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Principles Of Fluorescence Spectroscopy

Catalysis with chiral secondary amines (asymmetric aminocatalysis) has become a well-established and powerful synthetic tool for the chemo- and enantioselective functionalization of carbonyl compounds. In the last eight years alone, this field has grown at such an extraordinary pace that it is now recognized as an independent area of synthetic chemistry, where the goal is the preparation of any chiral molecule in an efficient, rapid, and stereoselective manner. This has been made possible by the impressive level of scientific competition and high quality research generated in this area. This Review describes this "Asymmetric Aminocatalysis Gold Rush" and charts the milestones in its development. As in all areas of science, progress depends on human effort.

Asymmetric aminocatalysis--gold rush in organic chemistry.

The detection of explosives is one of the current pressing concerns in global security. In the past few decades, a large number of emissive sensing materials have been developed for the detection of explosives in vapor, solution, and solid states through fluorescence methods. In recent years, great efforts have been devoted to develop new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. This review article starts with a brief introduction on various sensing mechanisms for fluorescence based explosive detection, and then summarizes in an exhaustive and systematic way the state-of-the-art of fluorescent materials for explosive detection with a focus on the research in the recent 5 years. A wide range of fluorescent materials, such as conjugated polymers, small fluorophores, supramolecular systems, bio-inspired materials and aggregation induced emission-active materials, and their sensing performance and sensing mechanism are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed.

Fluorescence based explosive detection: from mechanisms to sensory materials.

Principal changes with respect to the 2004 ECCO guidelines 

Ileocolonoscopy is recommended within the first year after surgery where treatment decisions may be affected (Statement 8C).

Thiopurines are more effective than mesalazine or imidazole antibiotics alone in post-operative prophylaxis (Statement 8F).

### 8.1 Epidemiology of post-operative Crohn's disease

In the natural history of CD, intestinal resection is almost unavoidable since about 80% of patients require surgery at some stage. Surgery is unfortunately not curative as the disease inexorably recurs in many patients. The post-operative recurrence rate varies according to the definition used: clinical, endoscopic, radiological, or surgical. It is lowest when the repeat resection rate is considered, intermediate when clinical indices are used and highest when endoscopy is employed as the diagnostic tool.1–10

Data from endoscopic follow-up of patients after resection of ileo-caecal disease have shown that in the absence of treatment, the post-operative recurrence rate is around 65–90% within 12 months and 80–100% within 3 years of the operation. The clinical recurrence without therapy is about 20–25%/year.1,10 It has been demonstrated that the post-operative clinical course of CD is best predicted by the severity of endoscopic lesions. Symptoms, in fact, appear only when severe lesions are present and it is not uncommon to observe patients with fairly advanced recurrent lesions at endoscopy who remain asymptomatic.1 For these reasons, clinical indices such as the CDAI have low sensitivity at discriminating between patients with or without post-operative recurrence.11

These data mandate strategies aimed at interrupting or delaying the natural course of post-operative recurrence. Several medications have been tried in an attempt to prevent post-operative recurrence, mostly with disappointing results. The aim of this Consensus was therefore critically to evaluate the optimal strategies for the management of post-operative recurrence in CD. Most, if not all, of the evidence available deals with …

/pdf/the-second-european-evidence-based-consensus-on-the-430j75rc37.pdf

The second European evidence-based Consensus on the diagnosis and management of Crohn's disease: Special situations

The design of artificial catalysts able to compete with the catalytic proficiency of enzymes is an intense subject of research. Non-covalent interactions are thought to be involved in several properties of enzymatic catalysis, notably (i) the confinement of the substrates and the active site within a catalytic pocket, (ii) the creation of a hydrophobic pocket in water, (iii) self-replication properties and (iv) allosteric properties. The origins of the enhanced rates and high catalytic selectivities associated with these properties are still a matter of debate. Stabilisation of the transition state and favourable conformations of the active site and the product(s) are probably part of the answer. We present here artificial catalysts and biomacromolecule hybrid catalysts which constitute good models towards the development of truly competitive artificial enzymes.

/pdf/supramolecular-catalysis-part-2-artificial-enzyme-mimics-2h1esy0td8.pdf

Supramolecular catalysis. Part 2: artificial enzyme mimics

There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores. State-of-the-art developments in the fields of polymer and nanomaterial sensors are also examined, and some remaining unsolved challenges in the area of chemosensors are discussed.

/pdf/supramolecular-luminescent-sensors-1rs45r4um4.pdf

Supramolecular Luminescent Sensors

Solutions with as little as 1% enantiomeric excess (ee) of d- or l-phenylalanine are amplified to 90% ee (a 95/5 ratio) by two successive evaporations to precipitate the racemate. Such a process on the prebiotic earth could lead to a mechanism by which meteoritic chiral α-alkyl amino acids could form solutions with high ee values that were needed for the beginning of biology.

https://www.pnas.org/content/pnas/103/35/12979.full.pdf

Amplification of enantiomeric concentrations under credible prebiotic conditions.

Objectives Young children are thought to be a unique subset of pediatric patients with inflammatory bowel disease (IBD). The authors' objective was to evaluate the differences in initial clinical presentation of young and older children with IBD and to determine whether a positive family history of IBD is associated with the age of presentation. Methods The authors reviewed the records of all patients with new diagnoses of Crohn disease (CD) and ulcerative colitis (UC) who presented between July 1996 and July 1999. Initial evaluation included assessment of growth parameters and laboratory values (hemoglobin concentration, platelet count, erythrocyte sedimentation rate, and serum albumin). Inquiry regarding a family history of IBD was made in every patient. Results There were 153 patients with new diagnoses (82 with CD and 71 with UC), with a mean age of 11.9 years (range, 16 months-18 years). The children with CD had a higher sedimentation rate and platelet count and a lower mean hemoglobin concentration and serum albumin at presentation than did children with UC. Body mass index (BMI) was significantly lower in patients with newly diagnosed CD than in those with UC. The only significant laboratory differences between patients younger than 11 years and those 11 years or older was a higher mean platelet count in patients with CD who were younger than 11 years. Of the younger patients with CD, 41.7% had a positive family history of IBD, which was significantly greater that that found in the older patients with CD. Conclusions Except for higher platelet counts, a lower BMI, and a higher frequency of positive family history in young children with CD, there were no significant differences in the presentation of young children with IBD compared with older children.

Age and family history at presentation of pediatric inflammatory bowel disease.

There continues to be a persistent, widespread gender gap in multiple STEM disciplines at all educational and professional levels: from the self-reported interest of preschool aged students in scie

/pdf/addressing-the-stem-gender-gap-by-designing-and-implementing-10f3m1ewbm.pdf

Mindy Levine

Papers

Supramolecular Luminescent Sensors

Amplification of enantiomeric concentrations under credible prebiotic conditions.

Age and family history at presentation of pediatric inflammatory bowel disease.

Addressing the STEM Gender Gap by Designing and Implementing an Educational Outreach Chemistry Camp for Middle School Girls

Enantioselective synthesis and enantiomeric amplification of amino acids under prebiotic conditions.