João Navarro

Basilar expansion of the human sphenoidal sinus: an integrated anatomical and computerized tomography study

Basilar expansion of the sphenoidal sinus (BESS) was studied in order to demonstrate its critical relevance in endoscopic or microscopic endonasal surgical interventions, including access to the sphenoidal sinus itself or in transsphenoidal pituitary approaches. Direct evaluation of anatomical specimens (25 dry skulls and 25 formalin-fixed hemi heads) and the use of computerized tomography (CT) (50 dry skulls and 750 patients) showed a high BESS frequency (69%). The authors considered BESS to be critical when the posterior wall of the clivus was 2-mm thick and found a high incidence of this important anatomical variation (44%). This study also evaluated the relationship between the sinonasal septa, the clivus, and the internal carotid arteries, and a considerable regularity in the location of these structures was seen. The septa were anatomically related to the internal carotid arteries in 55% and to the clivus in 33% of the cases. In conclusion, the high frequency of critical BESS here described is relevant to endoscopic or microscopic endonasal surgical interventions, including access to the sphenoidal sinus itself or in transsphenoidal pituitary approaches.

Metastability behavior of mismatched CMOS flip-flops using state diagram analysis

The effect on the metastability of the mismatch of FET parameters and load capacitances in a CMOS latch/flip-flop is analyzed. A novel method using state diagrams is proposed. On the state diagrams obtained by transient analysis of the latch, a straight line can be approximately drawn that defines two semiplanes, which precisely determine the latch final state. SPICE simulation results are shown for matched/mismatched flip-flops.

Anatomical study of the sphenopalatine foramen

UNLABELLED Anatomical variations of the sphenopalatine foramen may correspond to alterations at the arterial nasal irrigation input, which is a relevant condition to treat severe epistaxis through ligation of the sphenopalatine artery. AIM To study the sphenopalatine foramen in terms of its numeric variation and its location on the lateral nasal wall in relation to the bony ethmoidal crest of the palatine bone. MATERIALS AND METHODS The anatomical studies were carried out in 54 hemifaces. RESULTS the sphenopalatine foramen presented the following numeric variation: single (87%, or 47 specimens), double (11,1%, or 6 specimens), and triple (1.9% or one specimen); it was located at the superior nasal meatus in 81.5%, or 44 specimens; 14.8% (8 specimens) between the middle and superior nasal meatus and in the middle nasal meatus in only one case (1.9%). CONCLUSION We have been able to show a numeric variation of the SPF, its relation with the bony ethmoidal crest and its location in the superior meatus, middle meatus, and in both.

Estudo anatômico do forame esfenopalatino

Anatomical variations of the sphenopalatine foramen may correspond to alterations at the arterial nasal irrigation input, which is a relevant condition to treat severe epistaxis through ligation of the sphenopalatine artery. AIM: To study the sphenopalatine foramen in terms of its numeric variation and its location on the lateral nasal wall in relation to the bony ethmoidal crest of the palatine bone. MATERIALS AND METHODS: The anatomical studies were carried out in 54 hemifaces. RESULTS: the sphenopalatine foramen presented the following numeric variation: single (87%, or 47 specimens), double (11,1%, or 6 specimens), and triple (1.9% or one specimen); it was located at the superior nasal meatus in 81.5%, or 44 specimens; 14.8% (8 specimens) between the middle and superior nasal meatus and in the middle nasal meatus in only one case (1.9%). CONCLUSION: We have been able to show a numeric variation of the SPF, its relation with the bony ethmoidal crest and its location in the superior meatus, middle meatus, and in both.

A simple CMOS bandgap reference circuit with sub-1-V operation

A new circuit topology for bandgap reference voltage sources is proposed. The circuit works with current summation, has simple design characteristics, supports low voltage power supplies, and provides satisfactory stability, power consumption, and area. A 0.51 V reference source is designed in a 0.35-µm CMOS technology and simulated. Simulation results have shown that the circuit attains a temperature coefficient lower than 24 ppm/°C and a current consumption lower than 6.2 µA. Minimum power supply voltage is 1.0 V, for simulations using NMOS and PMOS VT0 (transistor threshold voltage) of 0.50 V and −0.69 V respectively, or 0.8 V, for simulations using NMOS and PMOS VT0 of 0.50 V and −0.50 V.

A 3.5 mW programmable high speed frequency divider for a 2.4 GHz CMOS frequency synthesizer

The implementation of a four bits programmable high speed frequency divider for a frequency synthesizer, using a 0.35 mum CMOS technology, is described. The programmable divider employs a divide-by-32/33 dual-modulus prescaler, two other counters, and the logic control necessary to operate the division. Additionally, a complete 2.4 GHz synthesizer was designed to test the divider; it includes a VCO, a phase frequency detector with charge pump, a low pass filter, buffers to increase the signal levels, and the programmable divider itself. Experimental results show that the programmable divider reached an operation frequency of 2.6 GHz with power consumption of 3.5 mW at 3.3 V power supply. The dimensions of the prescaler and the programmable divider are 77 mum times 33 mum and 198 mum times 33 mum, respectively

Surgical anatomy of the maxillary nerve in the zygomatic region

Anatomic knowledge on the zygomatic fossa is of primary importance to improve the regional anesthetic technique of the maxillary nerve. Few reports in the literature have addressed the trajectory of the maxillary nerve and its branches in this region; thus, this study aimed at presenting information about the trajectory of these nerves. Thirty human half-heads of both genders were fixed in 10% formalin and demineralized in 5% nitric acid, and the maxillary nerve was dissected since its origin on the pterygopalatine fossa until penetration into the inferior orbital fissure. It was observed that the maxillary nerve sends one to three posterior superior alveolar branches and tuberal descendent branches, which supply the soft tissue structures of the region. The posterior superior alveolar nerves are inferiorly oriented near the maxillary tuberosity, where they penetrate the alveolar canals with the posterior superior alveolar artery and send small nerve branches that continue in an extraosseous trajectory. This study found that nearly 2/3 of the trajectory of the maxillary nerve is located in the zygomatic region, with a short segment (1/3) in the pterygopalatine fossa.

A small area 8bits 50MHz CMOS DAC for bluetooth transmitter

This paper presents a small area CMOS current-steering segmented digital-to-analog converter (DAC) design used in a RF transmitter stage for 2.45GHz Bluetooth applications. The current source design strategy is based on an iterative scheme which variables are adjusted by a simple way, satisfying the requirements, minimizing power consumption and reaching the design specifications. A theoretical analysis of static-dynamic requirements and a new layout strategy of small area consumption for the current-steering DAC design is included. The DAC was designed and implemented in 0.35mm 4M2P CMOS technolyogy. Some performance results obtained through experimental test are: chip active area of only 200mm-200mm, full scale output current of 700mA at 3.3V power supply, INL=0.3LSB, DNL=0.37LSB, SFDR=58dB for output sine wave frequency of Fout = 1MHz and Fs = 50MHz sampling frequency, SFDR=52dB for Fout = 1MHz and Fs = 10MHz.

Design of an 8:1 MUX at 1.7 Gbit/s in 0.8 /spl mu/m CMOS technology

The design of an 8:1 multiplexer circuit, for SDH/SONET data transmission systems, is presented. In order to achieve maximum transmission rates, new circuits, high speed input/output converters for ECL-CMOS levels and modified true single phase clocked (TSPC) cells, as well as new techniques for clock buffer optimization, were applied. The multiplexer was implemented in a 0.8 /spl mu/m CMOS process (0.7 /spl mu/m effective length) achieved 1.7 Gbit/s rate and 42.6 /spl mu/W/MHz power consumption at 5 V. These results were compared to a previous implementation (in the same process), and to other recently published works, showing superior performances.

Design of an OTA-Miller for a 96dB SNR SC multi-bit Sigma-Delta modulator based on gm/I D methodology

This paper presents the design of an OTA-Miller amplifier of the first integrator of a Switched-Capacitor Multibit Sigma-Delta Modulator. The first integrator OTA is the most critical block in Sigma-Delta Modulator due to the high bandwidth, high Slew Rate and low noise requirements. The first integrator OTA specifications are obtained from the Sigma-Delta Modulator designing for low power consumption. The gm/ID methodology is used on the OTA design of the first integrator to reduce the power consumption. This methodology is also applied in the other OTAs of the Sigma-Delta Modulator. The Chopper technique is also implemented to reduce the input referred noise of the first integrator. The SDM with the designed OTAs using the gm/ID methodology is simulated by the Spectre simulator. Implemented in 0.18 μm CMOS technology, the SDM achieves a 96 dB SNR for 20 kHz signal bandwidth and a power consumption of 2.77 mW for a 1.8 V supply.