Factors Affecting Selenium Status in Infants on Parenteral Nutrition Therapy.

INTRODUCTION: Selenium is an essential micronutrient that must be supplemented in infants and young children on exclusive parenteral nutrition (PN). We examined selenium status and clinical factors associated with a deficiency in infants on PN. METHODS: This was a retrospective cohort study of pediatric patients receiving PN with routine monitoring of selenium status. Deficiency was diagnosed using age-based norms of plasma selenium status. Associations between selenium deficiency and the following clinical factors were examined: birthweight status: extremely low birthweight (ELBW) versus very low birthweight (VLBW) versus low birthweight (LBW) versus normal birthweight (NBW), serum albumin status, presence of cholestasis, and co-administration of enteral feeds. RESULTS: A total of 42 infants were included with gestational age [median (interquartile range)] 28 weeks (25,34). The prevalence of selenium deficiency was 80% and the prevalence of albumin deficiency was 87.5%. The odds of selenium deficiency were higher in ELBW infants (odds ratio = 17.84, 95% confidence interval [4.04-78.72], P < 0.001) and VLBW infants (odds ratio = 16.26, 95% confidence interval [1.96-135.04], P < 0.001) compared to NBW infants. The odds of selenium deficiency were 5-fold higher in patients with low serum albumin (odds ratio = 5.33, 95% confidence interval [1.39-20.42], P = 0.015). There were no associations seen between selenium status and presence of cholestasis or co-administration of enteral feeds. CONCLUSION: In this cohort of infants on PN therapy, the main clinical factors associated with selenium deficiency were presence of hypoalbuminemia and history of ELBW or VLBW. These findings support dual measurement of serum albumin and serum selenium to improve interpretation of selenium status.

Manifestations of Cow's-Milk Protein Intolerance in Preterm Infants.

OBJECTIVES: Cow's-milk protein intolerance (CMPI) is poorly recognized in preterm infants. This study examined the clinical events that preceded the diagnosis of CMPI in preterm infants. METHODS: This was a retrospective study of infants in a level-III neonatal intensive care unit of those who received parenteral nutrition (PN) support during a 12-month period. Parameters assessed included birth weight (g), diagnosis, duration and frequency on PN, type of enteral feeds at initiation, and achievement of enteral autonomy. CMPI was diagnosed based on persistent feeding intolerance that resolved after change of feeds from intact protein to a protein hydrolysate or crystalline amino acid formula. RESULTS: Three hundred forty-eight infants with birth weight (median/range) 1618 g (425-5110) received PN. Fifty-one (14%) infants required multiple courses of PN, and 19 of 348 (5%) were diagnosed with CMPI. The requirement for multiple courses on PN versus single course was associated with a high likelihood of CMPI: 14 of 51 versus 5 of 297, P < 0.001. Nine of the 14 infants identified with CMPI were initially diagnosed with necrotizing enterocolitis (NEC) after a median duration of 22 days (19-57) on intact protein feeds. After recovery from NEC, they had persistent feeding intolerance including recurrence of "NEC-like illness" (N = 3) that resolved after change of feeds to a protein hydrolysate or crystalline amino acid formula. CONCLUSIONS: The requirement for multiple courses of PN because of persistent feeding intolerance after recovery from NEC and recurrence of "NEC-like illness" may be a manifestation of CMPI in preterm infants.

Super-High-Frequency Low-Loss Sezawa Mode SAW Devices in a GaN/SiC Platform.

This paper presents a comprehensive study of the performance of Sezawa surface acoustic wave (SAW) devices in SweGaN QuanFINE® ultrathin GaN/SiC platform, reaching frequencies above 14 GHz for the first time. Sezawa mode frequency scaling is achieved due to the elimination of the thick buffer layer typically present in epitaxial GaN technology. Finite element analysis (FEA) is first performed to find the range of frequencies over which the Sezawa mode is supported in the grown structure. Transmission lines and resonance cavities driven with Interdigital Transducers (IDTs) are designed, fabricated, and characterized. Modified Mason circuit models are developed for each class of devices to extract critical performance metrics. We observe a strong correlation between measured and simulated dispersion of the phase velocity (vp) and piezoelectric coupling coefficient (k2). Maximum k2 of 0.61% and frequency-quality factor product (f.Qm) of 6×1012 s-1 are achieved for Sezawa resonators at 11 GHz, with a minimum propagation loss of 0.26 dB/λ for the two-port devices. Sezawa modes are observed at frequencies spanning up to 14.3 GHz, achieving a record high in GaN microelectromechanical systems (MEMS) to the best of the authors' knowledge.

Analysis and Modeling of an 11.8 GHz Fin Resonant Body Transistor in a 14 nm FinFET CMOS Process.

In this work, a compact model is presented for a 14-nm CMOS-based fin resonant body transistor (fRBT) operating at a frequency of 11.8 GHz and targeting radio frequency (RF) generation/filtering for next-generation radio communication, clocking, and sensing applications. Analysis of the phononic dispersion characteristics of the device, which informs the model development, shows the presence of displacement component coupling due to the periodic nature of the back-end-of-line (BEOL) metal phononic crystal (PnC). An eigenfrequency-based extraction process, applicable to resonators based on electrostatic force transduction, has been used to model the resonance cavity. Augmented forms of the Berkeley short channel IGFET model (BSIM)-common multigate (CMG) model for FinFETs are used to model the drive and sense transistors in the fRBT. This model framework allows easy integration with the foundry-supplied process design kits (PDKs) and circuit simulators while being flexible toward change in transduction mechanisms and device architecture. Ultimately, the behavior is validated against RF measured data for the fabricated fRBT device under different operating conditions, leading to the demonstration of the first complete model for this class of resonant device integrated seamlessly in the CMOS stack.

The resonant body transistor.

This paper introduces the resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body. Combining the benefits of FET sensing with the frequency scaling capabilities and high quality factors (Q) of internal dielectrically transduced bar resonators, the resonant body transistor achieves >10 GHz frequencies and can be integrated into a standard CMOS process for on-chip clock generation, high-Q microwave circuits, fundamental quantum-state preparation and observation, and high-sensitivity measurements. An 11.7 GHz bulk-mode RBT is demonstrated with a quality factor Q of 1830, marking the highest frequency acoustic resonance measured to date on a silicon wafer.

Switchable Transducers in GaN MEMS Resonators: Performance Comparison and Analysis.

This work presents a comprehensive comparison of switchable electromechanical transducers in an AlN/GaN heterostructure toward the goal of reconfigurable RF building blocks in next-generation ad hoc radios. The transducers' inherent switching was achieved by depleting a 2D electron gas (2DEG) channel, allowing an RF signal launched by interdigital transducers (IDTs) to effectively excite the symmetric (So) Lamb mode of vibration in the piezoelectric membrane. Different configurations for applying DC bias to the channel for electromechanical actuation in the piezoelectric are discussed. Complete suppression of the mechanical mode was achieved with the transducers in the OFF state. Equivalent circuit models were developed to extract parameters from measurements by fitting in both ON and OFF states. This is the first time that an extensive comparative study of the performance of different switchable transducers in their ON/OFF state is presented along with frequency scaling of the resonant mode. The switchable transducer with Ohmic IDTs and a Schottky control gate showed superior performance among the designs under consideration.

A tunable ferroelectric based unreleased RF resonator.

This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator, integrated seamlessly in Texas Instruments' 130 nm Ferroelectric RAM (FeRAM) technology. The designs presented here are monolithically integrated in solid-state CMOS technology, with no post-processing or release step typical of other MEMS devices. An array of FeCAPs in this complementary metal-oxide-semiconductor (CMOS) technology's back-end-of-line (BEOL) process were used to define the acoustic resonance cavity as well as the electromechanical transducers. To achieve high quality factor (Q) of the resonator, acoustic waveguiding for vertical confinement within the CMOS stack is studied and optimized. Additional design considerations are discussed to obtain lateral confinement and suppression of spurious modes. An FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and Q of 1012. This gives a frequency-quality factor product f ⋅ Q = 7.11 × 1 0 11 which is 1.6× higher than the most state-of-the-art Pb(Zr,Ti)O3 (PZT) resonators. Due to the ferroelectric characteristics of the FeCAPs, transduction of the resonator can be switched on and off by adjusting the electric polarization. In this case, the resonance can be turned off completely at ±0.3 V corresponding to the coercive voltage of the constituent FeCAP transducers. These novel switchable resonators may have promising applications in on-chip timing, ad-hoc radio front ends, and chip-scale sensors.

Effects of Chromium on Glucose Tolerance in Infants Receiving Parenteral Nutrition Therapy.

OBJECTIVES: Early hyperglycemia is prevalent in preterm infants receiving parenteral nutrition (PN) therapy. Chromium improves glucose tolerance by potentiating the action of insulin. Therefore, we hypothesized that supplementing PN with chromium would improve glucose tolerance and PN calorie delivery in infants during the first week of life. METHODS: We collected data on neonates receiving PN initiated at birth with chromium (0.2 mcg/kg/d) started either on days 5-7 (group A) vs day 1 (group B) on PN and compared glucose tolerance and PN calorie administration over the first week of life. RESULTS: For similar mean serum glucose concentrations between group A (n = 348) and B (n = 358) (107 ± 48 vs 111 ± 52 mg/dL, P = .3), infants in group B tolerated higher glucose infusion rates and received more PN calories during the first week of life: 8.4 ± 2 vs 8 ± 2 mg/kg/min (P < .001) and 74.8 ± 23 vs 71.5 ± 12 kcal/kg/d (P = .017), respectively. The difference in calories delivered was more pronounced among very low birth weight (VLBW) infants compared with infants >1500 g: 76.5 ± 14 vs 72.4 ± 11 kcal/kg/d (P = .009) and 73.8 ± 27 vs 70.3 ± 12 kcal/kg/d (P = .079), respectively. CONCLUSIONS: PN chromium supplementation resulted in better glucose tolerance and calorie delivery during the first week of life, especially in VLBW infants. This supports chromium's essential role in enhancing glucose tolerance during PN therapy in VLBW infants at risk for early hyperglycemia.

Internal dielectric transduction: optimal position and frequency scaling.

We propose the optimal design for "internal dielectric transduction" of longitudinal bulk mode resonators. This transduction increases in efficiency as the dielectric thickness approaches half the acoustic wavelength. With dielectric films at positions of maximum strain (minimum displacement) in the resonator, 60 GHz resonators are proposed with 50 Omega motional impedance.

Bulk mode piezoresistive thermal oscillators: time constants and scaling.

This paper presents design and analysis for engineering the thermal and mechanical time constants of piezoresistive thermal oscillators. The optimal design is obtained by minimizing the threshold current density required to initiate self-sustained oscillations. Optimizing the oscillator geometry is of extreme practical importance given that the threshold current densities (GA/m(2)) are close to the breakdown current densities observed in silicon. The equivalent circuit model of the oscillator is used along with the lumped thermal, mechanical, and piezoresistive parameters to calculate the threshold current density of the oscillator. The optimal ratio of the thermal and mechanical time constants is found to be √3 for bulkmode oscillators where the in-plane dimensions control the mechanical resonant frequency. The final frequency of oscillations is obtained as a function of the mechanical resonant frequency, quality factor (Q), and the ratio of the time constants. Results show that scaling the dimension (or frequency) has a weak sub-linear effect on the oscillator performance. Finally, we compare different bulk modes, based on the calculated threshold dc currents for a 1-GHz oscillator.

Temperature coefficient of frequency modeling for CMOS-MEMS bulk mode composite resonators.

CMOS-MEMS resonators, which are promising building blocks for achieving monolithic integration of MEMS structure, can be used for timing and filtering applications, and control circuitry. SiO2 has been used to make MEMS resonators with quality factor Q > 10(4), but temperature instability remains a major challenge. In this paper, a design that uses an embedded metal block for temperature compensation is proposed and shows sub-ppm temperature stability (-0.21 ppm/K). A comprehensive analytical model is derived and applied to analyze and optimize the temperature coefficient of frequency (TCF) of the CMOS-MEMS composite material resonator. Comparison with finite element method simulation demonstrates good accuracy. The model can also be applied to predict and analyze the TCF of MEMS resonators with arbitrary mode shape, and its integration with simulation packages enables interactive and efficient design process.