Cluster-Based Cell-Free Massive MIMO Systems: A Novel Framework to Enhance Spectral Efficiency with Low Complexity

The issue of diminished spectral efficiency (SE) of the downlink (DL) transmission in distributed cell-free massive MIMO (CF-mMIMO) systems poses a significant challenge in terms of user equipment (UE) performance when compared to their centralized CF-mMIMO counterparts. The primary root cause of this issue can be attributed to the reduced efficacy of distributed precoders, which are devised using local channel state information (CSI) in distributed systems. This reduced efficacy becomes particularly pronounced in terms of interference mitigation when compared to centralized precoders. To address this issue, this paper proposes a novel architectural framework for CF-mMIMO systems, referred to herein as the "cluster-based structure." Within this innovative structure, a hybrid amalgamation of centralized and distributed configurations is employed, complemented by the introduction of a unique cluster arrangement for the access points (APs) within the network. In this design, the CSI of APs within each cluster is collectively shared within a local processor unit. Consequently, by harnessing this enhanced repository of local channel information, local precoders are formulated, which facilitate more effective interference mitigation with reduced computational complexity compared to the centralized approach. This approach ultimately results in a significantly augmented SE when contrasted with the distributed architecture. The simulation results unequivocally demonstrate that within the cluster-based framework, the optimal SE for the network is attained when utilizing four clusters in conjunction with the MMSE precoding technique, leading to a notable reduction in computational complexity exceeding 85%. Importantly, this approach surpasses the SE performance of the centralized structure

Evaluation of A Post-Treatment Follow-Up Program in Patients with Oral Squamous Cell Carcinoma

Objectives The duration and the frequency of follow-up after treatment of oral squamous cell carcinoma are not standardized in the current literature. The purpose of this study was to evaluate our local standard post-treatment and follow-up protocol. Materials and methods Overall, 228 patients treated curatively from 01/2006 to 07/2013 were reviewed. To evaluate the follow-up program, data on the secondary event were used. To determine risk groups, all patients with tumor recurrence were specifically analyzed. Relapse-free rate were estimated by the Kaplan-Meier product limit method. The chi-square test was used to identify independent risk factors for tumor relapse. Results In total, 29.8 % patients had a secondary event. The majority of the relapse cases (88.2 %) were detected within 2 years postoperatively, 61.8 % of them within the first year. Most events were local recurrences (34.7 %). UICC-stage IV was significantly associated with tumor recurrence (p = 0.001). Gender (p = 0.188), age (p = 0.195), localization (p = 0.739), T-stage (p = 0.35), N-stage (p = 0.55), histologic grade (p = 0.162), and tobacco and alcohol use (p = 0.248) were not significantly associated with tumor recurrence. Patients with positive neck nodes relapsed earlier (p = 0.011). The majority of relapses (86.3 %) were found in asymptomatic patients at routine follow-up. Conclusions The results of this study suggest an intensified follow-up within the first 2 years after surgery. Clinical relevance Given the higher relapse rate of patients exhibiting an UICC-stage IV and/or positive neck nodes, it seems to be from special interest to perform in this group a risk-adapted follow-up with monthly examinations also in the second year

Self-propagating reactive Al/Ni nanocomposites for bonding applications

Highly reactive integrated material systems have recently gained attention, as they promise a feasible tool for heterogeneous integration of micro electromechanical systems. As integrated energy sources they can be used to join heterogeneous materials without applying too much thermal stress to the whole device. An alternative approach is proposed, comprising a single layer of a reactive nanocomposite made of intermixed metal nanoparticles, instead of multilayer systems. In this study the development of the reactive nanocomposite from choice of materials through processing steps, handling and application methods are described. Eventually the results of the experiments upon the reactivity of the nanocomposites and the feasibility for bonding applications are presented. Analysis of the composites was performed by phase-analysis using x-ray diffraction and reaction propagation analysis by high-speed imaging. Composition of products was found to vary with initial particle sizes. Beside of other phases, the dominant phase was intermetallic NiAl

Longterm quality of life after oncologic surgery and microvascular free flap reconstruction in patients with oral squamous cell carcinoma

Background: Quality of life (QoL) has become increasingly important in cancer treatment. It refers to the patient’s perception of the effects of the disease and therapy, and their impact on daily functioning and general feeling of well being. Material and Methods: In this prospective study, a total of 100 patients treated at our institution, completed the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 questionnaire and the specific EORTC QLQ-H&N35 module. The questionnaires were distributed to the patients between 12 and 60 months postoperatively. Results: Global QoL score was 58.3 and mean score for functioning scale was 76.7. Fatigue (28.7 ± 26.1), followed by financial problems (27.7 ± 33.5), insomnia (26.7 ± 34.5) and pain (26.3 ± 29.9) had highest symptom score on QLQ-C30. Fatigue (r=-0.488), insomnia (r=-0.416) and pain (r =-0.448) showed highest value for significantly negative correlation to global QoL. In the H&N35 module, restriction of mouth opening (43.3 ± 38.6), dry mouth (40.7 ± 36.9), sticky saliva (37.3 ± 37.1) and eating in public (33.8 ± 31.9) were the four worst symptoms. Swallowing problem (r=-0.438), eating in public (r=-0.420) and persistent severe speech (r=-0.398) ranked as the three worst symptoms with highest value for significantly negative correlation to global QoL. Conclusions: Longterm QoL after oncologic surgery and microvascular free flap reconstruction in patients with oral cancer is satisfactory. Measuring QoL should be considered as part of the evaluation of cancer treatment

Die-Level Thinning for Flip-Chip Integration on Flexible Substrates

Die-level thinning, handling, and integration of singulated dies from multi-project wafers (MPW) are often used in research, early-stage development, and prototyping of flexible devices. There is a high demand for thin silicon devices for several applications, such as flexible electronics. To address this demand, we study a novel post-processing method on two silicon devices, an electrochemical impedance sensor, and Complementary Metal Oxide Semiconductor (CMOS) die. Both are drawn from an MPW batch, thinned at die-level after dicing and singulation down to 60 µm. The thinned dies were flip-chip bonded to flexible substrates and hermetically sealed by two techniques: thermosonic bonding of Au stud bumps and anisotropic conductive paste (ACP) bonding. The performance of the thinned dies was assessed via functional tests and compared to the original dies. Furthermore, the long-term reliability of the flip-chip bonded thinned sensors was demonstrated to be higher than the conventional wire-bonded sensors

Salivary MMP-9 in the detection of oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common malignant tumour of the oral cavity. Detection of OSCC is currently based on clinical oral examination combined with histopathological evaluation of a biopsy sample. Direct contact between saliva and the oral cancer makes measurement of salivary metalloproteinase- 9 (MMP-9) an attractive alternative. In total, 30 OSCC patients and 30 healthy controls were included in this prospective study. Saliva samples from both groups were collected, centrifuged and supernatant fluid was subjected to ELISA for assessment of MMP-9. The median salivary MMP-9 values with interquartile range (IQR) of OSCC patients and the control group were statistically analysed using the Mann-Whitney U-test. The receiver operating characteristic (ROC) curve was constructed and the area under curve (AUC) was computed. The median absorbance MMP-9 value of the OSCC group was 0.186 (IQR=0.158) and that of control group was 0.156 (IQR=0.102). MMP-9 was significantly increased in the OSCC patients than in the controls by +19.2% (p=0.008). Median values in patients with recurrence and in patients with primary event were 0.233 (IQR=0.299) and 0.186 (IQR=0.134) respectively. MMP-9 was significantly increased in patients with primary event (p=0.017) compared to controls by +19.2%. No significant increase of MMP-9 level was detected when comparing patients with recurrence and healthy controls (+49.4%; p=0.074). The sensitivity value of MMP-9 was 100% whereas the specificity value was 26.7% with AUC of 0.698. The present data indicates that the elevation of salivary levels of MMP-9 may be a useful adjunctive diagnostic tool for detection of OSCC. However, further studies are necessary to provide scientific and clinical validation

The Realization of Redistribution Layers for FOWLP by Inkjet Printing

The implementation of additive manufacturing technology (e.g., digital printing) to the electronic packaging segment has recently received increasing attention. In almost all types of Fan-out wafer level packaging (FOWLP), redistribution layers (RDLs) are formed by a combination of photolithography, sputtering and plating process. Alternatively, in this study, inkjet-printed RDLs were introduced for FOWLP. In contrast to a subtractive method (e.g., photolithography), additive manufacturing techniques allow depositing the material only where it is desired. In the current study, RDL structures for different embedded modules were realized by inkjet printing and further characterized by electrical examinations. It was proposed that a digital printing process can be a more efficient and lower-cost solution especially for rapid prototyping of RDLs, since several production steps will be skipped, less material will be wasted and the supply chain will be shortened.EC/H2020/737487/EU/(Ultra)Sound Interfaces and Low Energy iNtegrated SEnsors/SILENS

On the Feasibility of Fan-Out Wafer-Level Packaging of Capacitive Micromachined Ultrasound Transducers (CMUT) by Using Inkjet-Printed Redistribution Layers

Fan-out wafer-level packaging (FOWLP) is an interesting platform for Microelectromechanical systems (MEMS) sensor packaging. Employing FOWLP for MEMS sensor packaging has some unique challenges, while some originate merely from the fabrication of redistribution layers (RDL). For instance, it is crucial to protect the delicate structures and fragile membranes during RDL formation. Thus, additive manufacturing (AM) for RDL formation seems to be an auspicious approach, as those challenges are conquered by principle. In this study, by exploiting the benefits of AM, RDLs for fan-out packaging of capacitive micromachined ultrasound transducers (CMUT) were realized via drop-on-demand inkjet printing technology. The long-term reliability of the printed tracks was assessed via temperature cycling tests. The effects of multilayering and implementation of an insulating ramp on the reliability of the conductive tracks were identified. Packaging-induced stresses on CMUT dies were further investigated via laser-Doppler vibrometry (LDV) measurements and the corresponding resonance frequency shift. Conclusively, the bottlenecks of the inkjet-printed RDLs for FOWLP were discussed in detail.EC/H2020/737487/EU/(Ultra)Sound Interfaces and Low Energy iNtegrated SEnsors/SILENS

Hybrid alginate-protein cryogel beads: efficient and sustainable bio-based materials to purify immunoglobulin G antibodies

Antibodies present in mammal’s serum are of high relevance for therapeutic purposes, particularly in passive immunization and in the treatment of some chronic diseases. However, their recovery with high purity and yield is still compromised by the requirement of several process steps and constraint of keeping antibodies stable to not compromise their therapeutic efficiency. These challenges significantly contribute to the current high-cost of biopharmaceuticals, namely antibodies such as immunoglobulin G (IgG). Accordingly, the development of effective and sustainable purification strategies for antibodies and other biopharmaceuticals is in critical demand, while allowing to decrease economic, environmental and health cargos. Herein, bio-based and low-cost hybrid alginate-protein cryogel beads were prepared, characterized, and applied as novel adsorbent materials for the purification of IgG from human serum. It is shown that hybrid materials are more efficient than the respective alginate beads since the presence of proteins increases the materials selectivity for IgG. Several operating conditions, such as pH, adsorption time and serum concentration, were optimized to improve the recovery yield and purity of IgG. Adsorption isotherms were also determined to infer the adsorption mechanism of IgG onto the cryogel beads and to determine their maximum adsorption capacity (175 mg of IgG per g of cryogel beads). At the optimized conditions, IgG can be recovered from the hybrid materials using buffered aqueous solutions, with a purity of 80% and a recovery yield of 91%. The stability and integrity of the antibody is kept after the desorption step. Finally, the regeneration and reuse of the cryogel beads was evaluated, with no losses on the IgG adsorption performance and antibody stability. Although significant efforts have been placed on the development of novel affinity ligands to replace the standard chromatographic methods to purify IgG, this works demonstrates the potential of bio-based and low-cost hybrid materials as promising alternatives, in which proteins can be used to improve the materials selectivity.publishe