Dipyrazolylphosphanes in Condensation and P–N/P–P Bond Metathesis Reactions

Phosphorus plays a crucial role in modern p-block chemistry.1 One reason for that is the diagonal relationship between phosphorus and carbon.2 Comparable to carbon and its chemistry, phosphorus tends to form homoatomic bonds, which is explainable by the relatively high P–P single bond energy (ca. 200 kJ/mol).3 Thus, a plethora of poly-phosphorus compounds are reported in the last decades comprising of fascinating bonding motifs4 and interesting applications in coordination5-7 and synthetic8-11 chemistry, as well as in ligand design.12,13 A crucial point in the chemistry of polyphosphanes is of course the formation of P–P bonds. Numerous synthetic procedures are established and reviewed including salt metathesis,4a,14 dehalosilylation15 and dehalostannylation16 reactions, base promoted dehydrohalogenation reactions17 and dehydrogenative coupling reactions mediated by main group compounds18 or catalysis by transition metals.5,19 Moreover, dialkylamino-substituted phosphanes are used in condensation reactions to form P–P bonds since the early 1960’s. Yet these reactions need elevated temperatures, somewhat limiting the formation of polyphosphorus compounds as stated by the few examples reported.17d,20 The application of pyrazolyl-substituted phosphanes in P–P bond formation reactions is a relatively young field of research.21 Their synthesis and general chemical behavior as well as advantages in comparison to dialkylamino-substituted phosphanes is discussed in the following chapter

Segmentation and wake removal of seafaring vessels in optical satellite images

ABSTRACT This paper aims at the segmentation of seafaring vessels in optical satellite images, which allows an accurate length estimation. In maritime situation awareness, vessel length is an important parameter to classify a vessel. The proposed segmentation system consists of robust foreground-background separation, wake detection and ship-wake separation, simultaneous position and profile clustering and a special module for small vessel segmentation. We compared our system with a baseline implementation on 53 vessels that were observed with GeoEye-1. The results show that the relative L1 error in the length estimation is reduced from 3.9 to 0.5, which is an improvement of 87%. We learned that the wake removal is an important element for the accurate segmentation and length estimation of ships

Follow-up of patients with curatively resected colorectal cancer: a practice guideline

BACKGROUND: A systematic review was conducted to evaluate the literature regarding the impact of follow-up on colorectal cancer patient survival and, in a second phase, recommendations were developed. METHODS: The MEDLINE, CANCERLIT, and Cochrane Library databases, and abstracts published in the 1997 to 2002 proceedings of the annual meeting of the American Society of Clinical Oncology were systematically searched for evidence. Study selection was limited to randomized trials and meta-analyses that examined different programs of follow-up after curative resection of colorectal cancer where five-year overall survival was reported. External review by Ontario practitioners was obtained through a mailed survey. Final approval of the practice guideline report was obtained from the Practice Guidelines Coordinating Committee. RESULTS: Six randomized trials and two published meta-analyses of follow-up were obtained. Of six randomized trials comparing one follow-up program to a more intense program, only two individual trials detected a statistically significant survival benefit favouring the more intense follow-up program. Pooling of all six randomized trials demonstrated a significant improvement in survival favouring more intense follow-up (Relative Risk Ratio 0.80 (95%CI, 0.70 to 0.91; p = 0.0008). Although the rate of recurrence was similar in both of the follow-up groups compared, asymptomatic recurrences and re-operations for cure of recurrences were more common in patients with more intensive follow-up. Trials including CEA monitoring and liver imaging also had significant results, whereas trials not including these tests did not. CONCLUSION: Follow-up programs for patients with curatively resected colorectal cancer do improve survival. These follow-up programs include frequent visits and performance of blood CEA, chest x-rays, liver imaging and colonoscopy, however, it is not clear which tests or frequency of visits is optimal. There is a suggestion that improved survival is due to diagnosis of recurrence at an earlier, asymptomatic stage which allows for more curative resection of recurrence. Based on this evidence and consideration of the biology of colorectal cancer and present practices, a guideline was developed. Patients should be made aware of the risk of disease recurrence or second bowel cancer, the potential benefits of follow-up and the uncertainties requiring further clinical trials. For patients at high-risk of recurrence (stages IIb and III) clinical assessment is recommended when symptoms occur or at least every 6 months the first 3 years and yearly for at least 5 years. At the time of those visits, patients may have blood CEA, chest x-ray and liver imaging. For patients at lower risk of recurrence (stages I and Ia) or those with co-morbidities impairing future surgery, only visits yearly or when symptoms occur. All patients should have a colonoscopy before or within 6 months of initial surgery, and repeated yearly if villous or tubular adenomas >1 cm are found; otherwise repeat every 3 to 5 years. All patients having recurrences should be assessed by a multidisciplinary team in a cancer centre

Dipyrazolylphosphanes in Condensation and P–N/P–P Bond Metathesis Reactions

Phosphorus plays a crucial role in modern p-block chemistry.1 One reason for that is the diagonal relationship between phosphorus and carbon.2 Comparable to carbon and its chemistry, phosphorus tends to form homoatomic bonds, which is explainable by the relatively high P–P single bond energy (ca. 200 kJ/mol).3 Thus, a plethora of poly-phosphorus compounds are reported in the last decades comprising of fascinating bonding motifs4 and interesting applications in coordination5-7 and synthetic8-11 chemistry, as well as in ligand design.12,13 A crucial point in the chemistry of polyphosphanes is of course the formation of P–P bonds. Numerous synthetic procedures are established and reviewed including salt metathesis,4a,14 dehalosilylation15 and dehalostannylation16 reactions, base promoted dehydrohalogenation reactions17 and dehydrogenative coupling reactions mediated by main group compounds18 or catalysis by transition metals.5,19 Moreover, dialkylamino-substituted phosphanes are used in condensation reactions to form P–P bonds since the early 1960’s. Yet these reactions need elevated temperatures, somewhat limiting the formation of polyphosphorus compounds as stated by the few examples reported.17d,20 The application of pyrazolyl-substituted phosphanes in P–P bond formation reactions is a relatively young field of research.21 Their synthesis and general chemical behavior as well as advantages in comparison to dialkylamino-substituted phosphanes is discussed in the following chapter

Dipyrazolylphosphanes in Condensation and P–N/P–P Bond Metathesis Reactions

Phosphorus plays a crucial role in modern p-block chemistry.1 One reason for that is the diagonal relationship between phosphorus and carbon.2 Comparable to carbon and its chemistry, phosphorus tends to form homoatomic bonds, which is explainable by the relatively high P–P single bond energy (ca. 200 kJ/mol).3 Thus, a plethora of poly-phosphorus compounds are reported in the last decades comprising of fascinating bonding motifs4 and interesting applications in coordination5-7 and synthetic8-11 chemistry, as well as in ligand design.12,13 A crucial point in the chemistry of polyphosphanes is of course the formation of P–P bonds. Numerous synthetic procedures are established and reviewed including salt metathesis,4a,14 dehalosilylation15 and dehalostannylation16 reactions, base promoted dehydrohalogenation reactions17 and dehydrogenative coupling reactions mediated by main group compounds18 or catalysis by transition metals.5,19 Moreover, dialkylamino-substituted phosphanes are used in condensation reactions to form P–P bonds since the early 1960’s. Yet these reactions need elevated temperatures, somewhat limiting the formation of polyphosphorus compounds as stated by the few examples reported.17d,20 The application of pyrazolyl-substituted phosphanes in P–P bond formation reactions is a relatively young field of research.21 Their synthesis and general chemical behavior as well as advantages in comparison to dialkylamino-substituted phosphanes is discussed in the following chapter

Contour dynamics for vortex-induced advection

iv+146hlm.;24c

Factors associated with poor satisfaction with treatment and trial discontinuation in chronic schizophrenia

Introduction  Despite consistently high discontinuation rates due to withdrawal of consent (WOC) and insufficient therapeutic effect (ITE) in schizophrenia trials, insight into the underlying factors contributing to poor satisfaction with treatment and dropout is limited. A better understanding of these factors could help to improve trial design and completion rates.  Methods  Using data from 1,136 trial participants with schizophrenia or schizoaffective disorder, we explored associations between predictor variables with (1) dropout due to WOC and ITE and (2) satisfaction with treatment among patients and investigators by means of hierarchic multiple regression analyses.  Results  ITE was associated with poor clinical improvement, poor investigator satisfaction with treatment, and poor patient insight into their own disease, whereas WOC only showed a meaningful association with poor patient satisfaction with treatment. Investigator satisfaction with treatment appeared most strongly associated with Positive and Negative Syndrome Scale (PANSS) positive factor endpoint scores, whereas patient satisfaction with treatment was best predicted by the endpoint score on the PANSS emotional distress factor. The occurrence of severe side effects showed no meaningful association to satisfaction with treatment among investigators and patients, and neither did a patient's experienced psychopathology, nor their self-rating of functional impairment.  Conclusions  Whereas trial discontinuation due to ITE is associated with poor treatment effectiveness, a patient's decision to withdraw from an antipsychotic trial remains unpredictable and may occur even when the investigator observes a global clinical improvement and is satisfied with the treatment

Cationic 5-phosphonio-substituted N-heterocyclic carbenes

2-Phosphanyl-substituted imidazolium salts 2-PR2(4,5-Cl-Im)[OTf] (9a,b[OTf]) (4,5-Cl-Im = 4,5-dichloro-1,3-bis(2,6-di-isopropylphenyl)-imidazolium) (a: R = Cy, b: R = Ph) are prepared from the reaction of R2PCl (R = Cy, Ph) with NHC 8 (4,5-dichloro-1,3-bis(2,6-di-isopropylphenyl)-imidazolin-2-ylidene) in the presence of Me3SiOTf. 5-Phospanyl-substituted imidazolium salts 5-PR2(2,4-Cl-Im)[OTf] (10a,b[OTf]) are obtained in quantitative yield when a slight excess of the NHC 8 is used. 5-Phosphonio-substituted imidazolium salts 5-PR2Me(2,4-Cl-Im)[OTf]2 (14a,b[OTf]2) and 5-PR2F(2,4-Cl-Im)[OTf]2 (16a,b[OTf]2) result from methylation reaction or oxidation of 10a,b[OTf] with XeF2 and subsequent fluoride abstraction. According to our quantum chemical studies the Cl1 atom at the 2-position at the imidazolium ring of dication 14b2+ carries a slightly positive charge and is therefore accessible for nucleophilic attack. Accordingly, the reaction of 14a,b[OTf]2 and 16a,b[OTf]2 with R3P (R = Cy, Ph) affords cationic 5-phosphonio-substituted NHCs 5-PR2Me(4-Cl-NHC)[OTf] (17a,b[OTf]) and 5-PR2F(4-Cl-NHC)[OTf] (18a,b[OTf]) via a SN2(Cl)-type reaction. A series of transition metal complexes such as [AuCl(5-PPh2Me(4-Cl-NHC))][OTf] (19[OTf]), [CuBr(5-PPh2Me(4-Cl-NHC))][OTf] (20[OTf]), [AuCl(5-PPh2F(4-Cl-NHC))[OTf] (21[OTf]) and [RhCl(cod)(5-PPh2Me(4-Cl-NHC))][OTf] (23[OTf]) are prepared to prove the coordination abilities of carbenes 17b[OTf] and 18b[OTf]. The isolation of a rare example of a tricationic bis-carbene silver complex [Ag(5-PPh2Me(4-Cl-NHC))2][OTf]3 (22[OTf]3) is achieved by reacting 14b[OTf] with Cy3P in the presence of AgOTf. NHC 17b[OTf] represents a very effective dehydrocoupling reagent for secondary (R2PH, R = Ph, Cy, iBu) and primary (RPH2, R = Ph, Cy) phosphanes to give diphosphanes of type R4P2 (R = Ph, Cy, iBu) and oligophosphanes R4P4, R5P5 (R = Ph, Cy), respectively. Methylation of 17b+ and subsequent deprotonation reaction with LDA affords the cationic NHO (N-heterocyclic olefin) 35+ of which the gold complex 36+ is readily accessible via the reaction with AuCl(tht)