Gas-phase Crystallization of Titanium Dioxide Nanoparticles

We have investigated the development of crystal morphology and phase in ultrafine titanium dioxide particles. The particles were produced by a droplet-to-particle method starting from propanolic titanium tetraisopropoxide solution, and calcined in a vertical aerosol reactor in air. Mobility size classified 40-nm diameter particles were conveyed to the aerosol reactor to investigate particle size changes at 20–1200°C with 5–1-s residence time. In addition, polydisperse particles were used to study morphology and phase formation by electron microscopy. According to differential mobility analysis, the particle diameter was reduced to 21–23-nm at 600°C and above. Precursor decomposition occurred between 20°C and 500°C. The increased mobility particle size at 700°C and above was observed to coincide with irregular particles at 700°C and 800°C and faceted particles between 900°C and 1200°C, according to transmission electron microscopy. The faceted anatase particles were observed to approach a minimized surface energy by forming {101} and {001} crystallographic surfaces. Anatase phase was observed at 500–1200°C and above 600°C the particles were single crystals. Indications of minor rutile formation were observed at 1200°C. The relatively stable anatase phase vs. temperature is attributed to the defect free structure of the observed particles and a lack of crystal–crystal attachment points.     

A search for the S(1936) in 100 GeV pBe interactions

A search for the S(1936) has been made in the invariant mass spectrum of p?p-pairs produced inclusively in proton-beryllium interactions at 100 GeV incident momentum. No enhancement is observed, giving a 3 standard deviation upper limit on the cross section of 220 nb/nucleon for production of a narrow p?p state around ≈ 1940 MeV in the x_F range 0.18 <x_F<0.48.     

High statistics inclusive ϕ meson production at SPS energies

Inclusive ? meson production has been measured for 100 GeV/c and 200 GeV/c incident π^?, \(\bar p\) andK ^?, and for 120 GeV/c and 200 GeV/c incident π⁺,p andK ⁺, using a Be target. A total of 630,000 ? mesons has been recorded in the kinematic range 0<x _F <0.4. Presented are the differential cross sectionsdσ/dx _F anddσ/dp _T ². The longitudinal momentum distributions show that the strange valence quarks of the incidentK mesons play an important role in ? meson production, even at smallx _F . The decay angular distribution of the ? meson is evaluated in the Gottfried-Jackson frame and is expressed in the elements of the density matrix. There is a small but significant cos² θ _GJ dependence for smallp _T , which decreases for increasingp _T .     

Inclusive ϕ meson production,the parton fusion model and strange quark structure functions

The parton fusion model is used to describe the longitudinal differential cross section (dσ/dx _F ) of hadronic ? production. Thedσ/dx _F for ? production in π^± p, \(\mathop p\limits^{( - )} p\) andK ^± p interactions is evaluated in the model by using structure functions for the constituents of the interacting particles. A comparison between the model and high statistics data in the Feynmanx range 0.0<x _F (?)<0.4 allows the determination of the strange valence quark distribution inK mesons and the strange sea quark distribution in π mesons, which appears to be harder than the light sea quark distribution. The comparison also shows that a significant part of inclusive ? production is due to the OZI allowed fusion of strange quarks, while the OZI inhibited fusion diagrams are strongly suppressed.     

Inclusive Λ(1,520) production in 100 GeVp Be interactions

The reactionpBe→Λ(1,520)X has been measured at 100 GeV incident momentum in the kinematic range 0.15<x<0.35 \((x = 2p_\parallel ^{c.m} /\sqrt s )\) andP _T <1 GeV. The invariant cross section is compatible with that measured forpp interactions at the CERN-ISR. The differential cross sectiondσ/dp _T ² is fitted to an exponentiale ^?αp _T ² with α=2.7 GeV^?2.     

Zur Chemie des Kanemits [NaHSi2O5 · 3 H2O]x

On the Chemistry of Kanemite [NaHSi₂O₅ · 3 H₂O]_x Starting from δ-Na₂Si₂O₅ Kanemit was prepared by a direct exchange of Na⁺ by H⁺ in water containing reaction mixtures. By ²⁹Si-, ²³Na- and ¹H-MAS-NMR investigations Kanemit was characterized as a layersilicate [NaHSi₂O₅ · 3 H₂O]. By thermal treatment as well as by dehydration at room temperature under vacuum conditions a monohydrate is formed in which the layerstructure remains nearly unchanged. At temperatures between 100 and 110°C under normal conditions a hydrate phase of the composition [NaHSi₂O₅ · 0.25 H₂O]_x is prepared in which a changed silicate-layerstructure exists.     

Reactions at the Boron‐Carbon Double Bond of Methyl(methylidene)boranes

The addition of Lewis bases L to the methyl(methylidene)boranes MeB=CA₂(A = SiMe₃) and MeB=CAA′ (A′ = SiMe₂Cl) gives the adducts MeB(L)=CA₂ ( 1a , b ; L = trimethylpyridine, PMe₃) and MeB(L)=CAA′ ( 1c , d ; L = di‐ and trimethylpyridine), respectively. Alcohols and amines HX are added to the BC double bond to give boranes MeB(X)—CHA₂ ( 8a — c ; X = OiPr, OtBu, NiPr₂); MeB=CAA′ and HNMe₂ react in the ratio 1:2, yielding MeB(X)—CHA(SiMe₂X) ( 2d ; X = NMe₂). From MeB=CA₂ and BH₃, the five‐membered ring [—CA₂—BH—CA₂—BMe(Hm)₂BMe—] ( 2e ; 2:1) or the six‐membered ring [—CA₂—BH(H_μ)₂BMe—CA₂—BH(H_μ)₂BMe—] ( 2f ; 1:1) are formed, both containing double hydrogen bridges; the product 2f crystallizes in the space group P1¯. The metallocene trihydrides [Cp₂MH₃] add to the BC double bond under formation of a double hydrogen bridge to give [Me(A₂CH)B(H_μ)₂MCp₂] ( 2g , h ; M = Nb, Ta). MeB=CA₂ can be chloroborated, ‐stannated, and ‐phosphated with E—Cl to yield the boryldisilylmethanes MeB(Cl)—CA₂—E ( 2i — l ; E = EtClB, tBuClB, Me₂ClSn, Cl₂P). The alkyloboration and ‐alumination with E—R leads to the boryldisilylmethanes MeBR—SiA₂—E ( 2m — o ; E—R = Me₂B—Me, Et₂B—Et, Cl₂Al—Et) and the bromination to MeB(Br)—CA₂Br. (2+2) Cycloadditions are achieved, when MeB=CA₂ is reacted with unsaturated molecules a=b, yielding four‐membered rings [—BMe—CA₂—b—a—] [ 4a — d ; a=b = fluorenone, bis(methoxycarbonyl)ethyne (reacting at both of the C=O bonds), phenylisocyanate (reacting at the C=O bond), N‐isopropylacetoneimine], or with triple bond systems RC≡Z, yielding four‐membered rings [—BMe—CA₂—Z=CR—] ( 4e — g ; RC≡Z = PhC≡CPh, AC≡CCl, tBuC≡P). With a series of six molecules with an element‐oxygen double bond, a primary (2+2) cycloaddition is followed by a metathetical splitting of the transient four‐membered rings 4h — m . One of the metathesis products is MeB≡O, which is identified as boroxene (MeBO)₃, the other component is an alkene RR′C=CA₂ [starting from MeB=CA₂ and PhCHO, PhC(Me)O] or an alkene RR′C=CAA′ (starting from MeB=CAA′ and PhCHO, tBuCHO) or the methylidene phosphorane Ph₃P=CA₂ (starting from MeB=CA₂ and Ph₃PO) or the dicarbadicobaltatetrahedrane [(CA)₂{Co(CO)₃}₂] {starting from MeB=CA₂ and [Co₂(CO)₈]}. The (2+3) cyclodaddition of MeB=CA₂ to the azide X₂PN₃ (X = NiPr₂) as 1, 3‐dipole gives the five‐membered ring [=BMe—CA₂—N=N—NX=] ( 5a ) and to RN₃ the rings [=BMe—CA=N—NA—NR=] ( 5′b , c ; R = iBu, A; formed from the cycloadducts 5b , c by migration of A); analogously, [=BMe—CA′=N—NA—NA=] ( 5′d ) is formed from MeB=CAA′ and AN₃. Finally, the nitrone O—NMe=CHPh and MeB=CA₂ or MeB=CAA′ give the corresponding (2+3) cycloadducts 5e , f , respectively. All of the products were characterized by their ¹H, ¹¹B, and ¹³C NMR spectra.     

Effects-based chemical category approach for prioritization of low affinity estrogenic chemicals

Regulatory agencies are charged with addressing the endocrine disrupting potential of large numbers of chemicals for which there is often little or no data on which to make decisions. Prioritizing the chemicals of greatest concern for further screening for potential hazard to humans and wildlife is an initial step in the process. This paper presents the collection of in vitro data using assays optimized to detect low affinity estrogen receptor (ER) binding chemicals and the use of that data to build effects-based chemical categories following QSAR approaches and principles pioneered by Gilman Veith and colleagues for application to environmental regulatory challenges. Effects-based chemical categories were built using these QSAR principles focused on the types of chemicals in the specific regulatory domain of concern, i.e. non-steroidal industrial chemicals, and based upon a mechanistic hypothesis of how these non-steroidal chemicals of seemingly dissimilar structure to 17ß-estradiol (E2) could interact with the ER via two distinct binding types. Chemicals were also tested to solubility thereby minimizing false negatives and providing confidence in determination of chemicals as inactive. The high-quality data collected in this manner were used to build an ER expert system for chemical prioritization described in a companion article in this journal.     

Hadronic ϕ production and the lund model for lowp T interactions

Experimental results on inclusive ? production are compared with the Lund model for lowp _T hadronic interactions. The data is based on a sample of 600,000 ? mesons in the kinematic rangep _T <1.0 (GeV/c)² and 0.0<x _F<0.4, produced in π^±,K ^±,p and \(\bar p\) Be interactions at 100 GeV/c and 120 GeV/c incident momentum. The Lund model reproduces the shapes of the longitudinal differential cross sections reasonably well, but the relative cross sections for incident, π,K andp show a discrepancy with the data.