cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.5517/ccp1ghn
title: CCDC 627021: Experimental Crystal Structure Determination

description: Related Article: Shengchun Chen, Mingyang He, Kang Yan, Qun Chen, Yi Guo, Yifeng Zhang|2007|Inorg.Chem.Commun.|10|451|doi:10.1016/j.inoche.2006.12.020
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.13140/rg.2.2.26342.52804
title: Can ginger treat diabetics 2
DOI: 10.3535/1bz-an7-b8j
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/cc9mf1c
title: CCDC 286782: Experimental Crystal Structure Determination

description: Related Article: D.Shingnapurkar, R.Butcher, Z.Afrasiabi, E.Sinn, F.Ahmed, F.Sarkar, S.Padhye|2007|Inorg.Chem.Commun.|10|459|doi:10.1016/j.inoche.2006.12.016
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/13l-4ha-ecn
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccp41ys
title: CCDC 629515: Experimental Crystal Structure Determination

description: Related Article: D.Shingnapurkar, R.Butcher, Z.Afrasiabi, E.Sinn, F.Ahmed, F.Sarkar, S.Padhye|2007|Inorg.Chem.Commun.|10|459|doi:10.1016/j.inoche.2006.12.016
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/0sv-5rt-31y
title: Dianthus subacaulis Vill.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccp5gx6
title: CCDC 630878: Experimental Crystal Structure Determination

description: Related Article: D.Shingnapurkar, R.Butcher, Z.Afrasiabi, E.Sinn, F.Ahmed, F.Sarkar, S.Padhye|2007|Inorg.Chem.Commun.|10|459|doi:10.1016/j.inoche.2006.12.016
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/kg6-cd1-8dv
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/ab4-805-em5
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/jbl-zj6-5g1
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.13140/rg.2.2.32778.16327
title: Current Situation: Villager's PV Module at Village Nat Kan Lel
DOI: 10.15468/dl.5eegcw
title: Occurrence Download

description: A dataset containing 8230 species occurrences available in GBIF matching the query:
{
 "and" : [
 "BasisOfRecord is one of (Observation, Human Observation)",
 "Geometry POLYGON((-100.07892 18.2153,-97.81736 18.2153,-97.81736 20.27292,-100.07892 20.27292,-100.07892 18.2153))",
 "HasGeospatialIssue is false",
 "OccurrenceStatus is Present",
 "TaxonKey is Spatula discors",
 "Year 1960-2025"
 ]
}

 The dataset includes 8230 records from 4 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0029137-251009101135966/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.3535/1kp-rse-2yx
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.6084/m9.figshare.30379507.v1
title: Datos metodológicos de los estudios seleccionados

description: Información metodológica: Incluye la identificación y análisis de las estrategias de aprendizaje, constructo teórico, instrumentos de recolección y herramientas tecnológicas digitales que se referencian en los estudios seleccionados para apoyar la autorregulación del aprendizaje en Colombia.
DOI: 10.3535/y12-ehb-cw4
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/ktz-cjn-24x
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/xdn-7vh-9t9
title: Dianthus superbus subsp. alpestris Kablík. & Čelak.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.6084/m9.figshare.30379477.v2
title: Datos generales

description: Contiene los datos generales del estudio: Identificador único del estudio (ID), consecutivo, título, alcance, año de publicación, autor(es), universidad de origen del autor(es), origen del autor, ubicación geográfica, área de conocimiento, nivel de educación, modalidad educativa, tipo de estudio y muestra poblacional.
DOI: 10.3535/yaa-1gv-50y
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.6084/m9.figshare.30379477.v1
title: Datos generales Estudios seleccionados

description: Contiene los datos generales del estudio: Identificador único del estudio (ID), consecutivo, título, alcance, año de publicación, autor(es), universidad de origen del autor(es), origen del autor, ubicación geográfica, área de conocimiento, nivel de educación, modalidad educativa, tipo de estudio y muestra poblacional.
DOI: 10.3535/61g-ywv-qbd
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/sh0-t9v-hpk
title: Dianthus strictus Banks & Sol.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.15468/dl.xgnskj
title: Occurrence Download

description: A dataset containing 2223 species occurrences available in GBIF matching the query:
{
 "and" : [
 "Country is Colombia",
 "OccurrenceStatus is Present",
 "TaxonKey is Myliobatiformes"
 ]
}

 The dataset includes 2223 records from 125 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0029138-251009101135966/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.3535/j6s-lrf-6hl
title: Dianthus subacaulis subsp. brachyanthus (Boiss.) P. Fourn.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.6084/m9.figshare.30379507
title: Datos metodológicos

description: Información metodológica: Incluye la identificación y análisis de las estrategias de aprendizaje, constructo teórico, instrumentos de recolección y herramientas tecnológicas digitales que se referencian en los estudios seleccionados para apoyar la autorregulación del aprendizaje en Colombia.
DOI: 10.13140/rg.2.2.23288.55049
title: [SNB] Solo Negocios Bulletin 4/13/18
DOI: 10.3535/cgv-rtp-gp5
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.13140/rg.2.2.30733.44002
title: GenBank MF540536 1
DOI: 10.3535/5mr-dt5-xqq
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.13140/rg.2.2.32411.16161
title: Weissella sp. strain confusa 16S ribosomal RNA gene, partial sequence GenBank: MF480335.1
DOI: 10.3535/n27-jg6-mfa
title: Lantana trifolia L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.6084/m9.figshare.30379267
title: <b>Supplementary Material – Thiophene-triazole hybrids inhibit the major toxic activities </b><b>of </b><b><i>Bothrops jararacussu</i></b><b> venom</b>

description: <b>Table S1 – </b><b>Values of the plasma coagulant activity of </b><b><i>Bothrops jararacussu</i></b><b> venom.</b><b>Table S2 – </b><b>Values of the proteolytic activity of </b><b><i>Bothrops jararacussu</i></b><b> venom.</b><b>Table S3 – </b><b>Values of the PLA2 activity of </b><b><i>Bothrops jararacussu</i></b><b> v</b><b>enom.</b><br>
DOI: 10.6084/m9.figshare.30376381
title: <b>BOS as a Novel Strategy for Bone Regeneration</b>

description: Background: Bone regeneration after critical-size defects remains a major clinical challenge, and current grafting approaches are limited by their morbidity, immunogenicity, and availability. Pharmacological strategies that harness the potential of endogenous stem cells offer a promising alternative. Endothelin-1 (ET-1), a potent vasoactive peptide, exerts context-dependent effects on bone remodeling through ETA and ETB receptors. Excessive ET-1 signaling is associated with osteoclast activation, inflammation, and bone loss, suggesting that endothelin receptor antagonists like Bosentan (BOS) may provide skeletal benefits. Objective: To investigate whether BOS, a clinically approved dual ETA/ETB antagonist currently used for pulmonary arterial hypertension, can be repositioned to promote osteogenesis in human periodontal ligament stem cells (hPDLSCs). Methods: hPDLSCs were isolated and characterized according to mesenchymal stem cell criteria. Cells were treated with increasing concentrations of BOS (10–40 µM), and assays were performed to evaluate cytotoxicity (MTT), migration (scratch assay), mineralization (Alizarin Red S staining), alkaline phosphatase (ALP) activity, and gene expression of osteogenic (RUNX2, OPG, CTNNB1) and inflammatory (TNF-α) markers. Results: BOS was non-cytotoxic at all tested concentrations. At 30–40 µM, BOS significantly enhanced cell migration, mineralized nodule formation, and ALP activity compared to osteogenic controls (p &lt; 0.05). Gene expression analyses revealed marked upregulation of RUNX2, OPG, and CTNNB1, alongside suppression of TNF-α, indicating simultaneous stimulation of osteogenesis and attenuation of proinflammatory signaling. Conclusion: BOS augments hPDLSC-mediated osteogenesis by activating osteoblastogenic pathways, enhancing mineralization, and reducing inflammatory cytokine expression. These findings suggest that BOS is a promising candidate for drug repurposing in bone regeneration.
DOI: 10.3535/m5v-r3g-rta
title: Dianthus strictus Banks & Sol.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.13140/rg.2.2.33459.73769
title: A Formula Connecting Fourier Series and Fourier Transform
DOI: 10.13140/rg.2.2.29676.67201
title: Rectangular Zernikes
DOI: 10.5517/ccnl48m
title: CCDC 613250: Experimental Crystal Structure Determination

description: Related Article: Y.Sevryugina, M.A.Petrukhina|2007|Z.Krist.Cryst.Mater.|222|34|doi:10.1524/zkri.2007.222.1.34
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/heq-ws2-yge
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/s85-rhs-ezy
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccn6bx2
title: CCDC 601924: Experimental Crystal Structure Determination

description: Related Article: M.U.Schmidt, C.Buchsbaum, J.M.Schnorr, D.W.M.Hofmann, M.Ermrich|2007|Z.Krist.Cryst.Mater.|222|30|doi:10.1524/zkri.2007.222.1.30
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.5517/ccn9wwp
title: CCDC 605333: Experimental Crystal Structure Determination

description: Related Article: A.Karadag|2007|Z.Krist.Cryst.Mater.|222|39|doi:10.1524/zkri.2007.222.1.39
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.5281/zenodo.17372410
title: Research data for the paper "Constrained Multi-Robot Task Allocation for Mobile Robots: Handling Heterogeneity, Time Windows, Precedence, and Batches"

description: This dataset contains the results of our conducted experiments and descriptions for our used task and robot models.
DOI: 10.3535/erk-rnh-r5x
title: Lantana mista L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5281/zenodo.17372409
title: Research data for the paper "Constrained Multi-Robot Task Allocation for Mobile Robots: Handling Heterogeneity, Time Windows, Precedence, and Batches"

description: This dataset contains the results of our conducted experiments and descriptions for our used task and robot models.
DOI: 10.5517/ccnym28
title: CCDC 624280: Experimental Crystal Structure Determination

description: Related Article: R.Kutsumizu, H.Shinmori, T.Takeuchi|2007|Tetrahedron Lett.|48|3225|doi:10.1016/j.tetlet.2007.03.028
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/7jr-xsx-lhh
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/ath-06y-bkj
title: Dianthus strictus var. axilliflorus (Fenzl) Reeve

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppwjr
title: CCDC 646645: Experimental Crystal Structure Determination

description: Related Article: Ming-Lin Guo, Chen-Hu Guo, Hui-Zhen Li, Hong Chang|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1456|doi:10.1107/S1600536807018351
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/5vk-dnb-5ym
title: Dianthus strictus var. gracilior (Boiss.) Reeve

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppwks
title: CCDC 646646: Experimental Crystal Structure Determination

description: Related Article: Xin-Qiang Wang, Jian-Dong Fan, Wen-Tao Yu, Dong Xu, Wei-Liang Liu|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1461|doi:10.1107/S1600536807016984
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/acv-q70-5xd
title: Dianthus strictus Banks & Sol.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/2h6-mlf-v2h
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/kfp-y3y-pal
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppwmv
title: CCDC 646648: Experimental Crystal Structure Determination

description: Related Article: Ming-Lin Guo, Chen-Hu Guo, Hui-Zhen Li, Hong Chang|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1471|doi:10.1107/S1600536807019423
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/nph-mgw-b8k
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppwnw
title: CCDC 646649: Experimental Crystal Structure Determination

description: Related Article: Huan-Xin Liu, Xiao Jiang, Yun-xiao Liang|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1472|doi:10.1107/S1600536807019332
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/lnw-313-1y2
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/7cf-87z-mhy
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/b27-yfq-f1a
title: Lantana lilacina Desf.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppws0
title: CCDC 646653: Experimental Crystal Structure Determination

description: Related Article: Su-Ni Qin, Fu-Pei Liang, Zi-Lu Chen, Wei-Hong Yan|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1492|doi:10.1107/S1600536807018417
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/4zv-0ve-89t
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppwt1
title: CCDC 646654: Experimental Crystal Structure Determination

description: Related Article: Minna Cao, Shao-Min Shi, Fei-Hua Luo, Cui-Xia Cheng, Zong-Qiu Hu|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1494|doi:10.1107/S1600536807019514
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/zjj-dl4-ztn
title: Dianthus strictus var. strictus Banks & Sol.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.3535/q32-q9k-v1h
title: Dianthus superbus L.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppww3
title: CCDC 646656: Experimental Crystal Structure Determination

description: Related Article: Yan-Jun Hou, Zhi-Zhong Sun, Ying-Hui Yu, Bai-Yan Li, Guang-Feng Hou|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1506|doi:10.1107/S1600536807019472
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/qnm-flb-dym
title: Lantana lilacina Desf.

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.34740/kaggle/dsv/13408217
title: Peer-to-Peer Boliviano (BOB) Exchange Data
DOI: 10.5517/ccppwx4
title: CCDC 646657: Experimental Crystal Structure Determination

description: Related Article: Ya-Min Li, Jing-Lai Zhang, Xiao-Wei Zhao|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1510|doi:10.1107/S1600536807019599
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.5517/ccppwy5
title: CCDC 646658: Experimental Crystal Structure Determination

description: Related Article: Zhu-Yan Zhang, Shan Gao, Li-Hua Huo, Jing-Gui Zhao|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1514|doi:10.1107/S1600536807020533
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.3535/z4w-bz5-js2
title: Dianthus strictus var. gracilior (Boiss.) Reeve

description: Digital Specimen for the physical specimen hosted at Natural History Museum Vienna.
DOI: 10.5517/ccppwz6
title: CCDC 646659: Experimental Crystal Structure Determination

description: Related Article: Yan-Jun Hou, Zhi-Zhong Sun, Ying-Hui Yu, Bai-Yan Li, Guang-Feng Hou|2007|Acta Crystallogr.,Sect.E:Struct.Rep.Online|63|m1519|doi:10.1107/S1600536807020041
description: An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
DOI: 10.6084/m9.figshare.30109465
title: ExtendedData1_EGG USA FINALExtendedData2_EGG_MONG_FINALExtendedData3_DeepEddie_LAIPMS_GEOCHRON_2020CExtendedData4_Mussentuchit_CA-TIMS U-Pb data table_Mar2023

description: Supplementary Files for: <b>U-Pb calcite age dating of fossil eggshell as an accurate deep time geochronometer</b>