Non‐racemic chiral boronic esters are recognised as immensely valuable building blocks in modern organic synthesis. Their stereospecific transformation into a variety of functional groups—from amines ...and halides to arenes and alkynes—along with their air and moisture stability, has established them as an important target for asymmetric synthesis. Efforts towards the stereoselective synthesis of secondary and tertiary alkyl boronic esters have spanned over five decades and are underpinned by a wealth of reactivity platforms, drawing on the unique and varied reactivity of boron. This Review summarizes strategies for the asymmetric synthesis of alkyl boronic esters, from the seminal hydroboration methods of H. C. Brown to the current state of the art.
Non‐racemic chiral boronic esters are immensely valuable building blocks in modern organic synthesis. Their stereospecific transformation into a variety of functional groups, along with their air and moisture stability, has established them as an important target for asymmetric synthesis. Methods for their asymmetric synthesis now span a wealth of reactivity platforms.
We report the first enantioselective Rh-catalyzed Markovnikov hydroboration of unactivated terminal alkenes. Using a novel sp2–sp3 hybridized diboron reagent and water as a proton source, a broad ...range of alkenes undergo hydroboration to provide secondary boronic esters with high regio- and enantiocontrol.
Tat-interacting protein of 60 kDa (TIP60) is an essential lysine acetyltransferase implicated in transcription, DNA damage response and apoptosis. TIP60 protein expression is reduced in cancers. In ...cervical cancers, human papillomavirus (HPV) E6 oncogene targets cellular p53, Bak and some of the PDZ domain-containing proteins for proteasome-mediated degradation through E6AP ligase. Recently, E6 oncogene from high-risk and low-risk categories was also shown to target TIP60. However, the molecular mechanisms and whether destabilization of TIP60 contributes to HPV E6-mediated transformation remain unanswered. Our proteomic analyses revealed EDD1 (E3 identified by differential display), an E3 ligase generally overexpressed in cancers as a novel interacting partner of TIP60. By investigating protein turnover and ubiquitination assays, we show that EDD1 negatively regulates TIP60's stability through the proteasome pathway. Strikingly, HPV E6 uses this function of EDD1 to destabilize TIP60. Colony-formation assays and soft agar assays show that gain of function of TIP60 or depletion of EDD1 in HPV-positive cervical cancer cells significantly inhibits cell growth in vitro. This phenotype is strongly supported by the in-vivo studies where re-activation of TIP60 in cervical cancer cells dramatically reduces tumor formation. In summary, we have discovered a novel ligase through which E6 destabilizes TIP60. Currently, in the absence of an effective therapeutic vaccine for malignant cervical cancers, cervical cancer still remains to be a major disease burden. Hence, our studies implying a distinct tumor suppressor role for TIP60 in cervical cancers show that reactivation of TIP60 could be of therapeutic value.
The composite physiologic index (CPI) was derived to represent the extent of fibrosis on high-resolution computed tomography (HRCT), adjusting for emphysema in patients with idiopathic pulmonary ...fibrosis (IPF). We hypothesised that longitudinal change in CPI would better predict mortality than forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC) or diffusing capacity of the lung for carbon monoxide (D(L,CO)) in all patients with IPF, and especially in those with combined pulmonary fibrosis and emphysema (CPFE). Cox proportional hazard models were performed on pulmonary function data from IPF patients at baseline (n = 321), 6 months (n = 211) and 12 months (n = 144). Presence of CPFE was determined by HRCT. A five-point increase in CPI over 12 months predicted subsequent mortality (HR 2.1, p = 0.004). At 12 months, a 10% relative decline in FVC, a 15% relative decline in D(L,CO) or an absolute increase in CPI of five points all discriminated median survival by 2.1 to 2.2 yrs versus patients with lesser change. Half our cohort had CPFE. In patients with moderate/severe emphysema, only a 10% decline in FEV(1) predicted mortality (HR 3.7, p = 0.046). In IPF, a five-point increase in CPI over 12 months predicts mortality similarly to relative declines of 10% in FVC or 15% in D(L,CO). For CPFE patients, change in FEV(1) was the best predictor of mortality.
•We model the efficiency of a nanofluid-based direct absorption solar collector.•We find an approximate analytic solution to the model.•The nanofluid’s temperature rises linearly as it flows through ...the solar collector.•We show the relationship between heat mirrors and solar collector performance.
In this paper we propose an approximate analytic solution to the steady state, three-dimensional model of the efficiency of a nanofluid-based direct absorption parabolic trough solar collector under a turbulent flow regime. The model consists of a system of equations: a partial differential equation describing the conservation of energy, and a radiative transport equation describing the propagation of radiation through the nanofluid. Writing the model in non-dimensional form leads to four controlling non-dimensional numbers, specifically one describing the relative importance of conduction and advection and three representing the heat loss to the surroundings. We use realistic parameter values to reduce the model further and show that two of the non-dimensional groups have a much lesser impact on the performance of the solar collector. Our reduced model suggests that the nanofluid’s temperature rise is linear as it flows through the receiver. The resulting solution is used to investigate the efficiency of the collector and permits optimisation of design parameters such as particle loading, particle type, solar absorption characteristics of the fluid, receiver dimensions, the inlet temperature, and solar concentration ratio. Further analysis of the collector efficiency reveals an inequality that determines whether or not it is reasonable to incorporate a heat-mirror into the solar collector’s design.
The work in this paper concerns the study of conventional and refined heat balance integral methods for a number of phase change problems. These include standard test problems, both with one and two ...phase changes, which have exact solutions that enable us to test the accuracy of the approximate solutions. We also consider situations where no analytical solution is available and compare these to numerical solutions. It is popular to use a quadratic profile as an approximation of the temperature, but we show that a cubic profile, seldom considered in the literature, is far more accurate in most circumstances. In addition, the refined integral method can give greater improvement still, and we develop a variation on this method which turns out to be optimal in some cases. We assess which integral method is better for various problems, showing that it is largely dependent on the specified boundary conditions.
Recently published results suggest that effective vaccines against cervical cancer-associated human papillomavirus (HPV) may become available within the next decade.
To examine the potential health ...and economic effects of an HPV vaccine in a setting of existing screening.
A Markov model was used to estimate the lifetime (age 12-85 years) costs and life expectancy of a hypothetical cohort of women screened for cervical cancer in the United States. Three strategies were compared: (1) vaccination only; (2) conventional cytological screening only; and (3) vaccination followed by screening. Two of the strategies incorporated a vaccine targeted against a defined proportion of high-risk (oncogenic) HPV types. Screening intervals of 1, 2, 3, and 5 years and starting ages for screening of 18, 22, 24, 26, and 30 years were chosen for 2 of the strategies (conventional cytological screening only and vaccination followed by screening).
Incremental cost per life-year gained.
Vaccination only or adding vaccination to screening conducted every 3 and 5 years was not cost-effective. However, at more frequent screening intervals, strategies combining vaccination and screening were preferred. Vaccination plus biennial screening delayed until age 24 years had the most attractive cost-effectiveness ratio (44 889 dollars) compared with screening only beginning at age 18 years and conducted every 3 years. However, the strategy of vaccination with annual screening beginning at age 18 years had the largest overall reduction in cancer incidence and mortality at a cost of 236 250 dollars per life-year gained compared with vaccination and annual screening beginning at age 22 years. The cost-effectiveness of vaccination plus delayed screening was highly sensitive to age of vaccination, duration of vaccine efficacy, and cost of vaccination.
Vaccination for HPV in combination with screening can be a cost-effective health intervention, but it depends on maintaining effectiveness during the ages of peak oncogenic HPV incidence. Identifying the optimal age for vaccination should be a top research priority.
In this paper the two main drawbacks of the heat balance integral methods are examined. Firstly we investigate the choice of approximating function. For a standard polynomial form it is shown that ...combining the heat balance and refined integral methods to determine the power of the highest order term will either lead to the same, or more often, greatly improved accuracy on standard methods. Secondly we examine thermal problems with a time-dependent boundary condition. In doing so we develop a logarithmic approximating function. This new function allows us to model moving peaks in the temperature profile, a feature that previous heat balance methods cannot capture. If the boundary temperature varies so that at some time
t
>
0 it equals the far-field temperature, then standard methods predict that the temperature is everywhere at this constant value. The new method predicts the correct behaviour. It is also shown that this function provides even more accurate results, when coupled with the new CIM, than the polynomial profile. Analysis primarily focuses on a specified constant boundary temperature and is then extended to constant flux, Newton cooling and time dependent boundary conditions.
The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering ...data-and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical Δ(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as αn=11.55±1.25(stat)±0.2(BSR)±0.8(th)×10(-4) fm(3) and βn=3.65∓1.25(stat)±0.2(BSR)∓0.8(th)×10(-4) fm(3), with χ(2)=45.2 for 44 degrees of freedom.
To evaluate the outcomes of excision and primary anastomosis (EPA) for radiation-associated bulbomembranous stenoses using a multi-institutional analysis. The treatment of radiation-associated ...urethral stenosis is typically complex owing to the adverse impact of radiation on adjacent tissue.
An IRB-approved multi-institutional retrospective review was performed on patients who underwent EPA for bulbomembranous urethral stenosis following prostate radiotherapy. Preoperative patient demographics, operative technique, and postoperative outcomes were abstracted from 1/2007–6/2018. Success was defined as voiding per urethra without the need for endoscopic treatment and a minimum follow-up of 12 months.
One hundred and thirty-seven patients from 10 centers met study criteria with a mean age of 69.3 years (50-86), stenosis length of 2.3 cm (1-5) and an 86.9% (119/137) success rate at a mean follow-up 32.3 months (12-118). Univariate Cox regression analysis identified increasing patient age (P = .02), stricture length (P <.0001) and combined modality radiotherapy (P = .004) as factors associated with stricture recurrence while body mass index (P = .79), diabetes (P = .93), smoking (P = .62), failed endoscopic treatment (P = .08) and gracilis muscle use (P = .25) were not. On multivariate analysis, increasing patient age (H.R.1.09, 95%CI 1.01-1.16; P = .02) and stenosis length (H.R.2.62, 95%CI 1.49-4.60; P = .001) remained associated with recurrence. Subsequent artificial urinary sphincter was performed in 30 men (21.9%), of which 25 required a transcorporal cuff and 5 developed cuff erosion.
EPA for radiation-associated urethral stenosis effectively provides unobstructed instrumentation-free voiding. However, increasing stenosis length and age are independently associated with surgical failure. Patients should be counseled that further surgery for incontinence may be necessary.
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