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High data rate coverage, security, and energy efficiency will play a key role in the continued performance scaling of next-generation mobile systems. Dense, small mobile cells based on a novel network architecture are part of the answer. Motivated by the recent mounting interest in free-space optical (FSO) technologies, this paper addresses a novel mobile fronthaul network architecture based on FSO, spread spectrum codes, and graphene modulators for the creation of dense small cells. The network uses an energy-efficient graphene modulator to send data bits to be coded with spread codes for achieving higher security before their transmission to remote units via high-speed FSO transmitters. Analytical results show the new fronthaul mobile network can accommodate up to 32 remote antennas under error-free transmissions with forward error correction. Furthermore, the modulator is optimized to provide maximum efficiency in terms of energy consumption per bit. The optimization procedure is carried out by optimizing both the amount of graphene used on the ring resonator and the modulator’s design. The optimized graphene modulator is used in the new fronthaul network and requires as low as 4.6 fJ/bit while enabling high-speed performance up to 42.6 GHz and remarkably using one-quarter of graphene only.

Abstract Background Although there are reports linking ulcerative colitis (UC) to prostate cancer (PC), those reports are of PC patients who were previously diagnosed with UC. There are no reports of the development of UC during radiotherapy. Here we describe the first case of a patient who developed UC during radiotherapy for PC. The UC progressed rapidly and required emergency surgery. Case presentation A 61-year-old Japanese man underwent a prostate biopsy at another hospital due to a high prostate-specific antigen level and was diagnosed with PC. Goserelin and bicalutamide treatment was initiated in 2019, and intensity-modulated radiotherapy (total of 60 Gy/20 Fr) was administered in 2020. Diarrhea began during the radiotherapy and bleeding began post-radiotherapy. He was admitted to another hospital 14 days after the end of the radiotherapy, and colonoscopy revealed a deep ulcer in the colon, which led to the suspicion of UC. He was transferred to our hospital, and colonoscopy showed a widespread map-like ulcer, pseudopolyposis, and very easy bleeding in the colon. We diagnosed severe UC, and it worsened rapidly with uncontrollable bleeding, which we considered an indication for surgery. Emergency surgery (a total colectomy and ileostomy creation) was performed. The specimens confirmed an extensively spreading ulcer throughout the colon. The pathological report was UC in the active phase. The postoperative course was good. Conclusions When a patient exhibits diarrhea while undergoing radiotherapy for PC, clinicians should be aware of the possibility of UC in addition to radiation colitis, and colonoscopy should be considered.

Abstract Background Small bowel obstruction (SBO) is a common postoperative complication of ulcerative colitis (UC). There have been a few recent reports of afferent limb syndrome (ALS) as a rare occurrence in cases of SBO. We present a case of ALS with recurrent SBO that was successfully managed surgically. Case presentation When this male patient was 55 years old, he underwent laparoscopy-assisted anus-preserving total proctocolectomy, the creation of a J-type ileal pouch, ileal pouch-anal canal anastomosis (IPAA), and creation of ileostomy for intractable UC. Three months later, ileostomy closure was performed. The first onset of SBO was observed 5 months after ileostomy closure. SBO occurred repeatedly, and the patient was hospitalized nine times in approximately 2 years. Each SBO was improved by non-surgical treatment. A computed tomography (CT) scan revealed that the afferent limb was narrowing and twisted, and gastrografin enema confirmed narrowing at the proximal portion of the pouch inlet. Endoscopy showed a sharp angulation at the pouch inlet. We suspected ALS and decided on a surgical policy and performed pouchopexy and ileopexy to the retroperitoneum by suturing with excision of the remaining blind end of the ileum. Endoscopy 3 days after surgery showed neither twist nor stricture in the fixed ileal pouch or the afferent limb. At the time of writing, the patient remains free of SBO symptoms. Conclusion Clinicians should consider ALS when examining a patient with recurrent intermittent SBO after IPAA surgery. When ALS is suspected, the patient is indicated for surgery such as surgical pexy.

Abstract Background The term “mesenteric inflammatory veno-occlusive disease (MIVOD)” is used to describe an ischemic injury resulting from phlebitis or venulitis that affects the bowel or mesentery in the absence of arteritis. MIVOD is difficult to diagnose because of its rarity and frequent confusion with other diseases. The incidence and etiology of MIVOD remain unclear; only a few cases have been reported. We describe a case of the successful surgical management of a patient with MIVOD with characteristic images. Case presentation A 65-year-old Japanese man visited a hospital with the chief complaint of abdominal pain in January 2018. CT showed edema and thickening of the intestinal wall from the descending colon to the rectum. The patient was admitted to the hospital. Suspected diagnoses were enteritis, ulcerative colitis, amyloidosis, vasculitis, malignant lymphoma, and venous thrombus, but no definitive diagnosis was obtained. The patient was transferred to our hospital for the treatment of stenosis (located from the descending colon to the rectum) and bowel obstruction. An emergency transverse colostomy was performed. The sigmoid colon and mesentery were too rigid and edematous to resect. Colonic hemorrhage occurred 2 weeks after the surgery. With radiology intervention, coiling for the arteriovenous fistula in the descending colon was performed, and hemostasis was obtained. A colonoscopy at 6 months post-surgery showed neither ulceration nor stenosis in the rectum, indicating that the rectum could be preserved in the next surgery. However, severe stenosis in the descending and sigmoid colon remained unchanged. Ten months after the transverse colostomy, we performed a subtotal colectomy and ileorectal anastomosis, and an ileostomy was created. The sigmoid colon and mesentery were not so rigid compared to the first surgery’s findings, and we were able to resect intestine and mesentery. Histopathology revealed phlebitis and venulitis, fibrinoid necrosis, and normal arteries, meeting the diagnostic criteria for MIVOD. Postoperatively, the patient showed no recurrence for 8 months. Conclusion Clinicians should consider MIVOD when examining a patient with intestinal ischemia. When MIVOD is suspected, the patient is indicated for surgery based on an accurate diagnosis and good prognosis.

Abstract Background Intussusception is a relatively common condition seen in children. In comparison, adult intussusception is rare and usually occurs as a complication in patients with organic diseases. It is responsible for 1% of all bowel obstructions, in most of intussusceptions a malignant tumor is involved. Herein, we present an extremely unusual case of intussusception that occurred as a complication at the site of a functional end-to-end anastomosis. Case presentation A 57-year-old female patient was diagnosed with tumors in the ascending and descending colon and was referred to our department. Laparoscopic hemicolectomy and laparoscopic descending colectomy were performed. The mechanical intestinal obstruction occurred on the 9th day postoperatively, and computed tomography scan revealed intussusception at the site of the ileocolic anastomosis. Endoscopic reduction was attempted, but the procedure was challenging. Surgery was then performed and revealed that the site of ileocolic anastomosis firmly adhered to the side wall and right retroperitoneum. However, the intestine in the oral side of the anastomosis was not fixed. Examination of the anastomotic site revealed that the ileum had passed through the anastomosis and prolapsed into the transverse colon. The ileocolic anastomosis was resected. End-to-end anastomosis was performed, and surgery was then completed. No neoplastic lesions were observed in the resected tissue of the lead point of intussusception. The postoperative clinical course was favorable, and the patient was discharged on the 11th day after the second round of surgery. Conclusions There are no reports the anastomosis is involved as part of the intussception, as observed in the present case. Intussusception should thus be considered as one of the causes of postoperative mechanical intestinal obstruction.

Abstract Background A tumor composed exclusively or predominantly of human melanin black 45 (HMB45)-positive epithelioid cells is called a perivascular epithelioid cell tumor (PEComa). We report a very rare case of a PEComa of the greater omentum. Case presentation MRI conducted to examine the orthopedic disease of the patients, a 49-year-old Japanese woman, also identified a tumor in her pelvis. A CT scan revealed a tumor mass on the right side of the pelvic floor and clear nutrient vessels originating from the splenic and celiac arteries. An omental primary tumor or accessory spleen was thus suspected, and tumor resection was performed. The tumor was a light brown solid tumor with a smooth margin, measuring 5.2 × 3.8 × 3.5 cm. Histopathologically, the tumor was composed mainly of spindle and epithelioid cells, and large and small blood vessel formation was observed. In the immunohistochemical staining, tumor cells were positive for human melanin black 45 (HMB-45) and Melan-A and partially positive for alpha-smooth muscle actin. The final diagnosis was PEComa of the greater omentum. Conclusions Although omental PEComa is very rare, it should be considered as a differential disease of an omental primary tumor.

Ultra-wideband (UWB) is a useful radio technique for sharing frequency bands between radio systems. It uses very short pulses to spread spectrum. However, there is a potential for interference between systems using the same frequency bands at close range. In some regulatory systems, interference detection and avoidance (DAA) techniques are required to prevent interference with existing radio systems. In this paper, the effect of interference on orthogonal frequency division multiplexing (OFDM) signals from pulse-based UWB is discussed, and an interference mitigation technique is proposed. This technique focuses on the pulse repetition cycle of UWB. The pulse repetition interval is set the same or half the period of the OFDM symbol excluding the guard interval to mitigate interference. These proposals are also made for direct sequence (DS)-UWB. Bit error rate (BER) performance is illustrated through both simulation and theoretical approximations.