что для каждого генератора можно подобрать материал проволочки, диаметр и длину, при которых гибридные Х-пинчи образуют единичную горячую точку и излучают интенсивную вспышку мягкого рентгеновского излучения. При этом зарегистрированный уровень жесткого рентгеновского излучения был значительно ниже, чем в стандартных Х-пинчах.Стандартні Х-пінчі складаються з двох або більше дротиків, перехрещених у діоді потужнострумового генератора. Щоб спростити конфігурацію Х-пінча, була запропонована і протестована на чотирьох потужнострумових генераторах із струмами від 200 кА до 1 МА та часом наростання імпульсу від 45 до 170 нс навантаження у вигляді гібридного Х-пінча. Гібридні Х-пінчі складаються з двох твердотільних тугоплавких електродів, з'єднаних дротиком. Проведені експерименти показали, що для кожного генератора можна підібрати матеріал дротика, діаметр і довжину, при яких гібридні Х-пінчі утворюють одиничну гарячу краплю та випромінюють інтенсивний спалах м'якого рентгенівського випромінювання. При цьому зареєстрований рівень жорсткого рентгенівського випромінювання був значно нижче, ніж у стандартних Х-пінчах
Genetic signatures of parental contribution in black and white populations in Brazil
Two hundred and three individuals classified as white were tested for 11 single nucleotide polymorphisms plus two insertion/deletions in their Y-chromosomes. A subset of these individuals (n = 172) was also screened for sequences in the first hypervariable segment of their mitochondrial DNA (mtDNA). In addition, complementary studies were done for 11 of the 13 markers indicated above in 54 of 107 black subjects previously investigated in this southern Brazilian population. The prevalence of Y-chromosome haplogroups among whites was similar to that found in the Azores (Portugal) or Spain, but not to that of other European countries. About half of the European or African mtDNA haplogroups of these individuals were related to their places of origin, but not their Amerindian counterparts. Persons classified in these two categories of skin color and related morphological traits showed distinct genomic ancestries through the country. These findings emphasize the need to consider in Brazil, despite some general trends, a notable heterogeneity in the pattern of admixture dynamics within and between populations/groups
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