1,372 research outputs found
Observation of Buried Phosphorus Dopants near Clean Si(100)-(2x1) with Scanning Tunneling Microscopy
We have used scanning tunneling microscopy to identify individual phosphorus
dopant atoms near the clean silicon (100)-(2x1) reconstructed surface. The
charge-induced band bending signature associated with the dopants shows up as
an enhancement in both filled and empty states and is consistent with the
appearance of n-type dopants on compound semiconductor surfaces and passivated
Si(100)-(2x1). We observe dopants at different depths and see a strong
dependence of the signature on the magnitude of the sample voltage. Our results
suggest that, on this clean surface, the antibonding surface state band acts as
an extension of the bulk conduction band into the gap. The positively charged
dimer vacancies that have been observed previously appear as depressions in the
filled states, as opposed to enhancements, because they disrupt these surface
bands.Comment: 4 pages, 3 figures. TeX for OSX from Wierde
The potential and pitfalls of using simple dental metrics to infer the diets of African antelopes (Mammalia: Bovidae)
The use of mesowear to infer diets of extinct species is fast becoming widespread in palaeoecological studies. Nevertheless, traditional mesowear analyses suffer from a specimen number limitation, in that a minimum number of specimens identified to the species level is necessary to make accurate dietary predictions. This is problematic in many fossil African antelope (Mammalia: Bovidae) assemblages, where isolated teeth cannot always be assigned to species. Hereweexplore the possibility of using simple dental metrics to predict diets on the basis of individual teeth as well as gnathic rows using linear discriminant function analyses.We find that browsers are accurately classified at both the individual and species levels, across all models and tooth positions. Mixed feeders and grazers are classified accurately only sometimes, and this is probably a reflection of the more limited sample size of larger bodied species in our study. Body size was a highly significant predictor of the inaccurate classifications obtained in our models, with larger bodied species tending to grazing classifications and smaller bodied species browsing classifications. Nevertheless, the models correctly classify the majority of specimens we examined to their correct trophic group, as determined through stable isotope analyses or as defined through the literature. The methods outlined hold some promise for determining the diets of isolated fossil specimens unassigned to species in a simple manner and, when used in conjunction with other palaeodietary and palaeoecological proxies, may help determine palaeoenvironments more accurately
The significance of 'the visit' in an English category-B prison: Views from prisoners, prisoners' families and prison staff
A number of claims have been made regarding the importance of prisoners staying in touch with their family through prison visits, firstly from a humanitarian perspective of enabling family members to see each other, but also regarding the impact of maintaining family ties for successful rehabilitation, reintegration into society and reduced re-offending. This growing evidence base has resulted in increased support by the Prison Service for encouraging the family unit to remain intact during a prisoner’s incarceration. Despite its importance however, there has been a distinct lack of research examining the dynamics of families visiting relatives in prison. This paper explores perceptions of the same event – the visit – from the families’, prisoners’ and prison staffs' viewpoints in a category-B local prison in England. Qualitative data was collected with 30 prisoners’ families, 16 prisoners and 14 prison staff, as part of a broader evaluation of the visitors’ centre. The findings suggest that the three parties frame their perspective of visiting very differently. Prisoners’ families often see visits as an emotional minefield fraught with practical difficulties. Prisoners can view the visit as the highlight of their time in prison and often have many complaints about how visits are handled. Finally, prison staff see visits as potential security breaches and a major organisational operation. The paper addresses the current gap in our understanding of the prison visit and has implications for the Prison Service and wider social policy
The use of PCR-RFLP as an identification tool for two closely related species of bats of genus Platyrrhinus
Excited States of Ladder-type Poly-p-phenylene Oligomers
Ground state properties and excited states of ladder-type paraphenylene
oligomers are calculated applying semiempirical methods for up to eleven
phenylene rings. The results are in qualitative agreement with experimental
data. A new scheme to interpret the excited states is developed which reveals
the excitonic nature of the excited states. The electron-hole pair of the
S1-state has a mean distance of approximately 4 Angstroem.Comment: 24 pages, 21 figure
Resonant X-ray emission spectroscopy reveals d–d ligand-field states involved in the self-assembly of a square-planar platinum complex
Resonant X-ray Emission Spectroscopy (RXES) is used to characterize the ligand field states of the prototypic self-assembled square-planar complex, [Pt(tpy)Cl]Cl (tpy=2,2′:6′,2′′-terpyridine), and determine the effect of weak metal-metal and π-π interactions on their energy. © 2012 the Owner Societies
Mr imaging findings of lesions involving cartilage and bone in the paediatric knee: a pictorial review
The knee is the joint which is most commonly imaged by MRI in children and adolescents. With increasing participation in competitive sports, traumatic knee injuries with osteochondral lesions are increasingly common in children. However, it is also important to exclude non traumatic conditions that result in defects of the articular cartilage and/or subchondral bone plate or growth plate of the knee, since timely diagnosis and therapy may help prevent lifelong disability in these patients. Moreover, there are normal variants that occur in the ossifying knee that should not be mistaken for lesions. The aim of this essay is to review the wide range of conditions that may result in MRI signal changes of the ossifying knee in children
Mr imaging findings of lesions involving cartilage and bone in the paediatric knee: a pictorial review
The knee is the joint which is most commonly imaged by MRI in children and adolescents. With increasing participation in competitive sports, traumatic knee injuries with osteochondral lesions are increasingly common in children. However, it is also important to exclude non traumatic conditions that result in defects of the articular cartilage and/or subchondral bone plate or growth plate of the knee, since timely diagnosis and therapy may help prevent lifelong disability in these patients. Moreover, there are normal variants that occur in the ossifying knee that should not be mistaken for lesions. The aim of this essay is to review the wide range of conditions that may result in MRI signal changes of the ossifying knee in children
Weak ferromagnetism with very large canting in a chiral lattice: (pyrimidine)2FeCl2
The transition metal coordination compound (pyrimidine)2FeCl2 crystallizes in
a chiral lattice, space group I 4_1 2 2 (or I4_3 2 2). Combined magnetization,
Mossbauer spectroscopy and powder neutron diffraction studies reveal that it is
a canted antiferromagnet below T_N = 6.4 K with an unusually large canting of
the magnetic moments of 14 deg. from their general antiferromagnetic alignment,
one of the largest reported to date. This results in weak ferromagnetism with a
ferromagnetic component of 1 mu_B. The large canting is due to the interplay
between the antiferromagnetic exchange interaction and the local single-ion
anisotropy in the chiral lattice. The magnetically ordered structure of
(pyrimidine)2FeCl2, however, is not chiral. The implications of these findings
for the search of molecule based materials exhibiting chiral magnetic ordering
is discussed.Comment: 6 pages, 5 figure
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