Structure-Property Relationships for the Electronic Applications of Bis-Adduct Isomers of Phenyl-C61 Butyric Acid Methyl Ester

Higher adducts of a fullerene, such as the bis-adduct of PCBM (bis-PCBM), can be used to achieve shallower molecular orbital energy levels than, for example, PCBM or C60. Substituting the bis-adduct for the parent fullerene is useful to increase the open-circuit voltage of organic solar cells or achieve better energy alignment as electron transport layers in, for example, perovskite solar cells. However, bis-PCBM is usually synthesized as a mixture of structural isomers, which can lead to both energetic and morphological disorder, negatively affecting device performance. Here, we present a comprehensive study on the molecular properties of 19 pure bis-isomers of PCBM using a variety of characterization methods, including ultraviolet photoelectron spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, single crystal structure, and (time-dependent) density functional theory calculation. We find that the lowest unoccupied molecular orbital of such bis-isomers can be tuned to be up to 170 meV shallower than PCBM and up to 100 meV shallower than the mixture of unseparated isomers. The isolated bis-isomers also show an electron mobility in organic field-effect transistors of up to 4.5 × 10-2 cm2/(V s), which is an order of magnitude higher than that of the mixture of bis-isomers. These properties enable the fabrication of the highest performing bis-PCBM organic solar cell to date, with the best device showing a power conversion efficiency of 7.2%. Interestingly, we find that the crystallinity of bis-isomers correlates negatively with electron mobility and organic solar cell device performance, which we relate to their molecular symmetry, with a lower symmetry leading to more amorphous bis-isomers, less energetic disorder, and higher dimensional electron transport. This work demonstrates the potential of side chain engineering for optimizing the performance of fullerene-based organic electronic devices.

Controlling swelling in mixed transport polymers through alkyl side-chain physical cross-linking

Semiconducting conjugated polymers bearing glycol side chains can simultaneously transport both electronic and ionic charges with high charge mobilities, making them ideal electrode materials for a range of bioelectronic devices. However, heavily glycolated conjugated polymer films have been observed to swell irreversibly when subjected to an electrochemical bias in an aqueous electrolyte. The excessive swelling can lead to the degradation of their microstructure, and subsequently reduced device performance. An effective strategy to control polymer film swelling is to copolymerize glycolated repeat units with a fraction of monomers bearing alkyl side chains, although the microscopic mechanism that constrains swelling is unknown. Here we investigate, experimentally and computationally, a series of archetypal mixed transporting copolymers with varying ratios of glycolated and alkylated repeat units. Experimentally we observe that exchanging 10% of the glycol side chains for alkyl leads to significantly reduced film swelling and an increase in electrochemical stability. Through molecular dynamics simulation of the amorphous phase of the materials, we observe the formation of polymer networks mediated by alkyl side-chain interactions. When in the presence of water, the network becomes increasingly connected, counteracting the volumetric expansion of the polymer film.

Analysis of Lung Cancer Cases Presenting in Outpatient Department of University Hospital of Nepal

Background Lung cancer is one of the leading cause of cancer related death. Most common histopathology of lung cancer is non-small cell carcinoma of which adenocarcinoma is the most common. There are limited number of studies done in Nepal to know different aspects of lung cancer. Objective To know demographic parameters of patients diagnosed as lung cancer in a university hospital. The study also aims to know the different histopathological diagnosis of lung cancer. Method All the patients presenting to outpatient department (Cardio Thoracic and Vascular unit) of Dhulikhel Hospital, if are diagnosed as cancer of lung/bronchus will be included in the study. The duration of the study was January 2017 to December 2021. The details on age, gender, presenting symptoms, histopathology of lung cancer, operability will be included in database and will be analyzed. Result There were total of 127 patients diagnosed as lung cancer. Male:female ratio was 1.7:1. Overall mean age was 63.23 years (SD 13.5 years, Range 19-89 years). Non small cell carcinoma was the most common type of lung cancer with 83.7%. In non small cell carcinoma, most common type was Squamous cell carcinoma followed by undifferentiated and Adenocarcinoma. Only five (3.93%) cases were in operable stage. Conclusion Despite the fact that lung cancer is one of the most common cancer, patients usually present late and moslty are not in operable stage. This study shows that squamous cell carcinoma is the most common histopathology in lung cancer cases.

Impact of Side-Chain Hydrophilicity on Packing, Swelling, and Ion Interactions in Oxy-Bithiophene Semiconductors

Exchanging hydrophobic alkyl-based side chains to hydrophilic glycol-based side chains is a widely adopted method for improving mixed-transport device performance, despite the impact on solid-state packing and polymer-electrolyte interactions being poorly understood. Presented here is a molecular dynamics (MD) force field for modeling alkoxylated and glycolated polythiophenes. The force field is validated against known packing motifs for their monomer crystals. MD simulations, coupled with X-ray diffraction (XRD), show that alkoxylated polythiophenes will pack with a "tilted stack" and straight interdigitating side chains, whilst their glycolated counterpart will pack with a "deflected stack" and an s-bend side-chain configuration. MD simulations reveal water penetration pathways into the alkoxylated and glycolated crystals-through the π-stack and through the lamellar stack respectively. Finally, the two distinct ways triethylene glycol polymers can bind to cations are revealed, showing the formation of a metastable single bound state, or an energetically deep double bound state, both with a strong side-chain length dependence. The minimum energy pathways for the formation of the chelates are identified, showing the physical process through which cations can bind to one or two side chains of a glycolated polythiophene, with consequences for ion transport in bithiophene semiconductors.

A case of thymoma in myasthenia gravis: Successful outcome after thymectomy

INTRODUCTION

Thymic abnormalities occur as hyperplasia and thymoma. Myasthenia gravis is commonly present in thymoma. Thymectomy possesses risk due to anatomical proximity with vital thoracic structures and myasthenia crisis.

PRESENTATION OF CASE

Forty five years female with complaints of difficulty swallowing and weakness of upper limb muscles upon investigation showed mass in mediastinum and antibody test for myasthenia gravis positive. Medical management was done for a month followed by thymectomy. There were no intra and postoperative complications. Medical management was stopped one month after surgery and she is symptom free.

DISCUSSION

Thymectomy is the standard of care where median sternotomy is the mainstay approach to surgery. Various other surgical approaches and complications revolving around surgery has been discussed.

CONCLUSION

Surgical removal of thymoma cured myasthenia gravis in our case. We focused on proper preoperative optimization of myasthenia gravis symptoms before thymectomy.

Factors Affecting Recanalisation after Optimal Management of Deep Vein Thrombosis; A single institution based study

Background Presence of recanalisation will favour for better physiological recovery after medical management of Deep Vein Thrombosis (DVT) along with lesser chances of post thrombotic syndrome. Rate of recanalisation is varied and can range from 43-57% and the factors that affect recanalisation are still a dilemma. Objective To know the factors for recanalisation following Deep Vein Thrombosis. Method This is a single institution based retrospective-prospective analytical study encompassing all ultrasonologically diagnosed cases of Deep Vein Thrombosis in adults from January 2015 to November 2017. All the cases were admitted with oral warfarin bridged by Heparin/ Enoxaparin and were discharged once International Normalization Ratio was in therapeutic range. The patients were followed up for three months with minimal of three outpatient followup. Best finding in the doppler ultrasonography (done by Acuson P500, Seimens) in relation to recanalisation was taken for the study. Result There were 67 cases of Deep Vein Thrombosis. Of these cases male to female ratio was 0.91. The mean age was 48.07. Most common extent was up to common femoral vein (47.8%) followed by upto popliteal vein (40.3%). Remaining 11.9% had extension upto iliac veins. There was no recanalisation in 2 cases (3%). Partial recanalisation was seen in 23 cases (34.3%) while complete recanalisation was seen in 42 cases (62.7%). Recanalisation is more in DVT involving popliteal vein while it decreases as the extension goes up. In contrast to 79.4% complete recanalisation in popliteal vein, that in common femoral vein is 62.5% while in iliac vein is only 37.5%. Mean age in no recanalisation group is much younger than partial or complete recanalisation groups. Conclusion Recanalisation following Deep Vein Thrombosis distal to popliteal vein is more than that in proximal Deep Vein Thrombosis. The information on recanalization can be considered to use to decide upon the duration of medical management of Deep Vein Thrombosis.

Abnormal Venous Dilatation other than Typical Varicose Vein, Rare Encounters

Varicose vein, one of the common vascular illnesses is usually a disease in lower limb. This is due to reflux of blood from deep venous system to superficial venous system. Rarely, this disease can also happen in veins in different location. Four such rare encounters are mentioned in this case series.

Optimal Starting Dose of Warfarin for Treatment of Deep Vein Thrombosis in Nepalese Context, A Retrospective- Prospective Institutional Review

Background Deep vein thrombosis (DVT) requires an early establishment of effective anticoagulation in order to reduce harms and cost of concomitant treatments. Selection of the right warfarin dose at the start of treatment is important. Objective To know ideal starting dose of warfarin in adult with Deep Vein Thrombosis of our population. Method This is a retrospective-prospective single institution based analytical study including Deep Vein Thrombosis in adults from January 2015 to November 2017. On the first half (January 1, 2015 to July 31, 2016) of the study period, the cases were given 3mg of warfarin as initial dose (Group 1); while in the second half (August 1, 2016 to November 31, 2017) cases were given 5mg as the initial dose (Group 2). Two sequential International Normalisation Ratio (INR) within therapeutic range is considered as target attained. Result There were total of 63 patients (M:F=1:1.03) of which 85.7% (n=54) cases were acute deep vein thrombosis and 14.3% were chronic cases. Mean final dose of warfarin was 6.03 mg; where it was 6.50 mg in group 1 and 5.63 mg in group 2, p=0.11. Difference between final dose and starting dose it was found to be 3.5 mg in Group 1 while that was only 0.63 mg in Group 2 (p<0.01). Conclusion Lesser change in dose of warfarin from its initial starting dose (5 mg) was noticed in group 2. Warfarin 6 mg as ideal starting dose can be recommended but larger, multicentric and follow up studies are essential to substantiate the findings.

Influence of the Hole Transporting Layer on the Thermal Stability of Inverted Organic Photovoltaics Using Accelerated-Heat Lifetime Protocols

High power conversion efficiency (PCE) inverted organic photovoltaics (OPVs) usually use thermally evaporated MoO₃ as a hole transporting layer (HTL). Despite the high PCE values reported, stability investigations are still limited and the exact degradation mechanisms of inverted OPVs using thermally evaporated MoO₃ HTL remain unclear under different environmental stress factors. In this study, we monitor the accelerated lifetime performance under the ISOS-D-2 protocol (heat conditions 65 °C) of nonencapsulated inverted OPVs based on the thiophene-based active layer materials poly(3-hexylthiophene) (P3HT), poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7), and thieno[3,2-b]thiophene-diketopyrrolopyrrole (DPPTTT) blended with [6,6]-phenyl C₇₁-butyric acid methyl ester (PC[70]BM). The presented investigation of degradation mechanisms focus on optimized P3HT:PC[70]BM-based inverted OPVs. Specifically, we present a systematic study on the thermal stability of inverted P3HT:PC[70]BM OPVs using solution-processed poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and evaporated MoO₃ HTL. Using a series of measurements and reverse engineering methods, we report that the P3HT:PC[70]BM/MoO₃ interface is the main origin of failure of the P3HT:PC[70]BM-based inverted OPVs under intense heat conditions, a trend that is also observed for the other two thiophene-based polymers used in this study.

Initial Experience of Complex Peripheral Bypass Surgery at Dhulikhel Hospital, Kathmandu University Hospital

Peripheral arterial disease is seemingly silent yet is a major pubic health problem with limb threatening and life threatening consequences. This condition can initially be asymptomatic and gradually may progress to intermittent claudication and finally to critical ischemia. When conservative management is not sufficient and there is option of surgical management, peripheral bypass surgery is an established modality of treatment of peripheral arterial disease. We present our initial cases of peripheral arterial bypass surgery all of which are technically demanding surgeries. All the cases have resulted into limb salvage until current follow-up.

Simultaneous topographical, electrical and optical microscopy of optoelectronic devices at the nanoscale

Novel optoelectronic devices rely on complex nanomaterial systems where the nanoscale morphology and local chemical composition are critical to performance. However, the lack of analytical techniques that can directly probe these structure-property relationships at the nanoscale presents a major obstacle to device development. In this work, we present a novel method for non-destructive, simultaneous mapping of the morphology, chemical composition and photoelectrical properties with <20 nm spatial resolution by combining plasmonic optical signal enhancement with electrical-mode scanning probe microscopy. We demonstrate that this combined approach offers subsurface sensitivity that can be exploited to provide molecular information with a nanoscale resolution in all three spatial dimensions. By applying the technique to an organic solar cell device, we show that the inferred surface and subsurface composition distribution correlates strongly with the local photocurrent generation and explains macroscopic device performance. For instance, the direct measurement of fullerene phase purity can distinguish between high purity aggregates that lead to poor performance and lower purity aggregates (fullerene intercalated with polymer) that result in strong photocurrent generation and collection. We show that the reliable determination of the structure-property relationship at the nanoscale can remove ambiguity from macroscopic device data and support the identification of the best routes for device optimisation. The multi-parameter measurement approach demonstrated herein is expected to play a significant role in guiding the rational design of nanomaterial-based optoelectronic devices, by opening a new realm of possibilities for advanced investigation via the combination of nanoscale optical spectroscopy with a whole range of scanning probe microscopy modes.

Ultrafast decoherence dynamics govern photocarrier generation efficiencies in polymer solar cells

All-organic-based photovoltaic solar cells have attracted considerable attention because of their low-cost processing and short energy payback time. In such systems the primary dissociation of an optical excitation into a pair of photocarriers has been recently shown to be extremely rapid and efficient, but the physical reason for this remains unclear. Here, two-dimensional photocurrent excitation spectroscopy, a novel non-linear optical spectroscopy, is used to probe the ultrafast coherent decay of photoexcitations into charge-producing states in a polymer:fullerene based solar cell. The two-dimensional photocurrent spectra are interpreted by introducing a theoretical model for the description of the coupling of the electronic states of the system to an external environment and to the applied laser fields. The experimental data show no cross-peaks in the twodimensional photocurrent spectra, as predicted by the model for coherence times between the exciton and the photocurrent producing states of 20 fs or less.

Influence of polymer-blend morphology on charge transport and photocurrent generation in donor-acceptor polymer blends

Monte Carlo algorithms are used to simulate the morphologies adopted by polymer chains in a polymer-blend film in the limits where the chains are mutually attractive (homophilic regime) and mutually repulsive (heterophilic regime) and then to simulate the drift transport of charges through the polymer chains. In the homophilic regime, chains aggregate into tangled domains resulting in a relatively high percolation threshold, a high density of configurational trap states, and slow, dispersive charge transport. In the heterophilic regime at the same polymer volume fraction, chains self-organize into a lacework pattern resulting in a low percolation threshold and efficient, trap-free charge transport. For homophilic morphologies interchain hopping is rate-limiting and mobility is insensitive to chain length, whereas for heterophilic morphologies intrachain transport is important and mobility increases with increasing chain length. The morphologies are used in simulations of photocurrent quantum efficiency for donor-acceptor blend photodiodes, which show that the effects of morphology on charge pair generation and recombination compete with the effect on transport, such that the optimum blend composition is sensitive to both morphology and recombination rate. We conclude that it is essential to consider the connectivity of and morphology adopted by polymer chains in the optimization of materials for organic solar cells.

Surgical reconstruction of the mitral valve

From Cutler's first attempt to treat the mitral valve by inserting a tenotomy knife through the left ventricle, to Carpentier's introduction of several repair techniques and a functional classification for assessing mitral valve lesions, the history of mitral valve treatment is exciting. Mitral diseases may be degenerative, ischaemic, infective or rheumatic, with or without superimposed impaired left ventricular function and calcification. Understanding the underlying pathological features is also important in determining whether mitral valve repair is feasible, how the valve should be repaired and the prospect for long-term durability of the repair. Recent advances in minimally invasive mitral valve surgery are promising but more effort is needed to ensure timely mitral valve repair.

The role of pharmacists in HIV/STD prevention: evaluation of an STD syndromic management intervention in Nepal

OBJECTIVE

To evaluate the effects of a pilot sexually transmitted disease (STD) syndromic case management training for pharmacists in Nepal on STD drug dispensing behavior, HIV/STD prevention communication, and condom promotion and sales.

METHODS

Pre- and post-intervention interviews with samples of 160 pharmacists were conducted utilizing the simulated client method to collect data on pharmacists' response to men reporting urethral discharge. In order to assess the long-term effects, a sub-sample of 38 pharmacists trained 7-9 months before the follow-up survey was analysed separately.

RESULTS

There were no significant differences in the percentages of pharmacists who suggested taking medications, dispensed medications, or referred clients to a physician. The proportion of pharmacists who recommended an injection declined from 27% to 14%. Prior to the intervention, only one pharmacist (0.8%) dispensed the correct drugs and regimen for the syndromic treatment of urethritis. This increased to 45% immediately following the training. In a sub-sample of pharmacists who were interviewed 7-9 months after the training, the correct drugs and regimen were dispensed by 26%. The proportion of pharmacists who recommended to clients to have their sex partners treated increased from 5% to 21%. Although the proportion of pharmacists who suggested condom use increased from 14% to 24%, the proportion of pharmacists actually selling a condom or giving advice on HIV testing remained low and unchanged pre- and post-intervention. Over one-third of pharmacists mentioned HIV or AIDS in their interactions with clients, compared to 9% prior to the intervention.

CONCLUSIONS

The findings suggest that STD services provided by pharmacists can be significantly improved through a short-term training intervention, although the improvements are modest and probably time-limited. Interventions must be more intensive and combined with regular follow-ups if they are to meet their desired goals of improving STD treatment in a pharmacy setting.

Delayed presentation of diaphragmatic hernia in a young and fit patient requiring emergency management

Diaphragmatic hernia, when they do present in adults, can manifest as a life threatening complication. Symptoms might initially be minimal in young and fit patients. They can also easily mimic complications like peptic ulcer perforation or tension pneumothorax and early pathophysiological correlation is required to reach an early diagnosis and treatment. DOI: 10.3126/jcmsn.v6i3.4077Journal of College of Medical Sciences-Nepal, 2010, Vol. 6, No. 3 pp.50-51