603 research outputs found
How the hydrogen bond in NHF is revealed with Compton scattering
In order to probe electron wave functions involved in the bonding of NHF,
we have performed Compton scattering experiments in an oriented single crystal
and in a powder. Ab initio calculations of the Compton profiles for NHF and
NHCl are used to enlighten the nature of the bonds in the NHF crystal.
As a consequence, we are able to show significant charge transfer in the
ammonium ion which is not observable using other methods. Our study provides a
compelling proof for hydrogen bond formation in NHF.Comment: 4 pages, 5 figures, accepted for publication as a Regular Article in
Physical Review
Hydrogen bonding and coordination in normal and supercritical water from X-ray inelastic scattering
A direct measure of hydrogen bonding in water under conditions ranging from
the normal state to the supercritical regime is derived from the Compton
scattering of inelastically-scattered X-rays. First, we show that a measure of
the number of electrons involved in hydrogen bonding at varying
thermodynamic conditions can be directly obtained from Compton profile
differences. Then, we use first-principles simulations to provide a connection
between and the number of hydrogen bonds . Our study shows that
over the broad range studied the relationship between and is
linear, allowing for a direct experimental measure of bonding and coordination
in water. In particular, the transition to supercritical state is characterized
by a sharp increase in the number of water monomers, but also displays a
significant number of residual dimers and trimers.Comment: 14 pages, 5 figures, 1 tabl
Correlates of Depressive and Anxiety Symptoms in Young Adults with Spina Bifida *
Objective Based on social ecological theory, this study was designed to examine the unique relationships between multi-level ecological factors and psychological symptoms in young adults with spina bifida (SB). Method A sample of 61 individuals with SB, 18–25 years of age, completed standardized self-report measures of attitude toward SB, satisfaction with family functioning, Chronic Care Model (CCM) services, and depressive and anxiety symptoms. A chart review yielded SB clinical data. Results High rates of depressive and anxiety symptoms were found. Hierarchical regression analysis identified the proximal individual (attitude toward SB) and family (satisfaction with family functioning) factors as more strongly related to depressive symptoms than the distal healthcare system factor (CCM services). Self-reported pain was the only ecological factor associated with anxiety symptoms. Conclusions Study findings provide a potential foundation for multi-factor screening of young adults with SB at risk for psychological symptoms
Oxygen disorder in ice probed by X-ray Compton scattering
We use electron momentum density in ice as a tool to quantify order-disorder
transitions by comparing Compton profiles differences of ice VI, VII, VIII and
XII with respect to ice Ih. Quantitative agreement is found between theory and
experiment for ice VIII, which is the most ordered phase. Robust signatures of
the oxygen disorder are identified in the momentum density for the VIII-VII ice
phase transition. The unique aspect of this work is the determination of the
fraction n_e of electron directly involved in phase transitions as well as the
use of position space signatures for quantifying oxygen site disorder.Comment: 3 figures, 2 tables. Accepted for publication in Phys. Rev.
Untyping Typed Algebras and Colouring Cyclic Linear Logic
We prove "untyping" theorems: in some typed theories (semirings, Kleene
algebras, residuated lattices, involutive residuated lattices), typed equations
can be derived from the underlying untyped equations. As a consequence, the
corresponding untyped decision procedures can be extended for free to the typed
settings. Some of these theorems are obtained via a detour through fragments of
cyclic linear logic, and give rise to a substantial optimisation of standard
proof search algorithms.Comment: 21
Observed communication semantics for classical processes
Classical Linear Logic (CLL) has long inspired readings of its proofs as communicating processes. Wadler's CP calculus is one of these readings. Wadler gave CP an operational semantics by selecting a subset of the cut-elimination rules of CLL to use as reduction rules. This semantics has an appealing close connection to the logic, but does not resolve the status of the other cut-elimination rules, and does not admit an obvious notion of observational equivalence. We propose a new operational semantics for CP based on the idea of observing communication, and use this semantics to define an intuitively reasonable notion of observational equivalence. To reason about observational equivalence, we use the standard relational denotational semantics of CLL. We show that this denotational semantics is adequate for our operational semantics. This allows us to deduce that, for instance, all the cut-elimination rules of CLL are observational equivalences
Sessions as Propositions
Recently, Wadler presented a continuation-passing translation from a
session-typed functional language, GV, to a process calculus based on classical
linear logic, CP. However, this translation is one-way: CP is more expressive
than GV. We propose an extension of GV, called HGV, and give translations
showing that it is as expressive as CP. The new translations shed light both on
the original translation from GV to CP, and on the limitations in
expressiveness of GV.Comment: In Proceedings PLACES 2014, arXiv:1406.331
Type 3c (pancreatogenic) diabetes mellitus secondary to chronic pancreatitis and pancreatic cancer
Diabetes mellitus is a group of diseases defined by persistent hyperglycaemia. Type 2 diabetes, the most prevalent form, is characterised initially by impaired insulin sensitivity and subsequently by an inadequate compensatory insulin response. Diabetes can also develop as a direct consequence of other diseases, including diseases of the exocrine pancreas. Historically, diabetes due to diseases of the exocrine pancreas was described as pancreatogenic or pancreatogenous diabetes mellitus, but recent literature refers to it as type 3c diabetes. It is important to note that type 3c diabetes is not a single entity; it occurs because of a variety of exocrine pancreatic diseases with varying mechanisms of hyperglycaemia. The most commonly identified causes of type 3c diabetes are chronic pancreatitis, pancreatic ductal adenocarcinoma, haemochromatosis, cystic fibrosis, and previous pancreatic surgery. In this Review, we discuss the epidemiology, pathogenesis, and clinical relevance of type 3c diabetes secondary to chronic pancreatitis and pancreatic ductal adenocarcinoma, and highlight several important knowledge gaps
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