Pylorus-preserving gastrectomy for early gastric cancer.

Pylorus-preserving gastrectomy (PPG) has been widely accepted as a function-preserving gastrectomy for middle-third early gastric cancer (EGC) with a distal tumor border at least 4 cm proximal to the pylorus. The procedure essentially preserves the function of the pyloric sphincter, which requires to preserve the upper third of the stomach and a pyloric cuff at least 2.5 cm. The suprapyloric and infrapyloric vessels are usually preserved, as are the hepatic and pyloric branches of the vagus nerve. Compared with distal gastrectomy, PPG has significant advantages in preventing dumping syndrome, body weight loss and bile reflux gastritis. The postoperative complications after PPG have reached an acceptable level. PPG can be considered a safe, effective, and superior choice in EGC, and is expected to be extensively performed in the future.

Association of Breastfeeding and Neonatal Jaundice With Infant Neurodevelopment.

INTRODUCTION: Exclusive breastfeeding is advantageous for infant neurodevelopment. Nevertheless, insufficient human milk supply in exclusively breastfed infants may elevate the risk of neonatal jaundice, which can potentially result in neurological harm. Whether mothers should adhere to exclusive breastfeeding in infants with neonatal jaundice remains unclear. METHODS: Data comes from the Jiangsu Birth Cohort (JBC), a prospective and longitudinal birth cohort study in China. A total of 2,577 infants born from November 2017 to March 2021 were included in the analysis. Multivariate linear regression models were used to analyze the associations between breastfeeding status, neonatal jaundice, and their interaction with infant neurodevelopment. Analysis was performed in 2022. RESULTS: Compared with "exclusive breastfeeding," fine motor scores of infants were lower for "mixed feeding" (ßadj, -0.16; 95% CI, -0.29 to -0.03; p=0.016) and "no breastfeeding" (ßadj, -0.41; 95% CI, -0.79 to -0.03; p=0.034). Compared with "no neonatal jaundice," infants with "severe neonatal jaundice" had lower scores for cognition (ßadj, -0.44; 95% CI, -0.66 to -0.23; p<0.001) and fine motor (ßadj, -0.19; 95% CI, -0.35 to -0.03; p=0.024). In infants with severe neonatal jaundice, the termination of exclusive breastfeeding before 6 months was associated with worse cognition (ßadj, -0.28; 95% CI, -0.57 to 0.01), while this association was not observed in those without neonatal jaundice (ßadj, 0.09; 95% CI, -0.26 to 0.43). CONCLUSIONS: Exclusive breastfeeding for the first 6 months is beneficial to the neurodevelopment of infants, especially in those with severe neonatal jaundice.

Association between PM2.5 exposure and the outcomes of ART treatment: A prospective birth cohort study.

Exposure to fine particulate matter (PM2.5) has been reported to be adversely associated with reproductive health. However, current evidence on PM2.5 exposure adversely influencing pregnancy outcomes remains inconclusive. Women receiving assisted reproductive technology (ART) treatment are under close monitoring with regards to their treatment process, which make them great study population to assess the impact of PM2.5 in the post-implantation period. Therefore, within a prospective cohort study in Jiangsu, China, we assessed the associations between exposure to ambient PM2.5 and the outcomes of ART treatment, including implantation failure, biochemical pregnancy loss, clinical pregnancy and live birth, in 2431 women who underwent the first fresh embryo transfer or frozen embryo transfer cycle. High-performance machine-learning model was performed to estimate daily PM2.5 exposure concentrations at 1 km spatial revolution. Exposure windows were divided into seven periods according to the process of follicular and embryonic development in ART. Generalized estimation equations (GEE) was used to assess the association between PM2.5 and ART outcomes. Higher PM2.5 exposure was associated with decreased probability of clinical pregnancy (RR: 0.98, 95 % CI: 0.96-1.00). Each 10 µg/m3 increase in PM2.5 exposure in the duration from hCG test to 30 days after embryo transfer (Period 7) was positively associated with the risk of biochemical pregnancy loss (RR: 1.06, 95 % CI: 1.00-1.13), and more prominent effects were observed in women undergoing fresh embryo transfer. Null associations were observed between PM2.5 exposure and implantation failure or live birth at any exposure window. Collectively, our study suggested that exposure to PM2.5 increased the risk of adverse treatment outcomes in the ART population. Thus, for women opting for ART treatment, particularly those who select fresh embryo transfer cycles, additional evaluation of PM2.5 exposure before treatment might be of value in decreasing the risk of adverse pregnancy outcomes.

Identification of lncRNA and mRNA regulatory networks associated with gastric cancer progression.

Gastric cancer is a tumor type characterized by lymph node metastasis and the invasion of local tissues. There is thus a critical need to clarify the molecular mechanisms governing gastric cancer onset and progression to guide the treatment of this disease. Long non-coding RNAs and mRNA expression profiles associated with early and local advanced gastric cancer were examined through microarray analyses, with GO and KEGG analyses being employed as a means of exploring the functional roles of those long non-coding RNAs and mRNAs that were differentially expressed in gastric cancer. In total, 1005 and 1831 lncRNAs and mRNAs, respectively, were found to be differentially expressed between early and local advanced gastric cancer. GO and KEGG analyses revealed several pathways and processes that were dysregulated, including the RNA transport, ECM-receptor interaction, and mRNA splicing pathways. In co-expression networks, E2F1, E2F4, and STAT2 were identified as key transcriptional regulators of these processes. Moreover, thrombospondin-2 was confirmed as being expressed at high levels in more advanced gastric cancer by both the GEO and TCGA databases. RNA-sequencing analyses of SGC-790 cells transfected to express thrombospondin-2 further revealed this gene to enhance NF-kB and TNF pathway signaling activity. These results offer insight into gastric cancer-related regulatory networks and suggest thrombospondin-2 to be an important oncogene that drives the progression of this deadly cancer type.

Mechanical intestinal obstruction in underweight, elderly women due to an incarcerated obturator hernia.

BACKGROUND: Obturator hernia is an infrequent pelvic hernia observed in elderly, emaciated and multiparous women. It often presents with nonspecific clinical symptoms, making it difficult to diagnose. METHODS: We conducted a retrospective descriptive study on 11 patients admitted to our hospital for obturator hernia from 2009 to 2020. RESULTS: All the patients were diagnosed with intestinal obstruction due to incarcerated obturator hernia preoperatively. Eight patients underwent laparotomy with low midline incision. Laparoscopic approach was tried on the other three patients with two patients converting to open surgery because of inadequate visualization, and only one patient received laparoscopic repair. Of the 10 patients receiving laparotomy, seven cases received obturator hernia repair with a match and three cases were subjected to bowel resection (two cases intestinal necrosis and one case intestinal perforation). Simple peritoneal closure was performed on the three contaminated cases. One patient died of septic shock and multiple organ failure. CONCLUSION: The emergent computed tomography allow for early and precise diagnosis of incarcerated obturator hernia. Laparotomy with low midline incision is commonly used to manage obturator hernia in an emergency, whereas laproscopic approach may only apply to some selected cases.

Current status of internal hernia after gastrectomy for gastric cancer.

BACKGROUND: Internal hernia is a well-known postoperative complication after Roux-en-Y gastric bypass. However, it has not been considered a recognized complication for gastric cancer. METHODS: We reviewed the literature in the past decade to clarify the current status of internal hernia after gastrectomy including its incidence, high-risk factors, and treatment. RESULTS: The incidence of internal hernia after gastrectomy was found to be between 0.2 and 5.63%, and the median interval time was less than 2 years. High-risk factors include laparoscopic approach, non-closure of all the mesenteric defects, and Roux-en-Y reconstruction. The rate of bowel resection was significantly higher than that of adhesive small bowel obstruction. CONCLUSION: The true incidence of internal hernia after gastrectomy is generally underestimated. Closure of all the mesenteric defects is one of the most effective methods to prevent postoperative internal hernia. Early surgical exploration is necessary when internal hernia is suspected.

Identification and analysis of anovel variant of TRAPPC2 in a X-linked spondyloepiphyseal dysplasia tarda pedigree / 中华骨科杂志

Objective:To provide experimental evidence for genetic counseling and prenatal diagnosis by analyzing the clinical characteristics, screening and identification of the function of suspicious variants in a X-1inked spondyloepiphyseal dysplasia tarda (SEDT) family.Methods:The family members' medical history, general physical examination, femur, spine X-ray examination were collected. Peripheral blood samples of the family members were collected and DNA was extracted from these samples. Sequencing clinical whole exons of proband DNA by targeted gene high-throughput sequencing method, then analysis sequencing data. The suspicious mutation was confirmed in pedigree members by PCR and Sanger sequencing. Reverse transcription polymerase chain reaction (RT-PCR) experiments of total RNA from blood lymphocytes were performed. The amplification of exons 3 and 4 of the pathogenic gene were amplified and identified by agarose gel. The expression of the pathogenic gene was also detected.Results:Three affected males of the family were diagnosed with SEDT according to their clinical and radiological features. A nonsense mutation in the transport protein particle complex subunit 2 ( TRAPPC2) gene NM_001011658: c.91A>T (p.K31*) was found in the proband using whole exome sequencing. This variation was also detected in his cousin, but not in non-phenotypic members of the family. The RT-PCR result for amplification of exon 3 and 4 of peripheral blood lymphocytes was the same as those of normal controls, indicating that the mutation did not affect the splicing of transcripts. qPCR results showed that the transcriptional expression of TRAPPC2 in patients was significantly lower than that in family normal controls and normal people controls. Conclusion:Identification of the novel nonsense mutation (c.91A>T) in the SEDT family enables early patients screening, carrier detection, genetic counseling, prenatal diagnosis, and clinical prevention and treatment. The detailed genotype/phenotype descriptions contribute to the SEDT mutation spectrum. The study of the function of TRAPPC2 mutation will help to further elucidate the role of sedlin in cartilage.

Comparative study on Sichuan yak pericardium and Australian cattle pericardium / 生物医学工程学杂志

Currently, as the key raw material of artificial biological heart valve, bovine pericardium is mainly depend on import and has become a "bottleneck" challenge, greatly limiting the development of domestic biological heart valve. Therefore, the localization of bovine pericardium is extremely urgent. In this study, the pericardium of Sichuan yak was compared with that of Australian cattle in terms of fundamental properties and anti-calcification performance. The results demonstrated that the appearance and thickness of yak pericardium were more advantageous than the Australian one. Sichuan yak pericardium and Australian cattle pericardium had comparable performance in shrinkage temperature, mechanical test and anti-calcification test. This study preliminarily verifies the feasibility of substitution of Australian cattle pericardium by Sichuan yak pericardium and promotes the progression of bovine pericardium localization with data support.

Esophagus two-step-cut overlap method in esophagojejunostomy after laparoscopic gastrectomy.

PURPOSE: Esophagojejunostomy is a challenging step in laparoscopic gastrectomy. Although the overlap method is a safe and feasible approach for esophagojejunostomy, it has several technical limitations. We developed novel modifications for the overlap method to overcome these disadvantages. METHODS: Forty-eight consecutive gastric cancer patients underwent totally laparoscopic total gastrectomy or laparoscopic proximal gastrectomy with double-tract reconstruction at our institution from January 2019 to April 2020 using the overlap method with the following modifications. The esophagus was initially rotated by 90° counterclockwise, followed by transection of two-thirds of the esophageal diameter. The unstapled esophagus was then transected with a harmonic ultrasonic scalpel to enable esophagostomy at the posterior side of the esophagus. A side-to-side esophagojejunostomy was then formed at the posterior side of the esophagus using an endoscopic linear stapler through the right lower trocar. The common entry hole was closed via hand sewing method using V-Loc suture. This procedure was termed "esophagus two-step-cut overlap method." RESULTS: Only one patient suffered from esophagojejunal anastomotic leakage but subsequently recovered after conservative treatment. Patients did not experience anastomotic bleeding or stricture. CONCLUSION: Our modified overlap method provides satisfactory surgical outcomes and overcomes several technical limitations, such as entering the false lumen of the esophagus, unnecessary pollution caused by nasogastric tube, and unintended left crus stapling during anastomosis.

Current status of laparoscopic proximal gastrectomy in proximal gastric cancer: Technical details and oncologic outcomes.

The incidence of proximal gastric cancer has been increasing continuously. This status has prevailed despite the application of laparoscopic proximal gastrectomy as a surgical treatment for early proximal gastric cancer. The widespread adoption and standardization of this surgical procedure as the primary treatment for the abovementioned cancer has been hampered by the lack of consensus on the optimal reconstruction method after proximal gastrectomy. In addition, the oncological safety of proximal gastrectomy for advanced gastric disease remains unclear. We reviewed the English-language literature to clarify the current status of laparoscopic proximal gastrectomy in proximal gastric cancer. Japanese gastric cancer guidelines have suggested three types of reconstructions for proximal gastrectomy, namely, esophagogastrostomy, double-tract reconstruction, and jejunal interposition. Optimal reconstruction methods remain to be determined because of the lack of adequately performed and well-designed randomized controlled trials. The technical complexity and challenging implementation of reconstruction procedures have resulted in several complications with anastomoses. Multicenter randomized controlled trials are necessary to evaluate the various reconstruction methods and the oncological safety of laparoscopic proximal gastrectomy for advanced gastric disease.

Challenges surrounding postoperative adjuvant chemotherapy for T2N0 gastric cancer.

Determining the requirement for adjuvant chemotherapy in patients with stage IB gastric cancer (GC), and particularly for those with stage T2N0 (muscularis propria) disease, remains challenging. Patients with stage II/III disease benefit from postoperative adjuvant therapy; however, the randomized trials examining whether such therapy affords any survival benefit to patients with T2N0 disease are not sufficient. Current evidence suggests that not all patients with T2N0 disease should undergo such treatment, but only those with a high risk. To date, a number of retrospective studies have attempted to identify factors that are predictive of increased risk in an effort to guide adjuvant therapy-related clinical decision making. The National Comprehensive Cancer Network and the Chinese Society of Clinical Oncology have published guidelines regarding factors associated with increased patient risk. As a result, treatment decisions for patients with stage T2N0 disease are currently determined on an individualized basis, in light of risk factors and the potential benefits of treatment. The present review surveyed current evidence related to the treatment of patients with high-risk GC and highlighted the potential avenues for future investigated.

Integrated Profiling Revealed Potential Regulatory Networks Among Long Noncoding RNAs and mRNAs in Mucosal Gastric Cancer.

Gastric cancer is one of the most commonly occurring cancers worldwide. Investigation of long noncoding RNAs is of increasing interest, particularly in relation to their contribution to progression and prognosis of gastric cancers; however, insufficient studies been performed investigating the part of long noncoding RNAs play in gastric cancer carcinogenesis. Patterns of dysregulated long noncoding RNA and messenger RNA between mucosa gastric cancer and adjacent normal tissues were identified using long noncoding RNAs microarray analysis. Quantitative real-time polymerase chain reaction was conducted as a means to verify the obtained data. Both Gene Ontology and Kyoto Encyclopedia of Genes and Genomes  (KEGG) pathway analyses were subsequently used to investigate the function of dysregulated long noncoding RNAs and messenger RNAs. Cis and trans action was used to predict the possible targets of long noncoding RNAs, and a coexpression network was created to simulate the complex intergenic interactions. Ninety-five dysregulated long noncoding RNAs and 123 messenger RNAs were identified, and quantitative real-time polymerase chain reaction was used to validate 6 filtered long noncoding RNAs. Gene Ontology and KEGG pathway analyses identified several remarkably biological processes and signaling pathways, including spliceosome, RNA transport, and ubiquitin-mediated proteolysis. The transcriptional factors MYC, GABPA, and E2F1 were found to play a central function in the long noncoding RNAs process, as indicated by the coexpression network. This study revealed the dysregulated long noncoding RNA profiles of mucosal gastric cancer. The results shed light on the biological function of long noncoding RNAs in gastric cancer pathogenesis. This provides useful information for exploring potential early screening biomarkers in gastric cancer.

Vascular anatomical variation in laparoscopic right hemicolectomy.

Laparoscopic complete mesocolic excision is gradually becoming the standard surgical approach in colon cancer therapy, the core element of which is central vascular ligation. However, this increases the difficulty for surgeons, particularly in the context of right colectomy, which encounters complex vascular anatomy. This study aimed to examine vascular variations that occur during laparoscopic right hemicolectomy through a review of the medical literature. We demonstrated that the ICA and MCA are evident in the majority of patients. The RCA was inconsistently present ranging from 12% to 45%. The ICA passed the SMV anteriorly or posteriorly at average rates. However, the RCA passed anterior to the SMV in most patients. Regarding intravenous, the ICV was consistently present, whereas the RCV was absent in up to 80% of patients. The GTH was present in nearly 80% of patients. We classified the vascular variations by the location of the branches instead of using numerical classification. The GCT and GPCT were common types whilst the GPT was relatively rare. In summary, detailed information on the vascular anatomical variations occurring on the right-side of the colon is vital. Failure to identify variations during surgical procedures can result in unwanted bleeding. Thus, we advocate for the use of the ICV as an anatomic marker during surgery.

School bullying and its influencing factors in higher vocational college students in western Hunan province / 中国学校卫生

Objective@#To understand current situation and influencing factors of school bullying among left-behind and non left-behind students in vocational colleges in western Hunan, and to provide reference for the prevention and control of campus bullying in vocational colleges in poverty-stricken areas.@*Methods@#A multi-stage stratified random cluster sampling method was used to select 1 241 students from higher vocational colleges in Xiangxi for questionnaire survey. The survey included basic demographic characteristics, health-related behaviors and school bullying. Associcted factors were compared among students with and without school bullying by using the χ2 test and Logistic regression.@*Results@#The reported rate of school bullying in vocational colleges was 41.82%. The reported rate of left-behind students (45.05%) was higher than that of non-left-behind students (39.21%). The difference was statistically significant (χ2=4.29,P<0.05). Multivariate unconditional Logistic regression showed that male students and good parental relationship negatively associated with school bullying among left-behind students(OR=0.55，0.47). While rural students, 5 years of senior vocational, smoking, drinking, and game addiction were positively associated with school bullying among left-behind students(OR=1.93,2.57,2.51,3.95,4.73); good relationship with mothers was associated with less school bullying(OR=0.40), while smoke, drinking and game addiction was associated with more school bullying among non left-behind students(OR=1.86,2.32，3.81)(P<0.05).@*Conclusion@#School bullying among students in higher vocational colleges in western Hunan is highly prevalent. The reporting rate among left-behind students is higher than that of non-left-behind students. Due to different factors, joint intervention measures by government, schools and families should be carried out as soon as possible.

Small bowel metastasis from pulmonary rhabdomyosarcoma causing intussusception: a case report.

BACKGROUND: Rhabdomyosarcoma (RMS), especially primary pulmonary RMS, is an extremely rare type of soft tissue sarcoma in adults. Small bowel is an uncommon site for metastases. CASE PRESENTATION: This report described an unusual case of jejunum metastasis from primary pulmonary RMS causing intussusception in a 75-year-old man. The patient consulted for 2 weeks of continuous dyspnea. Chest computed tomography (CT) demonstrated a large mass involving the left lower lobe. Transthoracic biopsy confirmed the existence of pleomorphic RMS. Immunohistochemical studies showed positive findings about desmin and MyoD1. The results of gastroscopy, colonoscopy and abdominal CT were all negative. Positron emission tomography/CT demonstrated a fluorodeoxyglucose-reactive large lesion in the left lower lobe without metastatic lesions. The patient received synchronous chemoradiotherapy. After 9 months, the patient presented with intermittent upper abdominal pain with nausea and vomiting. CT showed small bowel dilatation secondary to intussusception. The patient subsequently received laparotomy, and the intussuscepted small bowel segment was resected. Histological examination revealed pleomorphic RMS involving the mucosa, submucosa, and muscular tissues. CONCLUSIONS: RMS is highly aggressive and metastatic. The metastatic disease can rapidly progress to cause subsequent complications. The possibility of small bowel metastasis should be considered, although it is extremely rare.

MicroRNA-31 triggers G2/M cell cycle arrest, enhances the chemosensitivity and inhibits migration and invasion of human gastric cancer cells by downregulating the expression of zeste homolog 2 (ZH2).

Gastric cancer is the second most leading cause of cancer related mortality across the world over. Although the incidence of GC has declined to some extent but it is still the fourth highly diagnosed cancer across the world. GC generally remains undiagnosed till advanced stages due to unavailability of biomarkers and when diagnosed it becomes difficult to manage due to the lack of therapeutic targets and efficient chemotherapy. There are concrete evidences suggesting that miRNAs may prove important therapeutic targets for the treatment of devastating diseases such as cancer. The study was designed to investigate the tumor suppressive role of miR-31 via regulation of zeste homolog 2 (ZH2). It was found that miR-31 is significantly downregulated in GC cell lines. Overexpression of miR-31 causes significant (P < 0.05) decrease in the viability and colony formation via initiation of G2/M cell cycle arrest of the AGS cancer cells. Moreover, miR-31 overexpression also enhanced the chemosensitivity of miR-31 to the anticancer drug 5-fluorouracil. In silico analysis together with dual luciferase reporter assay indicated zeste homolog 2 (ZH2) to be the potential target of miR-31 in AGS cells. Investigation of ZH2 expression in GC cell lines showed it to be significantly (P < 0.05) upregulated. Nonetheless, overexpression of miR-31 in AGS cells resulted in the suppression of ZH2 expression. Additionally, silencing of ZH2 in the AGS cells also caused inhibition of AGS cell proliferation and colony formation via G2/M arrest. Moreover, overexpression of ZH2 could at least partially reverse the tumor suppressive effects of miR-31 indicating direct involvement of ZH2 in the miR-31 mediated inhibitory effects on AGS cell proliferation. Finally, miR-31 overexpression caused significant (P < 0.05) inhibition of the migration and invasion of the AGS gastric cancer cells. The overexpression of miR-31 also caused downregulation of mesenchymal markers (Vimentin and N-cadherin) and upregulation of epithelial marker (E-cadherin) protein expression was in AGS cells. It is therefore concluded that miR-31 acts as a tumor suppressor and may prove essential in the treatment of GC.

miR-557 inhibits the proliferation and invasion of pancreatic cancer cells by targeting EGFR.

Deregulation of microRNA has been suggested as a critical event in pancreatic cancer development and progression. Thus far, very little is known about the role of miR-557; therefore, the goal of this study was to investigate the potential role of miR-557 in pancreatic cancer. In the present study, we discovered that miR-557 expression was lowered in cancerous pancreatic tissue samples relative to non-cancerous adjacent controls, and when miR-557 was overexpressed we found that this promoted the apoptotic death of pancreatic cancer cells, suppressing their proliferation, invasion, and migration. Using western blotting and luciferase reporter assays, we further found evidence that this miRNA may directly suppress expression of the epidermal growth factor receptor via suppressing its translation through 3'-UTR binding. When EGFR was overexpressed in our pancreatic cancer cells, this was sufficient to reverse the effects of miR-557 inhibition. In summary, miR-557 acts as a tumor suppressor in pancreatic cancer cells, impairing their ability to grow and invade surrounding tissues due at least in part to EGFR inhibition. Harnessing this targeting of EGFR via this miRNA may therefore be a viable strategy useful for patient suffering from this deadly disease.

Controlled Self-Assembly of Multiple-Responsive Superamphiphilc Polymers Based on Host-Guest Inclusions of a Modified PEG with ß-Cyclodextrin.

Superamphiphilic polymers (SAPs) constructed by host-guest inclusion can self-assemble into various nanostructures in solution, which can find applications in many fields such as nanodevices, drug delivery, and template synthesis. Herein, we report the controlled self-assembly of multiple-responsive SAP based on a selective host-guest inclusion of ß-cyclodextrin (ß-CD) with a modified poly(ethylene glycol) (PEG) (FcC11AzoPEG) consisting of a ferrocene (Fc) end group, a C11 alkyl chain, an azobenzene (Azo) block, and a poly(ethylene glycol)methyl ether (PEG) chain. These SAPs can self-assemble into interesting nanostructures in water upon exposure to different stimuli because ß-CD can be selectively included with different guests, such as Fc, Azo, and C11 alkyl chain, under different stimuli. The inclusion complex of Fc with ß-CD (Fc@ß-CD SAP) can form nanowire micelles in aqueous solution. The nanowire micelles can be transformed into spindle micelles with the addition of oxidant because the majority of ß-CDs dissociated from the complex Fc@ß-CD SAP due to a conversion of Fc to Fc+ and will preferentially include with Azo group to form another dominant inclusion complex (Azo@ß-CD SAP). After UV irradiation, the spindle micelles can be further transformed into spherical micelles because most of ß-CDs are excluded from the complex Azo@ß-CD SAP due to a trans- to cis-Azo conversion and then form a dominant inclusion complex with C11 alkyl chains (C11@ß-CD SAP). This work not only demonstrates the selective host-guest inclusion of stimuli-responsive groups modified PEG with ß-CD but also provides a useful approach for construction of diverse morphologies.