Singlet fission promises to surpass the Shockley-Queisser limit for single-junction solar cell efficiency through the production of two electron-hole pairs per incident photon. However, this promise ...has not been fulfilled because singlet fission produces two low-energy triplet excitons that have been unexpectedly difficult to dissociate into free charges. To understand this phenomenon, we study charge separation from triplet excitons in polycrystalline pentacene using an electrochemical series of 12 different guest electron-acceptor molecules with varied reduction potentials. We observe separate optima in the charge yield as a function of driving force for singlet and triplet excitons, including inverted regimes for the dissociation of both states. Molecular acceptors can thus provide a strategic advantage to singlet fission solar cells by suppressing singlet dissociation at optimal driving forces for triplet dissociation. However, even at the optimal driving force, the rate constant for charge transfer from the triplet state is surprisingly small, ~10
s
, presenting a previously unidentified obstacle to the design of efficient singlet fission solar cells.
Singlet fission (SF) has the potential to bypass the Shockley–Queisser limit for solar cell efficiency through the production of two electron–hole pairs per photon. However, in polycrystalline ...pentacene this goal is hindered by slow charge transfer from triplets (≤107 s–1) after SF. In this paper we show that slow charge transfer is an intrinsic property of triplet states in this material and most likely not connected with the triplet pair states that may result from singlet fission. We compare two perylene diimide/pentacene charge transfer systems that differ only by triplet generation mechanism: SF versus intersystem crossing (ISC), sensitized by using a soluble lead phthalocyanine derivative. We use time-resolved microwave conductivity (TRMC) to measure the charge yield in each system and transient absorption (TA) to follow the triplet population dynamics. These experiments are described by a single global kinetic model, with most of its parameters fixed via control experiments. While we observe modest differences in the charge-transfer rate constants between each sample, 4–10× as a function of triplet generation mechanism, all samples remain far below the predicted diffusion-limited rate constant of 107–108 s–1.
To describe a novel laminin β-2 (LAMB2) mutation associated with nephrotic syndrome and severe retinal disease without microcoria in a large, multigenerational family with Pierson syndrome.
...Retrospective chart review and prospective family examination.
An extended consanguineous family of 52 members.
The eyes, urine, and serum DNA were evaluated in all family members after discovering 2 patients, both younger than 10 years, with bilateral retinal detachments and concurrent renal dysfunction. Linkage analysis was performed in the 9 living affected individuals, 7 using the Illumina Human Hap370 Duo Bead Array (Illumina, San Diego, CA) and 2 using GeneChip 10K (Affymetrix, Santa Clara, CA) mapping arrays.
The prevalence and severity of ocular and kidney involvement and genetic findings.
Eleven affected family members were identified (9 living), all manifesting chronic kidney disease and bilateral chorioretinal pigmentary changes, with or without retinal detachments, but without microcoria or neurodevelopmental deficits, segregating in an autosomal recessive pattern. The causative gene was localized to a 9-Mb region on chromosome 3. Comprehensive gene sequencing revealed a novel LAMB2 variant (c.440A → G; His147R) that was homozygous in the 9 living, affected family members, observed at a frequency of 2.1% in the Old Order Mennonite population, and absent in 91 non-Mennonite controls. The mutation is located in a highly conserved site in the N-terminal domain VI of LAMB2.
This study describes a novel mutation of LAMB2 and further expands the spectrum of eye and renal manifestations associated with defects in the laminin β-2 chain.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Background/AimsThere are approximately 150,000 new hormone-sensitive breast cancer cases in the U.S. each year. Numerous studies have shown that adjuvant hormonal therapy (AHT) dramatically reduces ...breast cancer recurrence and mortality. Daily treatment for 5 years is the recommended therapy among ER+ women. Yet, reports of under-utilization are alarming, ranging from 30% to more than 50%.MethodsWe examined under-utilization of AHT among members of Kaiser Permanente Southern California (KPSC), a nonprofit prepaid managed care organization dedicated to providing evidence-based medicine. KPSC serves 3.3 million socioeconomically diverse members broadly representative of the racial/ethnic groups living in southern California. Subjects were members of the health plan for one or more years and had comprehensive medical and pharmacy benefits. We identified 10,827 women diagnosed with breast cancer between 2000 and 2007 from the health plan's SEER-affiliated cancer registry who were eligible for AHT. We used automated pharmacy prescription records to describe uptake and utilization of AHT (primarily tamoxifen (Tam) and aromatase inhibitors (AI)) over the 5 years of recommended therapy.ResultsIn this insured population, we found 14% of eligible breast cancer survivors did not begin AHT (1516/10,827). Of those who started AHT, over 30% had sub-optimal adherence defined as a medication possession ratio <80%. Discontinuation of AHT, defined as greater than 90 days without medication, began in year 1 (7%) and reached 22% and 25% by the end of years 4 and 5, respectively.DiscussionMonitoring and intervention for improving adherence to AHT needs to begin by one year after breast cancer diagnosis and continue across the 5 years of recommended therapy in order to ensure women receive optimal benefit from this lifesaving treatment.
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