http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11500871
Angew Chem Int Ed Engl. 2001 Aug
3;40(15):2742-2781.
Real and Hypothetical Intermediate-Valence
Ag(II)/Ag(III) and Ag(II)/Ag(I) Fluoride Systems as Potential
Superconductors.
Grochala W, Hoffmann R.
Department of Chemistry and Chemical Biology and Cornell Center
for Materials Research Cornell University, Ithaca NY, 18453-1301
(USA).
With the aim of gauging their potential as conducting or superconducting
materials, we examine the crystal structures and magnetic properties
of the roughly one hundred binary, ternary, and quaternary Ag(II)
and Ag(III) fluorides in the solid state reported up to date.
The Ag(II) cation appears in these species usually in a distorted
octahedral environment, either in an [AgF](+) infinite chain
or as [AgF(2)] sheets. Sometimes one finds discrete square-planar
[AgF(4)](2-) ions. The Ag(III) cation occurs usually in the
form of isolated square-planar [AgF(4)](-) ions. Systems containing
Ag(III) (d(8)) centers are typically diamagnetic. On the other
hand, the rich spectrum of Ag(II) (d(9)) environments in binary
and ternary fluorides leads to most diverse magnetic properties,
ranging from paramagnetism, through temperature-independent
paramagnetism (characteristic for half-filled band and metallic
behavior) and antiferromagnetism, to weak ferromagnetism. Ag(II)
and Ag(III) have the same d-electron count as Cu(II) (d(9))
and Cu(III) (d(8)), respectively. F(-) and O(2-) ions are isoelectronic,
closed-shell (s(2)p(6)) species; both are weak-field ligands.
Led by these similarities, and by some experimental evidence,
we examine analogies between the superconducting cuprates (Cu(II)/Cu(III)-O(2-)
and Cu(II)/Cu(I)-O(2-) systems) and the formally mixed-valence
Ag(II)/Ag(III)-F(-) and Ag(II)/Ag(I)-F(-) phases. For this purpose
we perform electronic-structure computations for a number of
structurally characterized binary and ternary Ag(I), Ag(II),
and Ag(III) fluorides and compare the results with similar calculations
for oxocuprate superconductors. Electronic levels in the vicinity
of the Fermi level (x(2)-y(2) or z(2)) have usually strongly
mixed Ag(d)/F(p) character and are Ag-F antibonding, thus providing
the potential of efficient vibronic coupling (typical for d(9)
systems with substantially covalent bonds). According to our
computations this is the result not only of a coincidence in
orbital energies; surprisingly the Ag-F bonding is substantially
covalent in Ag(II) and Ag(III) fluorides. The electron density
of state at the Fermi level (DOS(F)) for silver fluoride materials
and frequencies of the metal-ligand stretching modes have values
close to those for copper oxides. The
above features suggest that properly hole- or electron-doped
Ag(II) fluorides might be good BCS-type superconductors.
We analyze a comproportionation/disproportionation equilibrium
in the hole-doped Ag(II) fluorides, and the possible appearance
of holes in the F(p) band. It seems that there is a chance of
generating an Ag(III)-F(-)/Ag(II)-F(0) "ionic/covalent"
curve crossing in the hole-doped Ag(II)-F(-) fluorides, significantly
increasing vibronic coupling.
PMID: 11500871 [PubMed - as supplied by publisher]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11540590
J Plant Physiol. 1998;152:315-22.
Ground-based studies with Super-Dwarf
wheat in preparation for space flight.
Salisbury FB, Gillespie LS, Campbell
WF, Hole P.
Plants, Soils, and Biometeorology Department, Utah State University,
Logan 84322-4820, USA.
Several experiments were carried out to test responses of a
Super-Dwarf cultivar of wheat (Triticum aestivum L.) to various
environmental parameters that were anticipated to be present
in our attempts to grow the wheat in a small growth chamber
on the Russian Space Station, Mir, or that proved to be present
in a 1995 trial space experiment. Under low photosynthetic photon
flux (40-400 micromoles m-2 s-1 PPF), development (e.g. anthesis)
was retarded, but heads (often sterile) always formed, even
if light was so low that plants died before the heads could
mature. Longer photoperiods promoted flowering, but night interruptions
combined with short days did not provoke a long-day response
as occurs with true long-day plants. The long-day effect could
prove to be a summation of photosynthetic products. Heat stress
(40 degrees C for 1-24 h) did not influence flowering but killed
plants that were 13-16-day-old (no effect on younger plants).
Concentrations of iodine or silver-fluoride disinfectants present
in the water used for plants on Mir (1.0-4.0 mg L-1) did not
affect plant growth although higher concentrations (8.0-1.6
mg L-1) were inhibitory. GA3 or indoleacetic acid applied
every other day at concentrations from 1.0 x 10(-6) mg L-1 to
3.162 x 10(-4) mg L-1 did not change the height of Super-Dwarf
wheat, suggesting that this cultivar is not a gibberellin mutant.
PMID: 11540590 [PubMed - indexed for MEDLINE]
From Toxline at Toxnet
Source: ROSSMOORE, H. W. (ED.). HANDBOOK OF BIOCIDE AND PRESERVATIVE
USE. XIV+424P. BLACKIE ACADEMIC AND PROFESSIONAL: GLASGOW, SCOTLAND,
UK; CHAPMAN AND HALL, INC.: NEW YORK, NEW YORK, USA. ISBN 0-7514-0212-5.;
0 (0). 1995. 83-132.
PAPER PULP AND FOOD GRADE PAPER
EAGON RG
BIOSIS COPYRIGHT: BIOL ABS. RRM BOOK CHAPTER BACTERIA YEAST
SLIME PAPER DAMAGE WHITE WATER REUSE CHEMICAL ADDITIVES BIOCIDE
USE
CAS Registry Numbers:
[too many to list, but includes]
7775-41-9
From Science Direct
Journal of Fluorine Chemistry; Volume 55, Issue 2 , 15 December 1991,
Pages 221-224
Some new chemistry of perfluoro-t-butylsilver
David I. Rossman, August J. Muller (1)
and Everett O. Lewis (2)
U.S. Army Chemical Research, Development
and Engineering Center, Aberdeen Proving Ground, MD 21010-5423
USA
1 First Chemical Corp, Pascagoula, MS 39581, USA.
2 Hoffman LaRoche, Nutley, NJ 07110,
USA.
Abstract. Perfluoro-t-butylsilver, prepared by the reaction
of silver fluoride with perfluoroisobutene,has been used to
prepare new perfluoro-t-butyl derivatives in good yield.
From Toxline at Toxnet
Arbete och Hälsa , 39 (Issue 1987:38 in Swedish) (1987)
pp 61-73
Scientific basis for Swedish Occupational
Standards. VIII. Consensus report for silver
Authors: Criteria group for occupational
standards
Abstract: The critical effect of occupational exposure to silver
and silver compounds is discoloration of tissues: argyria.
Keywords:
< ANIMAL >
< HUMAN >
toxicokinetics
occupational exposure
Skin
dose effect
CAS Registry Numbers:
563-63-3
7785-23-1
7775-41-9
7783-96-2
7783-90-6
80298-33-5
7761-88-8
20667-12-3
7440-22-4
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3485732&dopt=Abstract
Jpn
J Pharmacol 1986 Jan;40(1):191-3
Enhancement
of the twitch of bull frog sartorius muscle by fluorides.
Hattori T, Maehashi H.
Effects of 5 kinds of fluorides
on the twitch of the sartorius muscle of the bull frog were
investigated. All of the fluorides (0.1-2.0 mM) enhanced the
twitch evoked by nerve stimulation. The extents of enhancement
at 2.0 mM were in the order: stannous
fluoride much greater than potassium
fluoride greater than sodium silico
fluoride greater than sodium fluoride
greater than diammine silver fluoride.
The extent of each enhancement was larger than that in the case
of direct stimulation of the muscle. These findings show that
fluorides commonly enhance the
twitch of skeletal muscle and that the extent of enhancement
is related to the properties of cations included in the fluoride.
PMID: 3485732 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11062936&dopt=Abstract
Aust Dent
J 2000 Sep;45(3):187-92
Potential
of 4 per cent silver fluoride to
induce fluorosis in rats: clinical implications.
Gotjamanos T, Ma P.
Department of Pathology and School of Dentistry, University
of Western Australia.
The Health Department in Western Australia uses a 40 per cent
silver fluoride (AgF) solution for prevention and treatment
of dental caries in children. Analysis of this solution has
revealed high fluoride concentrations (75,000-120,000 mg/L),
raising concerns of potential toxicity and prompting investigation
of clinical protocols utilizing low-strength AgF in an animal
model. A single topical application of 4 per cent AgF solution
to Sprague-Dawley rats resulted in moderate to severe localized
fluorosis in 24 per cent of animals. In a second experiment,
caries was induced in rats aged 19 days; six weeks later, between
one-four carious molar teeth from each rat were treated with
4 per cent AgF (atraumatic technique). A generalized form of
fluorosis developed in the continually growing incisors of less
than 10 per cent of animals which had one or two carious teeth
treated, and in 70-90 per cent of rats which received AgF to
either three or four carious teeth. These results confirm the
potential of a 4 per cent AgF solution to induce fluorosis and
support previous recommendations that AgF at its empirical concentration
of 40 per cent should be withdrawn from clinical use.
PMID: 11062936 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9973713&dopt=Abstract
Aust Dent
J 1998 Dec;43(6):422-7
Abnormally
high fluoride levels in commercial preparations of 40 per cent
silver fluoride solution: contraindications
for use in children.
Gotjamanos T, Orton V.
Department of Pathology and School of Oral Health Sciences,
University of Western Australia.
Although a 40 per cent solution of silver
fluoride would be expected to contain 6 per cent fluoride (60,000
ppm), F-levels of 100,000 ppm and 120,000 ppm were found in
14 commercial samples analysed at The University of Western
Australia in 1993 and 1994. To determine whether F-levels in
40 per cent AgF preparations have remained high, the present
investigation was aimed at analysing different batches of commercial
preparations obtained more recently. Fluoride ion analysis was
carried out on 24 AgF samples using the Ion-Selective Electrode
technique. Independent analyses of the same samples were carried
out by a private chemical testing laboratory (Genalysis). Ten
samples supplied by Agson Chemical Export were found to contain
between 75,000 and 100,000 ppm F-: Genalysis reported 80,000
to 120,000 ppm. Fourteen samples supplied by Southern Dental
Industries were found to contain between 70,000 and 120,000
ppm F-; Genalysis reported 88,000 to 108,000 ppm F-. These results
confirm significantly higher than expected F-levels (ANOVA p
< 0.05) in commercial preparations of 40 per cent AgF. The
solutions tested were found to contain a mixture of ammonium
fluoride, sodium or potassium fluoride, and silver fluoride.
The additional presence of silver difluoride and hydrofluoric
acid resulting from the manufacturing process has been suggested
as an explanation for the much higher than expected levels of
fluoride ion. In view of possible toxicity
of 40 per cent AgF in young children, it is concluded that such
a highly concentrated solution should not be used clinically;
instead, lower strength AgF solutions should be investigated
for their efficacy in caries treatment.
PMID: 9973713 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9241926&dopt=Abstract
Aust Dent
J 1997 Jun;42(3):166-8
Safety
issues related to the use of silver fluoride
in paediatric dentistry.
Gotjamanos T.
School of Oral Health Sciences, Faculty of Medicine and Dentistry,
University of Western Australia.
Due to its exceedingly high fluoride content, 40% silver fluoride
solution has the potential to cause fluorosis when used in young
children. In vitro testing conducted in the present investigation
indicates that application of 40% silver fluoride to deep carious
lesions or its use as a 'spot' application agent could result
in 3 to 4 mg of fluoride reaching the systemic circulation.
As scientifically-based clinical trials on the safety of 40%
silver fluoride have not been conducted, it would be appropriate
for it to be withdrawn from further clinical use until proper
testing and evaluation have been carried out. In view of the
possibility that lower strength solutions of silver fluoride
(1-4%) may be just as effective as 40% in 'arresting' deep caries,
testing should focus on such solutions, particularly as the
potential for toxicity from their fluoride content would be
reduced by a factor of 10-40.
PMID: 9241926 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9078648&dopt=Abstract
Aust Dent
J 1997 Feb;42(1):52-3
Comment
in: Aust
Dent J. 1997 Aug;42(4):268-9.
Unacceptably
high levels of fluoride in commercial preparations of silver
fluoride.
Gotjamanos T, Afonso F.
Faculty of Medicine and Dentistry, University of Western Australia.
Instead of expected fluoride ion concentrations of around 60,000
ppm, commercial preparations of 40 per cent aqueous silver fluoride
were found to contain 120,000-127,000 ppm. Information received
from the Western Australian Chemistry Centre which provided
independent confirmation of the higher than expected [F] indicates
that the currently available commercial preparations contain
silver difluoride rather than silver fluoride. In view of the
potential of fluoride-containing products such as dentifrices
(1000-1500 ppm F) and topical fluoride gels and solutions (6000-12,000
ppm F) to cause adverse effects if excessive quantities are
ingested, any product that contains 120,000 ppm [F] should be
regarded as carrying a high risk of toxicity when used on young
children.
PMID: 9078648 [PubMed - indexed for MEDLINE]
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