Optical optimization of double-side-textured monolithic perovskite–silicon tandem solar cells for improved light management

Tandem configuration-containing perovskite and silicon solar cells are promising candidates for realizing a high power conversion efficiency of 30% at reasonable costs. Silicon solar cells with planar front surfaces used in tandem devices cause high optical losses, which significantly affects their efficiency. Moreover, some studies have explored the fabrication of perovskites on textured silicon cells. However, due to improper texturing, light trapping is not ideal in these devices, which reduces the efficiency. In this work, we optimized the pyramid height of textured silicon cells and efficiently characterized them to achieve enhanced light trapping. Two different kinds of perovskites, namely, Cs_0.17FA_0.6Pb(Br_0.17I_0.7)₃ and Cs_0.25FA_0.6Pb(Br_0.20I_0.7)₃ with wide bandgaps were conformally deposited on textured silicon cells, and the performance of these flat and fully textured tandem devices was numerically analyzed. The thickness of each layer in the tandem cell was optimized in a way to ensure a perfect current match between the top perovskite and bottom silicon subcells. The results indicated that the textured tandem configuration enhances light absorption over a broad spectral range due to the optimized pyramid height compared to flat surfaces. Eventually, the photovoltaic parameters of the proposed tandem cell were compared with the already existing structures, and our design supports large values of open circuit voltage (V_oc) = 1.78 V, short circuit current density (J_sc) = 20.09 mA cm⁻², fill factor (FF) = 79.01%, and efficiency (η) = 28.20% compared to other kinds of tandem solar cells.

Tandem configuration-containing perovskite and silicon solar cells are promising candidates for realizing a high power conversion efficiency of 30% at reasonable costs.     

Electrowetting-on-dielectric (EWOD): Current perspectives and applications in ensuring food safety

Digital microfluidic (DMF) platforms have contributed immensely to the development of multifunctional lab-on-chip systems for performing complete sets of biological and analytical assays. Electrowetting-on-dielectric (EWOD) technology, due to its outstanding flexibility and integrability, has emerged as a promising candidate for such lab-on-chip applications. Triggered by an electrical stimulus, EWOD devices allow precise manipulation of single droplets along the designed electrode arrays without employing external pumps and valves, thereby enhancing the miniaturization and portability of the system towards transcending important laboratory assays in resource-limited settings. In recent years, the simple fabrication process and reprogrammable architecture of EWOD chips have led to their widespread applications in food safety analysis. Various EWOD devices have been developed for the quantitative monitoring of analytes such as food-borne pathogens, heavy metal ions, vitamins, and antioxidants, which are significant in food samples. In this paper, we reviewed the advances and developments in the design of EWOD systems for performing versatile functions starting from sample preparation to sample detection, enabling rapid and high-throughput food analysis.     

Changing the paradigm of organ utilization from PHS increased‐risk donors: an opportunity whose time has come?

Approximately 8–11% of all organ donors are classified by Public Health Service (PHS) as increased‐risk. The proportion of PHS increased‐risk donors is on the rise. At the University of Washington Medical Center, in 2014, the proportion of transplants from PHS increased‐risk donors was 28% of liver transplants and 23% of kidney transplants. Nationally, transplant providers have been reluctant to use organs from PHS increased‐risk donors because of concern for transmission of HIV, HCV, or HBV. There is also patient apprehension when these organs are being offered, and thus the discard rate of these otherwise good quality organs is high. Because of the organ shortage, preventing underutilization of such organs is essential. We provide data and considerations that should be used to guide the use of organs from PHS increased‐risk donors.     

Isolation and Antibiogram of Clostridium tetani from Clinically Diagnosed Tetanus Patients

Clostridium tetani, the etiologic agent of tetanus, produces a toxin that causes spastic paralysis in humans and other vertebrates. This study was aimed for isolation, identification, and determination of antimicrobial susceptibility of C. tetani from clinically diagnosed tetanus patients. Isolation was done from deep-punctured tissues of the foot and arm injuries of 80 clinically diagnosed tetanus patients from the Pakistan Institute of Medical Sciences hospital. We successfully screened out five C. tetani isolates out of 80 samples based on the strain-specific characteristics confirmed through biochemical testing and toxin production. A disc diffusion method was used for antimicrobial susceptibilities and C. tetani isolates showed susceptibility to cefoperazone, chloramphenicol, metronidazole, penicillin G, and tetracycline, but were found to be resistant to erythromycin and ofloxacin. During animal testing, all the infected mice developed symptoms of tetanus. The results showed that identification of C. tetani is possible using biochemical and molecular tools and that the strains of C. tetani isolated had not developed resistance against the antibiotics most often used for the treatment of tetanus.     

Prevalence of dental caries in primary and permanent teeth and its relation with tooth brushing habits among schoolchildren in Eastern Saudi Arabia

Objectives:

To determine the prevalence of dental caries in the primary and permanent teeth, and evaluate the brushing habits of school children in Dammam, Kingdom of Saudi Arabia (KSA).

Methods:

This study was conducted at Dammam, KSA. Oral examination of the participants was conducted from February to May 2014. The total sample size for this cross-sectional study was 711. There were 397 children between the age of 6-9 years, who were examined for primary teeth caries, and 314 between the age 10-12 years were examined for permanent teeth caries. Primary and permanent dentitions were studied for decayed, missing, and filled teeth (dmft [primary teeth], DMFT [permanent teeth]).

Results:

The overall prevalence of dental caries in primary and permanent teeth was almost 73% (n=711). Among the 6-9-year-old, the prevalence of caries was approximately 78% (n=397) whereas, among the 10-12-year-old children, it was approximately 68% (n=314). Mean dmft value among the 6-9-year-olds was 3.66±3.13 with decayed (d) component of 3.28±2.92, missing (m) component of 0.11±0.69, and filled (f) component of 0.26±0.9. Mean DMFT value among the 10-12-year-old children was 1.94±2.0 with decayed (D) component of 1.76±1.85, missing (M) component of 0.03±0.22, and filled (F) of component 0.15±0.73. Daily tooth brushing had a positive effect on caries prevention, and this effect was statistically significant for caries in primary teeth.

Conclusion:

Although the prevalence of dental caries in primary and permanent teeth was not found to be as high as other researchers reported from different cities of KSA, still the prevalence was high considering the World Health Organization future oral health goals. Awareness should be provided to students, as well as, teachers and parents regarding the importance of good brushing habits and regular dental visits.Dental caries is one of the most common cause of extraction of primary teeth in Saudi Arabia.1 In the past few decades, an increase in the prevalence of dental caries has been observed, which can be attributed to a change in lifestyle of Saudis, involving increased consumption of sugary food, carbonated drinks, and lack of awareness towards proper oral health maintenance.2,3 Generally, the prevalence of dental caries in developed countries is decreasing, while in underdeveloped and developing countries, the prevalence is on the rise.4 According to the statistics available from the World Health Organization (WHO), caries prevalence among the 12-year-old children from many European Union states (EU) has decreased considerably from 1970’s to 2006.5 This decline in the caries’ prevalence among EU countries over a period of 35 years could be attributed to an increased awareness of oral hygiene maintenance, and use of fluoridated toothpaste.6 However, among underdeveloped countries where fluoridated toothpaste is not easily available, or not affordable in some cases, caries prevalence is still high.7 The area of dental caries prevalence is of great interest to local and international researchers, which can be indicated by a number of studies that have been performed in developed and developing countries regarding caries’ prevalence.8-10 A study conducted in the urban and rural areas of Lahore, Pakistan to determine whether urbanization and family earnings are related to dental caries reported caries prevalence of 40.5%, and decayed (d), missing (m), and filled (f) teeth (dmft [primary teeth]) score of 1.85 ± 3.26 in preschool children aged 3-5 years,11 while another cross-sectional study performed in Chikar, Pakistan with convenience sampling of 311 schoolchildren revealed an overall DMFT (permanent teeth) score of 3.3 in 5-20-year-olds.12 Several studies have been conducted in different parts of the Kingdom of Saudi Arabia (KSA) to report the prevalence of dental caries in schoolchildren. A study performed in Riyadh reported a dmft score of 6.1, decayed factor of 4.6, and no significant difference in the prevalence of caries in relation to gender among 789 pre-school children.13 Farsi14 conducted a study to develop an association between enamel defects and caries occurrence in Jeddah, KSA, and reported a dmft score of 3.9, and a strong association between enamel defects and caries prevalence among 4-5-year-olds.14 In 2012, caries prevalence in the maxillary and mandibular first molar in the age group of 7-10 years schoolchildren was determined in Abha city, and a mean DMFT of 2.74 was reported.15 It was also concluded in the same study that caries prevalence in the first permanent molars from this region is higher than the recommended standards of the WHO.15 Extensive literature search was carried out to find studies regarding caries’ prevalence from Dammam, KSA. The search resulted in only one study, which was conducted in 2008 on children with cleft lip and palate aged 1-6 years, and it reported a high dmft of 10.54 from Dammam region.16 Since Dammam is one of the largest cities of the Eastern province of KSA, it would be interesting to observe caries’ prevalence among schoolchildren from this city. Therefore, the aim of the present study was to determine the prevalence of dental caries in schoolchildren aged 6-12 years in Dammam, KSA using the dmft/DMFT index of dental caries.     

Segmental <Emphasis Type="Italic">vs.</Emphasis> Extended Colectomy: Measurable Differences in Morbidity,Function, and Quality of Life

Purpose  The colon coordinates fecal elimination while reabsorbing excess fluid. Extended colonic resection removes synchronous and prevents metachronous disease but may adversely alter bowel function and health-related quality of life to a greater degree than segmental resection. This study examined the short-term morbidity and long-term function and quality of life after colon resections of different extents. Methods  Patients undergoing extended resections (n = 201, subtotal colectomy with ileosigmoid or total abdominal colectomy with ileorectal anastomosis) and segmental colonic resections (n = 321) during 1991 to 2003 were reviewed for perioperative outcomes and surveyed for bowel function and quality of life using an institutional questionnaire and a validated quality of life instrument (response rate: 70 percent). Results  The most common indication for extended resections was multiple polyps, and for segmental resections, single malignancy. The complication-free rate was 75.4 percent after segmental resections, 42.8 percent after ileosigmoid anastomosis, and 60 percent after ileorectal anastomosis. Median daily stool frequency was two after segmental resections, four after ileosigmoid anastomosis, and five after ileorectal anastomosis, despite considerable dietary restrictions (55.6 percent) and medication use (19.6 percent daily) after ileorectal anastomosis. Significant proportions of patients felt restricted from preoperative social activity (31.5 percent), housework (20.4 percent), recreation (31.5 percent), and travel (42.6 percent) after ileorectal anastomosis. The overall quality of life after segmental resection, ileosigmoid anastomosis, and ileorectal anastomosis was 98.5, 94.9, and 91.2, respectively. Conclusions  Measurable compromises in long-term bowel function and quality of life were observed after extended vs. segmental resections. The relative differences in patient-related outcomes should be deliberated against the clinical benefits of extended resection for the individual patient. Presented at the Tripartite Colorectal Meeting, Dublin, Ireland, July 5 to 7, 2005.     

Impact of Pelvic Radiotherapy on Morbidity and Durability of Sphincter Preservation After Coloanal Anastomosis for Rectal Cancers

Purpose This study was designed to assess the impact of pelvic radiotherapy on the incidence of complications and colostomy-free survival of patients after a coloanal anastomosis for rectal cancer. Methods A total of 192 patients underwent a coloanal anastomosis between 1982 and 2001: 87 patients did not receive pelvic radiotherapy; 105 patients received pelvic radiotherapy (39 preoperative and 66 postoperative). Early and late complications requiring surgical intervention and the colostomy-free survival rate were assessed by retrospective review of patient records. Results After a median follow-up of 62 months, 151 patients were alive. The most frequent complication was development of an anastomotic stricture (5-year rate of a stricture, 16 percent; 95 percent confidence interval, 10–21). Patients receiving pelvic radiotherapy had a higher rate of complications other than anastomotic strictures, including fecal incontinence, fistulas, abscesses, and bowel obstructions compared with patients not receiving pelvic radiotherapy (5-year rate: 20 percent (95 percent confidence interval, 10–29) vs. 5 percent (95 percent confidence interval, 0–10); P = 0.001). Patients receiving pelvic radiotherapy had a lower colostomy-free survival than did patients not receiving pelvic radiotherapy (5-year colostomy-free rate: 72 percent (95 percent confidence interval, 62–84) vs. 92 percent (95 percent confidence interval, 86–98); P < 0.001). There was no significant difference in the colostomy-free survival of patients receiving preoperative and postoperative pelvic radiotherapy. Conclusions After coloanal anastomosis, a significant number of patients will have complications requiring surgical intervention, and some will require a permanent colostomy. Pelvic radiotherapy, whether it is administered preoperatively or postoperatively, significantly increases the need for a permanent colostomy.