When a heavy atomic nucleus splits (fission), the resulting fragments are observed to emerge spinning
; this phenomenon has been a mystery in nuclear physics for over 40 years
. The internal ...generation of typically six or seven units of angular momentum in each fragment is particularly puzzling for systems that start with zero, or almost zero, spin. There are currently no experimental observations that enable decisive discrimination between the many competing theories for the mechanism that generates the angular momentum
. Nevertheless, the consensus is that excitation of collective vibrational modes generates the intrinsic spin before the nucleus splits (pre-scission). Here we show that there is no significant correlation between the spins of the fragment partners, which leads us to conclude that angular momentum in fission is actually generated after the nucleus splits (post-scission). We present comprehensive data showing that the average spin is strongly mass-dependent, varying in saw-tooth distributions. We observe no notable dependence of fragment spin on the mass or charge of the partner nucleus, confirming the uncorrelated post-scission nature of the spin mechanism. To explain these observations, we propose that the collective motion of nucleons in the ruptured neck of the fissioning system generates two independent torques, analogous to the snapping of an elastic band. A parameterization based on occupation of angular momentum states according to statistical theory describes the full range of experimental data well. This insight into the role of spin in nuclear fission is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the γ-ray heating problem in nuclear reactors
, for the study of the structure of neutron-rich isotopes
, and for the synthesis and stability of super-heavy elements
.
Despite the existence of an established convention for abbreviating rock-forming minerals (Kretz, 1983), there is still a wide range of symbols used in the clay minerals community that often follow ...no common set of rules. Following a check of 166 post-millennium research articles (not journal-specific) in the author's literature collection, which were compiled using the Internet search words ‘clay minerals’ and ‘quantification’, a total of 472 mineral abbreviations common to clay materials and clay-sized (<2 μm) fractions were examined. The compilation of abbreviations is also largely compatible with The Canadian Mineralogist symbol list of rock- and ore-forming minerals (https://www.mineralogicalassociation.ca/wordpress/wp-content/uploads/2020/01/symbols.pdf). Mineral name Symbol Status Mineral name Symbol Status Aliettite Ali Rd Laumontite (a, b, c, d) Lmt A Allophane Alp G Lennilenapeite Lnl A Aluminoceladonite Acel A Lepidocrocite (d) Lpc A Amesite (c) Ame G Lepidolite (a, b, c, d) Lpd GROUP Anandite Ana A Lithiophorite Lpr G Annite (a, b, c, d) Ann A Lizardite (a, b, c, d) Lz G Antigorite (a, b, c, d) Atg Rd Lobanovite Lbv A Armbrusterite Abr A Loughlinite (d) Lou A Aspidolite (d) Asp Rd Magadiite Mgd A Astrophyllite (d) Ast G Manandonite Mnd G Baileychlore Blc A Manganarsite Mna A Balestraite Bls A Manganite Mnn G Bannisterite Ban A Manganosite (c) Mng G Bayerite Byr G Manjiroite Mji A Beidellite (c) Bei G Margarite (a, b, c) Mrg A Bementite Bem Rd Masutomilite Msu A Berthierine (d) Brh G Mcgillite Mcg A Biotite (a, b, c, d) Bt GROUP Meixnerite Mxn A Birnessite Bir G Mica (b) Mca GROUP Bityite Bty A Minehillite Mhl A Bixbyite (c) Bxb G Minnesotaite (b, c) Mns G Böhmite (a, b, c, d) Bhm G Mogánite (c) Mog Rn Borocookeite Bckt A Montdorite Mdr Rd Boromuscovite Bms A Montmorillonite (a, b, c, d) Mnt G Brammalite Bml GROUP Mordenite (c, d) Mor A Brindleyite Bly A Motukoreaite Mtu Q Brinrobertsite Brb A (ML) Mountkeithite Mke A Brucite (a, b, c, d) Brc G Muscovite (a, b, c, d) Ms A Bulgakite Bgk A Nacrite Ncr G Buserite Bsr A Nafertisite Naf A Cairncrossite Ccs A Nalivkinite Nlv A Carlosturanite Csr A Nanpingite Npg A Carrboydite Cby Q Nelenite Nln A Caryopilite (d) Cpl A Népouite Npo G Celadonite (b, c, d) Cel A Nimite Nim A Chalcophanite Cph G Niobokupletskite Nbk A Chamosite (b, c, d) Chm G Niobophyllite Nbp A Chernykhite Cyk A Nontronite Non A Chlormagaluminite Cma A Nordstrandite Nsd A Chlorite (a, b, c, d) Chl GROUP Norrishite Nrr A Chlorite-serpentine Chl-Srp ML Nsutite Nsu A Chlorite-smectite Chl-Sme ML Odinite Odn A Chromphyllite Crp A Opal (c) Opl G Chrysotile (a, b, c, d) Ctl Rd Orlymanite Orl A Clinochlore (b, c) Clc G Oxykinoshitalite Okns A Clinoptilolite (c, d) Cpt A Palygorskite (c) Plg G Clinotobermorite Ctbm Rd Paragonite (a, b, c, d) Pg A Clintonite Cln A Parsettensite Psn G Coalingite Clg A Pecoraite Pco A Cookeite (d) Ckt Rd Pennantite Pnn G Coombsite Cmb A Perraultite Prt Rd Coronadite Cor G Phillipsite (c) Php A Corrensite (c, d) Crr G (ML) Phlogopite (a, b, c, d) Phl G Cristobalite (a, b, c, d) Crs A Plombièrite Plm Rd Cronstedtite Cro G Polylithionite (d) Pln A Cryptomelane Cml A Preiswerkite Pwk A Desautelsite Des A Priderite Pdr G Devitoite Dvt A Pyroaurite (d) Pya Rd Diaspore (a, b, c, d) Dsp G Pyrochroite (d) Pyc G Dickite (c, d) Dck G Pyrolusite (d) Pyl A Donbassite Dbs G Pyrophyllite (a, b, c, d) Prl G Dozyite Doz G Pyrosmalite Pys Rd Eastonite (c, d) Eas Rd Quartz (c) Qz A Eggletonite Egg A Raite Rai A Ephesite Eph A Roscoelite (d) Rcl A Erionite (c) Eri A Saliotite (d) Sal A Falcondoite Fcd A Saponite (c, d) Sap G Fedorite Fdr A Sauconite Sau G Feitknechtite Fkn A Schallerite Slr G Ferrihollandite Fhol A Seidozerite Sdz Rd Ferrihydrite Fhy A Sepiolite (b, c, d) Sep G Ferripyrophyllite Fprl A Serpentine (a, b, c, d) Srp GROUP Ferrisepiolite Fsep A Shafranovskite Sfn A Ferroaluminoceladonite Facel Rn Shirokshinite (d) Shk A Ferroceladonite (c) Fcel A Siderophyllite (d) Sid A Ferrokinoshitalite Fkns A Smectite (b, c) Sme GROUP Ferrosaponite Fsap A Smectite-talc Sme-Tlc ML Foshagite (c, d) Fos G Stevensite (c) Stv Q Fraipontite Fpt G Stichtite Stt Rd Franklinfurnaceite Fkf A Stilbite (a, b, c, d) Stb A Franklinphilite Fkp A Stilpnomelane (a, b, c, d) Stp A Friedelite Fdl G Strontiomelane Sml A Ganophyllite Gnp G Sudoite (c) Sud Rd Ganterite Gtr A Suhailite Suh A Gibbsite (a, b, c, d) Gbs A Svanbergite Svb A Glagolevite Ggl A Swinefordite Sfd A Glauconite (a, b, c, d) Glt GROUP Tainiolite (d) Tai G Glauconite-smectite Glt-Sme ML Takanelite Tkn A Goethite (c) Gth A Takovite Tkv A Gonyerite Gye G Talc (a, b, c, d) Tlc G Greenalite (b, c, d) Gre G Tarbagataite Tbg A Groutite Gro G Tetraferriannite Tfann Rn Guidottiite Gdt A Tetraferriphlogopite Tfphl Rn Gyrolite Gyr G Tobelite Tbl A Halloysite Hly G Tobermorite Tbm Rd Hausmannite (d) Hsm G Todorokite Tdr A Hectorite Htr Q Tosudite Tos G (ML) Hendricksite Hds A Tridymite (a, b, c, d) Trd G Henrymeyerite (d) Hmy A Trilithionite (d) Tln Rd Heulandite (a, b, c, d) Hul A Truscottite Tst G Hisingerite Hsg G Tuperssuatsiaite Tup A Hollandite (d) Hol Rd Varennesite Vrn A Honessite Hon A Vermiculite (a, b, c, d) Vrm G Hydrobiotite Hbt Rd (ML) Vernadite Vnd Q Hydrohonessite Hhon A Volkonskoite Vkn Rd Hydrotalcite (d) Htc GROUP Wairakite (b, c, d) Wrk A Hydroxide-interlayered smectite HIS ML Wermlandite Wld A Hydroxide-interlayered vermiculite HIV ML Willemseite Wls A Illite (c) Ilt GROUP Windhoekite
There is strong circumstantial evidence that certain heavy, unstable atomic nuclei are 'octupole deformed', that is, distorted into a pear shape. This contrasts with the more prevalent rugby-ball ...shape of nuclei with reflection-symmetric, quadrupole deformations. The elusive octupole deformed nuclei are of importance for nuclear structure theory, and also in searches for physics beyond the standard model; any measurable electric-dipole moment (a signature of the latter) is expected to be amplified in such nuclei. Here we determine electric octupole transition strengths (a direct measure of octupole correlations) for short-lived isotopes of radon and radium. Coulomb excitation experiments were performed using accelerated beams of heavy, radioactive ions. Our data on (220)Rn and (224)Ra show clear evidence for stronger octupole deformation in the latter. The results enable discrimination between differing theoretical approaches to octupole correlations, and help to constrain suitable candidates for experimental studies of atomic electric-dipole moments that might reveal extensions to the standard model.
A hydroxy-sodalite/cancrinite zeolite composite was synthesized from low-grade calcite-bearing kaolin by hydrothermal alkali-activation method at 160 °C for 6 h. The effect of calcite addition on the ...formation of the hydroxy-sodalite/cancrinite composite was investigated using artificial mixtures. The chemical composition and crystal morphology of the synthesized zeolite composite were characterized by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption analyses. The average specific surface area is around 17–20 m2·g−1, whereas the average pore size lies in the mesoporous range (19–21 nm). The synthesized zeolite composite was used as an adsorbent for the removal of heavy metals in aqueous solutions. Batch experiments were employed to study the influence of adsorbent dosage on heavy metal removal efficiency. Results demonstrate the effective removal of significant quantities of Cu, Pb, Ni, and Zn from aqueous media. A comparative study of synthesized hydroxy-sodalite and hydroxy-sodalite/cancrinite composites revealed the latter was 16–24% more efficient at removing heavy metals from water. The order of metal uptake efficiency for these zeolites was determined to be Pb > Cu > Zn > Ni. These results indicate that zeolite composites synthesized from natural calcite-bearing kaolin materials could represent effective and low-cost adsorbents for heavy metal removal using water treatment devices in regions of water shortage.
Computer X-ray microtomography (µXCT) represents a powerful tool for
investigating the physical properties of porous rocks. While calculated
porosities determined by this method typically match ...experimental
measurements, computed permeabilities are often overestimated by more than
1 order of magnitude. This effect increases towards smaller pore sizes, as
shown in this study, in which nanostructural features related to clay
minerals reduce the permeability of tight reservoir sandstone samples.
Focussed ion beam scanning
electron microscopy (FIB-SEM) tomography was applied to determine the permeability effects of
illites at the nanometre scale, and Navier–Stokes equations were applied to
calculate the permeability of these domains. With these data, microporous
domains (porous voxels) were defined using microtomography images of a tight
reservoir sample. The distribution of these domains could be extrapolated by
calibration against size distributions measured in FIB-SEM images. For this,
we assumed a mean permeability for the dominant clay mineral (illite) in the
rock and assigned it to the microporous domains within the structure. The
results prove the applicability of our novel approach by combining FIB-SEM
with X-ray tomographic rock core scans to achieve a good correspondence
between measured and simulated permeabilities. This methodology results in a
more accurate representation of reservoir rock permeability in comparison to
that estimated purely based on µXCT images.
Pilot sites are currently used to test the performance of bentonite barriers for sealing high-level radioactive waste repositories, but the degree of mineral stability under enhanced thermal ...conditions remains a topic of debate. This study focuses on the SKB ABM5 experiment, which ran for 5 years (2012 to 2017) and locally reached a maximum temperature of 250 °C. Five bentonites were investigated using XRD with Rietveld refinement, SEM-EDX and by measuring pH, CEC and EC. Samples extracted from bentonite blocks at 0.1, 1, 4 and 7 cm away from the heating pipe showed various stages of alteration related to the horizontal thermal gradient. Bentonites close to the contact with lower CEC values showed smectite alterations in the form of tetrahedral substitution of Si4+ by Al3+ and some octahedral metal substitutions, probably related to ferric/ferrous iron derived from corrosion of the heater during oxidative boiling, with pyrite dissolution and acidity occurring in some bentonite layers. This alteration was furthermore associated with higher amounts of hematite and minor calcite dissolution. However, as none of the bentonites showed any smectite loss and only displayed stronger alterations at the heater–bentonite contact, the sealants are considered to have remained largely intact.
There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, ...which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we observed the low-lying quantum states in
Rn and
Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.
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