Photonic-assisted multi-format dual-band microwave signal generator without background noise.

We report a photonic approach to generate background-free multi-format dual-band microwave signals based on a single modulator, which is suitable for high-precision and fast detection of radars in complex electromagnetic environments. By applying different radio-frequency signals and electrical coding signals to the polarization-division multiplexing Mach-Zehnder modulator (PDM-MZM), the generation of dual-band dual-chirp signals or dual-band phase-coded pulse signals centered at 10 and 15.5 GHz is experimentally demonstrated. Furthermore, by choosing an appropriate fiber length, we verified that the generated dual-band dual-chirp signals are not affected by chromatic-dispersion induced-power fading (CDIP); meanwhile, by autocorrelation calculations, we got high pulse compression ratios (PCRs) of 13 of the generated dual-band phase-encoded signals, showing that the generated phase-encoded signals can be emitted directly without extra pulse truncation operation. The proposed system features a compact structure, reconfigurability and polarization independence, which is promising for multi-functional dual-band radar systems.

Photonic-assisted frequency downconverter with self-interference cancellation and fiber dispersion elimination based on stimulated Brillouin scattering.

A photonic-assisted frequency downconverter with self-interference cancellation and fiber dispersion elimination is proposed for in-band full-duplex (IBFD) radio-over-fiber (ROF) systems based on stimulated Brillouin scattering. In this work, a dual-polarization Mach-Zehnder modulator (DPol-MZM) is employed to cancel the self-interference signal in the optical domain, thus the proposed system has a large operation bandwidth without the limitation of the electrical bottleneck. Meanwhile, a widely tunable microwave photonic filter (MPF) based on stimulated Brillouin scattering (SBS) is constructed to perform carrier-suppressed single-sideband modulation of LO. Therefore, the proposed photonic frequency downconverter is naturally free from fiber dispersion. Furthermore, thanks to the characteristics of the SBS-based MPF, such as large out-of-band rejection ratio, high resolution and wideband tunability, the proposed system has a high flexibility and downconversion efficiency, which is of great significance for IBFD ROF systems.

Risk factors for intracranial infection after craniotomy: A case-control study.

BACKGROUND: Intracranial infection, serving as a severe postoperative infection after craniotomy, poses significant problems for patients' outcomes. OBJECTIVE: To explore risk factors for intracranial infection after craniotomy. METHODS: A total of 2,174 patients who underwent craniotomy from 1 May 2018 to 30 June 2019 were retrospectively studied. Finally, 196 patients with intracranial infections were classified as case group, and 392 patients randomly selected from patients without intracranial infection were classified as control group. Demographic, clinical, laboratory, microbiological, and antimicrobial data were systemically recorded. The characteristics, pre- and postoperative variables, and other variables were evaluated as risk factors for intracranial infection by univariate analysis and binary logistic regression model. RESULTS: There was no significant difference in terms of demographics between two groups, except for gender, hypertension, length of stay (LOS), intraoperative blood loss, tumor, and trauma surgery. The independent risk factors were male, age ≤45, hypertension, tumor surgery, surgery in autumn (compared with spring), surgical duration ≥4 hr, intraoperative blood loss ≥400 ml, and postoperative oral infection, coma, and serum RBC > normal value. Trauma surgery (p < .001, OR = 0.05, 95% CI: 0.017-0.144) was an independent protective factor (p < .05, OR < 1) for intracranial infection. All 196 patients in the case group submitted specimens for cerebrospinal fluid (CSF) cultures, and 70 (35.71%) patients had positive results. Gram-positive pathogens predominated (59 cases, 84.28%). Staphylococcus were the most common causative pathogens, and fully resistant to aztreonam, cefazolin, and benzylpenicillin, but not resistant to linezolid and minocycline. CONCLUSION: Identifying the risk factors, pathogens, and pathogens' antibiotic resistance for intracranial infection after craniotomy plays an important role in the prognosis of patients.

Effect of pre-surgery assessments on the prognosis of patients received extracranial-intracranial bypass surgery.

BACKGROUND: Extracranial-intracranial (EC-IC) bypass surgery has been used to improve the conditions of cerebral ischemia symptoms for selected patients resulting from diverse complications such as stroke and atherosclerotic disease. However, several clinical trials showed EC-IC bypass surgery failed to prevent recurrent ischemic stroke in certain patients. OBJECTIVE: Our clinical trial aimed to investigate whether there is a correlation between pre-surgery assessments and prognosis of patients received EC-IC bypass operation. METHODS: We divided all patients into 4 groups according to their compensatory stages of cerebral ischemia. The values of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP), and oxygen extraction fraction (OEF) were obtained by computed tomography perfusion (CTP), single photon emission computed tomography (SPECT), and positron emission tomography (PET) at different time points before and after EC-IC bypass surgery. We assessed the correlations between the compensatory stage with modified Rankin scale (mRS) scores, survival rates, stroke and TIA incidences over the 12 months after surgery. RESULTS: Patients with normal CBF, normal or increased CBV, and normal OEF tended to have a better prognosis after the EI-CI bypass operation than patients with abnormal CBF, CBV and OEF. However, patients with abnormal CBF and CBV, and increased OEF showed elevated mRS, less survival rates, and higher stroke and TIA incidences over the 12 months after surgery, compared to the groups with normal CBF, CBV and OEF. CONCLUSIONS: Our results suggest that a defined compensatory stage of cerebral ischemia might be useful for the prognosis of patients receiving EI-CI bypass surgery.

Phosphoribosylpyrophosphate Synthetase 1 Knockdown Suppresses Tumor Formation of Glioma CD133+ Cells Through Upregulating Cell Apoptosis.

Relapse is the main cause of mortality in patients with glioblastoma multiforme (GBM). Treatment options involve surgical resection followed by a combination of radiotheraphy and chemotherapy with temozolomide. Several genes and genetic pathways have been identified to contribute to therapeutic resistance, giving rise to recurrence of the malignancy. In the last decades, glioma stem cells (GSCs) with the capacity of self-renewal have been demonstrated to maintain tumor propagation and treatment resistance. Here, we isolated CD133-positive (CD133+) and CD133-negative (CD133-) cells from glioblastoma U98G and U87MG cell lines. The role of phosphoribosylpyrophosphate synthetase 1 (PRPS1), which catalyzes the first step of the synthesis of nucleotide, in proliferation and apoptosis was investigated. We found that PRPS1 had a remarkable effect on cell proliferation and sphere formation in both CD133+ and CD133- cells. Compared to CD133- cells, CD133+ cells exhibited more significant results in cell apoptosis assay. CD133+ T98G and U87MG cells were used in xenograft mouse model of tumor formation. Interestingly, the mice implanted with PRPS1 knockdown T98G or U87MG stem cells exhibited prolonged survival time and reduced tumor volume. By immunostaining caspase-3 in tumor tissues of these mice, we demonstrated that the apoptotic activities in tumor cells were positively correlated to the survival time but negatively correlated to PRPS1 expression. Our results indicate that PRPS1 plays an important role in proliferation and apoptosis in GSCs and provide new clues for potential PRPS1-targeted therapy in GBM treatment.