Advancements in internationally accepted standards for radiation processing

Three subcommittees of the American Society for Testing and Materials (ASTM) are developing standards on various aspects of radiation processing. Subcommittee E10.01 “Dosimetry for Radiation Processing” has published 9 standards on how to select and calibrate dosimeters, where to put them, how many to use, and how to use individual types of dosimeter systems. The group is also developing standards on how to use gamma, electron beam, and x-ray facilities for radiation processing, and a standard on how to treat dose uncertainties. Efforts are underway to promote inclusion of these standards into procedures now being developed by government agencies and by international groups such as the United Nations' International Consultative Group on Food Irradiation (ICGFI) in order to harmonize regulations and help avoid trade barriers.

Subcommittee F10.10 “Food Processing and Packaging” has completed standards on good irradiation practices for meat and poultry and for fresh fruits, and is developing similar standards for the irradiation of seafood and spices. These food-related standards are based on practices previously published by ICGFI.

Subcommittee E10.07 on “Radiation Dosimetry for Radiation Effects on Materials and Devices” principally develops standards for determining doses for radiation hardness testing of electronics. Some, including their standards on the Fricke and TLD dosimetry systems are equally useful in other radiation processing applications.     

Molecular Modeling of the 1,1-Cyclopropane- and 1,1-Cyclobutanedicarboxamide Systems. Insights into the Self-Assembly of Diamide Diacids in Water

Modeling of the following compounds bis-(N--amido-L-phenylalaninyl)-1,1-cyclopropane dicarboxylate, 3, and bis-(N--amido-L-phenylalaninyl)-1,1-cyclobutane dicarboxylate, 4, were undertaken. The study involved construction and optimization of the precursory 1,1-dicarboxaldehydes and continued stepwise via the 1,1-dicarboxamides, the bis-N-(methyl)dicarboxamides, the bis(N--amidoglycinyl) dicarboxylates, the bis(N--amido-L-alaninyl) dicarboxylates and onto the targeted bis(N--amido-L-phenylalaninyl) dicarboxylates. Using the X-ray crystal structure of 4 (i.e., 4X) as a guide, we found that our approach was not able to reproduce the packable conformer of 4, via the computational methods employed. Nevertheless, an enhanced understanding of the intramolecular hydrogen bonding patterns available to these systems was obtained from IR and VT-NMR studies. In summary, the conformational preferences found in the 1,1-disubstituted cycloalkanes (3 and 4) direct their respective self-assembly processes by controlling the orientation of their amide NH populations.     

Synthesis and characterization of N(1)-(4-toluenesulfonyl)-N(1)- (9-anthracenemethyl)triamines

A modular synthetic approach was developed to access triamines with varying tether lengths from commercially available aminoalkanols. Initial N-alkylation via reductive amination with anthracene-9-carbaldehyde provided the secondary amines in good yield. Subsequent ditosylation with excess TsCl yielded the respective bis-N,O-tosylates. The tosylates were reacted with excess putrescine to give the final triamines. X-ray crystallography revealed that the polyamine tail is preferentially oriented over the shielding cone of the anthracene ring.     

DISTINGUISHED PRE-NICHOLS ALGEBRAS

We formally define and study the distinguished pre-Nichols algebra \( \tilde{B} \)(V) of a braided vector space of diagonal type V with finite-dimensional Nichols algebra B(V). The algebra \( \tilde{B} \)(V) is presented by fewer relations than B(V), so it is intermediate between the tensor algebra T(V) and B(V). Prominent examples of distinguished pre-Nichols algebras are the positive parts of quantized enveloping (super)algebras and their multiparametric versions. We prove that these algebras give rise to new examples of Noetherian pointed Hopf algebras of finite Gelfand-Kirillov dimension. We investigate the kernel (in the sense of Hopf algebras) of the projection from \( \tilde{B} \)(V) to B(V), generalizing results of De Concini and Procesi on quantum groups at roots of unity.     

Shadows Of Mapping Class Groups: Capturing Convex Cocompactness

We strengthen the analogy between convex cocompact Kleinian groups and convex cocompact subgroups of the mapping class group of a surface in the sense of B. Farb and L. Mosher. Received: August 2006, Accepted: January 2007, Revision: February 2007     

THF-FER沸石的系列研究IV.固体酸性及C5烯烃骨架异构化催化性能

在四氢呋喃(THF)-Na2O-SiO2-Al2O3-H2O体系中水热合成的THF-FER沸石,经酸交换／焙烧或焙烧／酸交换处理可制得H-FER-1和H-FER-2两种H型沸石．红外光谱及NH3-TPD等实验结果表明,两者的强酸位主要是对烯烃骨架异构化反应有贡献的Bronsted酸位．1073K／10h的高温水蒸汽处理会导致沸石骨架脱铝,但并未产生过多的末端硅羟基．两者比较,H-FER-1沸石的结构缺陷较少,Bronsted酸位较多,骨架更完美．由THF-FER沸石制备的H-FER催化剂,对C5正构烯烃骨架异构化反应显示了优良的催化活性、选择性及稳定性．     

Absorption of dilaton partial waves by D3-branes

We calculate the leading term in the low-energy absorption cross section for an arbitrary partial wave of the dilaton field by a stack of many coincident D3-branes. We find that it precisely reproduces the semiclassical absorption cross section of a 3-brane geometry, including all numerical factors. The crucial ingredient in making the correspondence is the identification of the precise operators on the D3-brane world-volume which couple to the dilaton field and all its derivatives. The needed operators are related through T-duality and the IIA/M-theory correspondence to the recently determined M(atrix) theory expressions for multiple moments of the 11D supercurrent. These operators have a characteristic symmetrized trace structure which plays a key combinatorial role in the analysis for the higher partial waves. The results presented here give new evidence for an infinite family of non-renormalization theorems which are believed to exist for two-point functions in N=4 gauge theory in four dimensions.     

Reversible Switching between Highly Porous and Nonporous Phases of an Interpenetrated Diamondoid Coordination Network That Exhibits Gate‐Opening at Methane Storage Pressures

Herein, we report that a new flexible coordination network, NiL₂ (L=4‐(4‐pyridyl)‐biphenyl‐4‐carboxylic acid), with diamondoid topology switches between non‐porous (closed) and several porous (open) phases at specific CO₂ and CH₄ pressures. These phases are manifested by multi‐step low‐pressure isotherms for CO₂ or a single‐step high‐pressure isotherm for CH₄. The potential methane working capacity of NiL₂ approaches that of compressed natural gas but at much lower pressures. The guest‐induced phase transitions of NiL₂ were studied by single‐crystal XRD, in situ variable pressure powder XRD, synchrotron powder XRD, pressure‐gradient differential scanning calorimetry (P‐DSC), and molecular modeling. The detailed structural information provides insight into the extreme flexibility of NiL₂ . Specifically, the extended linker ligand, L , undergoes ligand contortion and interactions between interpenetrated networks or sorbate–sorbent interactions enable the observed switching.     

Adaptive Chemical Networks under Non‐Equilibrium Conditions: The Evaporating Droplet

Non‐volatile solutes in an evaporating drop experience an out‐of‐equilibrium state due to non‐linear concentration effects and complex flow patterns. Here, we demonstrate a small molecule chemical reaction network that undergoes a rapid adaptation response to the out‐of‐equilibrium conditions inside the droplet leading to control over the molecular constitution and spatial arrangement of the deposition pattern. Adaptation results in a pronounced coffee stain effect and coupling to chemical concentration gradients within the drop is demonstrated. Amplification and suppression of network species are readily identifiable with confocal fluorescence microscopy. We anticipate that these observations will contribute to the design and exploration of out‐of‐equilibrium chemical systems, as well as be useful towards the development of point‐of‐care medical diagnostics and controlled deposition of small molecules through inkjet printing.