Molecular Structure Tailoring of Organic Spacers for High‑Performance Ruddlesden–Popper Perovskite Solar Cells

Layer-structured Ruddlesden–Popper(RP)perovskites(RPPs)with decent stability have captured the imagination of the photovoltaic research community and bring hope for boosting the development of perovskite solar cell(PSC)technology.However,two-dimensional(2D)or quasi-2D RP PSCs are encountered with some challenges of the large exciton binding energy,blocked charge transport and poor film quality,which restrict their photovoltaic performance.Fortunately,these issues can be readily resolved by rationally designing spacer cations of RPPs.This review mainly focuses on how to design the molecular structures of organic spacers and aims to endow RPPs with outstanding photovoltaic applications.We firstly elucidated the important roles of organic spacers in impacting crystallization kinetics,charge transporting ability and stability of RPPs.Then we brought three aspects to attention for designing organic spacers.Finally,we presented the specific molecular structure design strategies for organic spacers of RPPs aiming to improve photovoltaic performance of RP PSCs.These proposed strategies in this review will provide new avenues to develop novel organic spacers for RPPs and advance the development of RPP photovoltaic technology for future applications.

Recent Progress of Layered Perovskite Solar Cells Incorporating Aromatic Spacers

Layered two dimensional(2D) or quasi-2D perovskites are emerging photovoltaic materials due to their superior environment and structure stability in comparison with their 3D counterparts. The typical 2D perovskites can be obtained by cutting 3D perovskites along < 100 > orientation by incorporation of bulky organic spacers, which play a key role in the performance of 2D perovskite solar cells(PSCs). Compared with aliphatic spacers, aromatic spacers with high dielectric constant have the potential to decrease the dielectric and quantum confinement effect of 2D perovskites, promote efficient charge transport and reduce the exciton binding energy, all of which are beneficial for the photovoltaic performance of 2D PSCs. In this review, we aim to provide useful guidelines for the design of aromatic spacers for 2D perovskites. We systematically reviewed the recent progress of aromatic spacers used in 2D PSCs. Finally, we propose the possible design strategies for aromatic spacers that may lead to more efficient and stable 2D PSCs.

Boosting MA-based two-dimensional Ruddlesden-Popper perovskite solar cells by incorporating a binary spacer

Two-dimensional Ruddlesden-Popper(2DRP)perovskite exhibits excellent stability in perovskite solar cells(PSCs)due to introducing hydrophobic long-chain organic spacers.However,the poor charge transporting property of bulky organic cation spacers limits the performance of 2DRP PSCs.Inspired by the Asite cation alloying strategy in 3D perovskites,2DRP perovskites with a binary spacer can promote charge transporting compared to the unary spacer counterparts.Herein,the superior MA-based 2DRP perovskite films with a binary spacer,including 3-guanidinopropanoic acid(GPA)and 4-fluorophenethylamine(FPEA)are realized.These films(GPA_(0.85)FPEA_(0.15))_(2)MA_(4)Pb_5I_(16)show good morphology,large grain size,decreased trap state density,and preferential orientation of the as-prepared film.Accordingly,the present 2DRP-based PSC with the binary spacer achieves a remarkable efficiency of 18.37%with a V_(OC)of1.15 V,a J_(SC)of 20.13 mA cm^(-2),and an FF of 79.23%.To our knowledge,the PCE value should be the highest for binary spacer MA-based 2DRP(n≤5)PSCs to date.Importantly,owing to the hydrophobic fluorine group of FPEA and the enhanced interlayer interaction by FPEA,the unencapsulated 2DRP PSCs based on binary spacers exhibit much excellent humidity stability and thermal stability than the unary spacer counterparts.

Synthesis and Properties of Gemini Cationic Surfactants with Amide Spacers

Four gemini cationic surfactants {N,N′-di[2-(lauryldimethylamino)acetyl]polymethylenediamine dichloride, LAA-s-LAA, s=2,3,4,6} were synthesized by using four bis(α-chloroacetamide)s and N,N-dimethyllaurylamine, respectively. The molecular structures were characterized by means of IR, ~ 1H NMR, \{~ ~13 C NMR\} and MS, and the behavior of their aqueous solutions was studied. The critical micell concentrations(CMC) of LAA-s-LAA were one order of magnitude lower than that of dodecyltrimethyl ammonium chloride(DTAC). With the change of the length of spacer chain(s), their CMC values change, and CMC reaches the top value at s=4.

Current role of spacers for prostate cancer radiotherapy

Radiotherapy is an established curative treatment method for prostate cancer. Optimal tumor control rates can only be achieved with high local doses,associated with a considerable risk of rectal toxicity. Apart from already widely adapted technical advances,as intensitymodulated radiation therapy,the application of spacers placed between the prostate and rectum has been increasingly used in the last years. Biodegradable spacers,including hydrogel,hyaluronic acid,collagen or an implantable balloon,can be injected or inserted in a short procedure under transrectal ultrasound guidance via a transperineal approach. A distance of about 1.0-1.5 cm is usually achieved between the rectum and prostate,excluding the rectal wall from the high isodoses. Several studies have shown well tolerated injection procedures and treatments. Apart from considerable reduction of rectal irradiation,a prospective randomized trial demonstrated a reduction of rectal toxicity after hydrogel injection in men undergoing prostate image-guided intensity-modulated radiation therapy. The results are encouraging for continuing evaluation in dose escalation,hypofractionation,stereotactic radiotherapy or re-irradiation trials in the future.

Effects of Flexible Conjugation-Break Spacers of Non-Conjugated Polymer Acceptors on Photovoltaic and Mechanical Properties of All-Polymer Solar Cells

All-polymer solar cells(all-PSCs)possess attractive merits including superior thermal stability and mechanical flexibility for large-area roll-to-roll processing.Introducing flexible conjugation-break spacers(FCBSs)into backbones of polymer donor(P_(D))or polymer acceptor(P_(A))has been demonstrated as an efficient approach to enhance both the photovoltaic(PV)and mechanical properties of the all-PSCs.However,length dependency of FCBS on certain all-PSC related properties has not been systematically explored.In this regard,we report a series of new non-conjugated P_(A)s by incorporating FCBS with various lengths(2,4,and 8 carbon atoms in thioalkyl segments).Unlike com-mon studies on so-called side-chain engineering,where longer side chains would lead to better solubility of those resulting polymers,in this work,we observe that the solubilities and the resulting photovoltaic/mechanical properties are optimized by a proper FCBS length(i.e.,C2)in P_(A) named PYTS-C2.Its all-PSC achieves a high efficiency of 11.37%,and excellent mechanical robustness with a crack onset strain of 12.39%,significantly superior to those of the other P_(A)s.These results firstly demonstrate the effects of FCBS lengths on the PV performance and mechanical properties of the all-PSCs,providing an effective strategy to fine-tune the structures of P_(A)s for highly efficient and mechanically robust PSCs.

Phylogenetic Relationships of <i>Termitomyces aurantiacus</i>Inferred from Internal Transcribed Spacers DNA Sequences

Fungus-growing termites cultivate species of the mutualistic basidiomycete genus Termitomyces on a substrate called the fungal comb. Identification of fungal species based on morphological features is complicated, tedious, and prone to errors. As an alternative, nuclear ribosomal DNA sequences consisting of the internal transcribed spacers (ITS1 and ITS2) and 5.8S rDNA were used to identify Malaysian isolates of Termitomyces sp. The morphological characteristics and molecular data indicate that Malaysian Termitomyces isolated is clearly monophyletic and belongs to the Tricholomataceae family. The Malaysian isolates analyzed in this study represent the termite fungus species called T. aurantiacus.

Improved patient reported outcomes with functional articulating spacers in two-stage revision of the infected hip

BACKGROUND Two-stage revision arthroplasty with an antibiotic-loaded spacer is the treatment of choice in chronically infected total hip arthroplasties.Interval spacers can be functional articulating or prefabricated.Functional results of these spacers have scarcely been reported.AIM To compare retrospectively the patient reported outcome and infection eradication rate after two-stage revision arthroplasty of the hip with the use of a functional articulating or prefabricated spacer.METHODS All patients with two-stage revision of a hip prosthesis at our hospital between 2003 and 2016 were included in this retrospective cohort study.Patients were divided into two groups;patients treated with a functional articulating spacer or with a prefabricated spacer.Patients completed the Hip Osteoarthritis Outcome Score and the EQ-5D-3L(EQ-5D)and the EQ-5D quality of life thermometer(EQVAS)scores.Primary outcomes were patient reported outcome and infection eradication after two-stage revision.The results of both groups were compared to the patient acceptable symptom state for primary arthroplasty of the hip.Secondary outcomes were complications during spacer treatment and at final follow-up.Descriptive statistics,mean and range are used to represent the demographics of the patients.For numerical variables,students’t-tests were used to assess the level of significance for differences between the groups,with 95%confidence intervals;for binary outcome,we used Fisher’s exact test.RESULTS We consecutively treated 55 patients with a prefabricated spacer and 15 patients with a functional articulating spacer of the hip.The infection eradication rates for functional articulating and prefabricated spacers were 93%and 78%,respectively(P>0.05).With respect to the functional outcome,the Hip Osteoarthritis Outcome Score(HOOS)and its subscores(all P<0.01),the EQ-5D(P<0.01)and the EQVAS scores(P<0.05)were all significantly better for patients successfully treated with a functional articulating spacer.More patients in the functional articulating spacer group reached the patient acceptable symptom state for the HOOS pain,HOOS quality of life and EQ-VAS.The number of patients with a spacer dislocation was not significantly different for the functional articulating or prefabricated spacer group(P>0.05).However,the number of dislocations per patient experiencing a dislocation was significantly higher for patients with a prefabricated spacer(P<0.01).CONCLUSION Functional articulating spacers lead to improved patient reported functional outcome and less perioperative complications after two-stage revision arthroplasty of an infected total hip prosthesis,while maintaining a similar infection eradication rate compared to prefabricated spacers.

THE EFFECT OF SUBSTITUENT ON THE THERMAL PROPERTIES OF POLYESTERS CONSISTING OF AROMATIC TYPE SCHIFF BASE MESOGENIC UNITS AND POLYMETHYLENE SPACERS

Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2' positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.

DNA Barcoding of <i>Ricinus communis</i>from Different Geographical Origin by Using Chloroplast <i>matK</i>and Internal Transcribed Spacers

Ricinus communis have attracted considerable attention because of its specific industrial and pharmacological activities. DNA barcodes can be used as reliable tools to facilitate the identification of medicinal plants for the safe use, quality control and forensic investigation. In this study, the differential identification of eight accessions of R. com-munis was investigated through DNA sequence analysis of two candidate DNA barcodes. The nucleotide sequence of internal transcribed spacers (ITS2) and chloroplast maturase gene (matK) have been determined to construct the phylogenetic tree. The phylogenetic relationships of accessions based on the nrITS2 region and partial matK region showed that all accessions in this study were related to three geographical origins. Based on sequence align-ment and phylogenetic analyses we concluded that the ITS2 sequences can distinguish R. communis accessions from different geographical distributions.

Score based assessment of implant-related post fusion MRI artifacts focused on different interbody disc spacers: An <i>in vitro</i>study

Interbody disc spacers for anterior spine fusion are made of different materials, such as titanium alloys or carbon fiber reinforced polymers (CFRP). Implant-related susceptibility artifacts can decrease the quality of MRI scans. This cadaveric study aimed to demonstrate the extent that implant-related MRI artifacting affects the post fusion differentiation of the spinal canal (SC) and intervertebral disc space (IDS). In 6 cadaveric porcine spines, we evaluated the post-im- plantation MRI scans of a titanium and CFRP spacer that differed in shape and surface qualities. A spacer made of human cortical bone was used as a control. A defined evaluation unit was divided into regions of interest (ROI) to characterize the SC and IDS. Considering 15 different MRI sequences read independently by an interobserver-validated team of specialists artifact-affected image quality of the median MRI slice was rated on a modified score of 0-1-2-3. A maximum score of 15 points for the SC and 9 points for the IDS (100%) was possible. Turbo spin echo sequences produced the best scores for both spacers and the control. Only the control achieved a score of 100%. For the IDS the titanium and CFRP spacer maximally scored 0% and 74%, for the SC 80% and 99%, respectively. By using favored T1 TSE sequences the CFRP-spacer represented clear advantages in post fusion spinal imaging. Independent of artifact dimensions the used scoring system allowed us to create an implant-related ranking of MRI scan quality in reference to the bone control.

Implant-related MRI artifacts of determined interbody test spacers: artifact calculations due to implant parameters in a porcine spine model

Aim: Intervertebral spacers for anterior spine fusion are made of different materials, which can affect the post-fusion MRI scans. Suscep- tibility artifacts specially for implants made of titanium alloys can decrease the image quality. This study focused on the influence of deter-mined implant parameters like shape and implant volume in MRI artifacting independent from se-lected MRI-sequences. Methods: In this study the post-implantation MRI scans of determined cuboids and cylinders were evaluated. All in-terbody test implants were made of titanium alloys. MRI scans were carried out by using T1 TSE sequences. The total artifact volume (TAV) of all examined implants were calculated for sta-tistical t-test correlation and implant volume (IV)/TAV-relation. Results: Considering all ex-amined test implants with an increasing implant size the TAV became significant larger (p<0,001) with simultaneous reduction of the respective IV/TAV-relation. According to an intergroup TAV- correlation for cylinders and cuboids with an equivalent implant volume the cylindric test im-plants demonstrated a significant smaller arti-fact range (p<0,05). Conclusions: Based on these results the MRI artifacts of larger test im-plants were more limited to the to the implant’s direct surroundings. In this connection for im- plants with identical material volumes a cylin- dric shape demonstrated more advantages con- sidering MRI artifacting than cubic forms.

Imaging characteristics of metallic interbody spacers: in vitro score evaluation of susceptibility artifacts considering different MRI sequences

Aim: Intervertebral spacers for anterior spine fusion are made of different materials, such as titanium, carbon or cobalt-chrome, which can affect the post- fusion MRI scans. Implant-related susceptibility artifacts can decrease the quality of MRI scans, thwar- ting proper evaluation. This cadaver study aimed to demonstrate the extent that implant-related MRI artifacting affects the post-fusion evaluation of intervertebral spacers. Methods: In a cadaveric porcine spine, we evaluated the post-implantation MRI scans of 2 metallic intervertebral spacers (TiAL6V4, CoCrMo) that differed in shape, material, surface qualities and implantation technique. A spacer made of human cortical bone was used as a control. The median sagittal MRI slice was divided into 12 regions of interest (ROI). Results: No significant differences were found on 15 different MRI sequences read independently by an interobserver-validated team of specialists (P>0.05). Artifact-affected image quality was rated on a score of 0-1-2. A maximum score of 24 points (100%) was possible. Turbo spin echo sequences produced the best scores for all spacers and the control. Only the control achieved a score of 100%. The titanium and cobalt-chrome spacers scored 62.5% and 50%, respectively. Conclusions: Our scoring system allowed us to create an implant-related rank- ing of MRI scan quality in reference to the control that was independent of artifact dimensions. Even with turbo spin echo sequences, the susceptibility artifacts produced by the metallic spacers showed a high degree of variability. Despite optimum sequen- cing, implant design and material are relevant factors in MRI artifacting.

CRYSTALLINE MORPHOLOGY IN A SERIES OF CH_(3)-SUBSTITUTED THERMOTROPIC AROMATIC POLYESTERS WITH EVEN AND ODD FLEXIBLE SPACERS

Crystalline morphology in a series of CH_(3)-substituted main chain thermotropic aromatic polyesters with even and odd numbered methylene spacers has been studied by polarizing optical microscopy(POM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).On crystallization from solution evaporation spherulites of radial structure were observed in the polymers with even numbered spacers,but spherulites with concentric rings form in the polymer with odd numbered spacers.Both spherulites have a lamellar structure,which is about 10 nm in thickness.On crystallization from nematic glassy state spherulites can not be grown;lamellar structure was only observed around disclinations in a specimen during crystallization.Ln the case of crystallization from nematic melt two types of spherulites can be observed far the sample with even numbered spacers.For the sample with add numbered spacers spherulites can not be formed,but only irregular crystallites.

Effect of Weft Binding Structure on Compression Properties of Three-Dimensional Woven Spacer Fabrics and Composites

With the wide use of three-dimensional woven spacer composites(3DWSCs),the market expects greater mechanical properties from this material.By changing the weft fastening method of the traditional I-shape pile yarns,we designed three-dimensional woven spacer fabrics(3DWSFs)and 3DWSCs with the weft V-shape to improve the compression performance of traditional 3DWSFs.The effects of weft binding structures,V-pile densities,and V-shaped angle were investigated in this paper.It is found that the compression resistance of 3DWSFs with the weft V-shape is improved compared to that with the weft I-shape,the fabric height recovery rate is as high as 95.7%,and the average elastic recovery rate is 59.39%.When the interlayer pile yarn density is the same,the weft V-shaped and weft I-shaped 3DWSCs have similar flatwise pressure and edgewise pressure performance.The compression properties of the composite improve as the density of the V-pile yarns increases.The flatwise compression load decreases as the V-shaped angle decreases.When the V-shaped angle is 28°and 42°,the latitudinal V-shaped 3DWSCs perform exceptionally well in terms of anti-compression cushioning.The V-shaped weft binding method offers a novel approach to structural design of 3DWSCs.

INFLUENCE OF ELECTRICAL AND STRUCTURAL PARAMETERS ON THE PERFORMANCE OF THE SPACERS IN HOPFED

The HOPping Field Emission Display （HOPFED） is a new architecture for field emission displays. The main difference between a conventional Field Emission Display （FED） device and a ItOPFED lies in the spacer structure. In a HOPFED, two dielectric plates, named hop and flu spacer, are sandwiched between the emitter and the front plate. The objective of this spacer structure is to improve the performance oF a FED substantially with notable contrast, color purity and luminance uniformity. In order to optimize the structure of the device and to make the electron spot on the screen match the requirement of the phosphor dot dimension, the influence of electrical and structural parameters of the device on the electron spot profile was studied by numerical simulation in this paper. Monte Carlo method was employed to calculate the potential distribution inside hop and flu spacers due to secondary electrons mechanism plays an important role in HOPFED. The results indicated that the potential distribution in the spacers and spot profile depended strongly on the hop voltage, anode voltage and spacer＇s layout. This study may provide a useful theoretical support for optimizing the structure in HOPFED.

PREPARATION OF LIQUID CRYSTALLINE COPOLYESTERS WITH SPACERS BASED ON BISPHENOL-A,BISPHENOL-S OR POLYSULFONE BY DIRECT POLYCONDENSATION

Four series of copolyesters were synthesized by direct polycondonsation reaction between aromatic dicarboxylic acids and bisphenols by using tosyi chloride and N, N-dimethylformamide ( DMF ) in pyridine under mild conditions. The electron-rich hydroxyl groups of bisphenols favoured the polycondensation reaction and the order of relative reactivities of bisphenols is as follow:bisphenoI-A> hydroquinone ～ bisphenol-S> chlorohydroquinone. The mesomorphic properties of copolyesters were examined by birefringence under polarizing microscope, melt transparency. DSC and X-ray diffraction. The minimum molar fraction of mesogenic units needed for the appearance of liquid crystallinity is not higher than 0. 1 despite of the different varieties and lengths of the spacers studied.

Characterization of Fusarium Oxysporum Isolates Obtained from Wax Gourd and Chieh-qua in China by Pathogenicity, RAMs and Sequence Analysis of the rDNA Internal Transcribed Spacers (ITS1 and ITS2)

Wax gourd (Benincasa hispida Thumb. Cogn) is called white gourd, winter melon, Chinese preserving melon, Chinese squash, and don kwa. It has been cultivated in China for over 2 300 years. It probably

直流电压下GIS盆式绝缘子表面电荷及电场分布特性仿真研究

GIS中盆式绝缘子表面在外施直流电压时会积聚大量电荷使得沿面闪络电压大幅降低,从而引发一系列电气设备故障。基于上述问题,文中分析了盆式绝缘子表面电荷的来源与传导途径,采用有限元仿真计算方法构建了二维轴对称仿真模型以及设定相关参数,研究了电压极性、不同电压幅值以及电压极性反转对盆式绝缘子表面电荷分布的影响。结果表明,在直流电压下,凹面主要积聚与外施直流电压极性相反的电荷,凸面主要积聚与直流电压极性相同的电荷,且凹面积聚的电荷密度更大;在极性反转后-100 kV直流电压下,盆式绝缘子表面原先积聚的电荷密度呈现先增大后逐渐减小的趋势,随后转换极性并达到饱和,电场在靠近高压端以及盆式绝缘子沿面0~20 mm处的畸变程度较为明显。电场在盆式绝缘子表面电荷极性发生变化前出现峰值,相比较电荷达到饱和状态,此时盆式绝缘子凹面最大场强增加46%,凸面最大场强增加5.4%。该研究可为直流电压下盆式绝缘子表面电荷分布特性提供指导。

用于心电监测的双层间隔织物干电极制备与表征

为了解决心电动态采集时信号差的问题,以涤纶间隔织物为基底,采用两步法、氯化工艺制备织物干电极,并对其表面形貌、电化学性能和生物电信号采集性能进行了表征。结果表明,经氯化处理10 s的电极具有最优的电化学性能,其阻抗在0.1 Hz时为4 647Ω,静态开路电位振幅为0.114 mV,电压幅度为1.413 mV。相较于湿电极,间隔织物干电极心电信号动态采集性能更好,在不同摆臂角度时采集的心电信号基线漂移小于湿电极,该电极更适合于动态心电信号采集。