?? ????? ??????? ??? ????????????? ?????? ??????? ???? ??????? ????????????? ??? ???????? ?? 1978 ??? ?? ????? ?????? ???? ??? ?? 1980. ??????, ??????????? ??? 2020, ??????? 17 ???? ??? ??? ??????? 25 ?????????. ?? 1995 ?? ????? ??????????? ??? ????????? ?????? ???? ??????? ??? ??????, ???? ????????????????? ??? ???????? ??? ?????? ??? ????????? ?????? 8 ??? ??????????? ??? ??? ???? ??? ?????????. ?? ???????? ??? ????? ?????? ??? ????? ????????? ?? ????? ??????? ???? ?? ?? ????? ????????? ??????????? [1] ??? ?? ?????? ??????????? ???? ???????? [2], ???????? ??? Univ. of Southern California (???).

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서울 소재 7개 종합병원 암환자들의 보완대체요법 이용양상

Magnesium-based bioceramics in orthopedic applications.

In the search for more ideal bone graft materials for clinical application, the investigation into ceramic bone cements or bone void filler is ongoing Calcium phosphate-based materials have been widely explored and implemented for medical use in bone defect repair Such materials are an excellent choice because the implant mimics the natural chemistry of mineralized bone matrix and in injectable cement form, can be implemented with relative ease However, of the available calcium phosphate cements, none fully meet the ideal standard, displaying low strengths and acidic setting reactions or slow setting times, and are often very slow to resorb in vivo The study of magnesium phosphates for bone cements is a relatively new field compared to traditional calcium phosphate bone cements Although reports are more limited, preliminary studies have shown that magnesium phosphate cements (MPC) may be a strong alternative to calcium phosphates for certain applications The goal of the present publication is to rev

Magnesium Phosphate Cement Systems for Hard Tissue Applications: A Review

Brushite cements differ from apatite-forming compositions by consuming a lot of water in their setting reaction whereas apatite-forming cements consume little or no water at all. Only such cement systems that consume water during setting can theoretically produce near-zero porosity ceramics. This study aimed to produce such a brushite ceramic and investigated whether near elimination of porosity would prevent a burst release profile of incorporated antibiotics that is common to prior calcium phosphate cement delivery matrices. Through adjustment of the powder technological properties of the powder reactants, that is particle size and particle size distribution, and by adjusting citric acid concentration of the liquid phase to 800 mM, a relative porosity of as low as 11% of the brushite cement matrix could be achieved (a 60% reduction compared to previous studies), resulting in a wet unprecompacted compressive strength of 52 MPa (representing a more than 100% increase to previously reported results) with a workable setting time of 4.5 min of the cement paste. Up to 2 wt.% of vancomycin and ciprofloxacin could be incorporated into the cement system without loss of wet compressive strength. It was found that drug release rates could be controlled by the adjustable relative porosity of the cement system and burst release could be minimized and an almost linear release achieved, but the solubility of the antibiotic (vancomycin > ciprofloxacin) appeared also to be a crucial factor.

High strength resorbable brushite bone cement with controlled drug releasing capabilities

Up to now magnesium phosphate cements are mainly being utilized in wastewater treatment due to their adsorptive properties. Recently they also have been shown to have a high potential as degradable biocements for application as replacement materials for bone defects. In comparison to degradable calcium phosphate cements they have the advantage of setting at neutral pH, which is favorable in biological environment. In this study two parameters of the cement composition, namely powder-to-liquid ratio (PLR) and citrate content, were varied in order to optimize the injectability properties of the cement paste and the mechanical properties of the reaction product. These properties were determined by means of testing setting time and temperature, paste viscosity, and injectability as well as phase composition and compressive strength of the set cements. Best results were obtained, when the cements were prepared with a PLR of 2.5 and a binder liquid consisting of an aqueous solution of 3 mol/l diammonium hydrogen phosphate and 0.5 mol/l diammonium citrate.

Injectability and mechanical properties of magnesium phosphate cements

Bone loss due to accidents or tissue diseases requires replacement of the structure by either autografts, allografts, or artificial materials. Reactive cements, which are based on calcium phosphate chemistry, are commonly used in nonload bearing areas such as the craniofacial region. Some of these materials are resorbed by the host under physiological conditions and replaced by bone. The aim of this study was to test different calcium and magnesium cement composites in vitro for their use as bone substitution material. Phase composition of calcium deficient hydroxyapatite (Ca(9) (PO(4) )(5) HPO(4) OH), brushite (CaHPO(4) ·2H(2) O), and struvite (MgNH(4) PO(4) ·6H(2) O) specimens has been determined by means of X-ray diffraction, and compressive strength was measured. Cell growth and activity of osteoblastic cells (MG 63) on the different surfaces was determined, and the expression of bone marker proteins was analyzed by western blotting. Cell activity normalized to cell number revealed higher activity of the osteoblasts on brushite and struvite when compared to hydroxyapatite and also the expression of osteoblastic marker proteins was highest on brushite scaffolds. While brushite sets under acidic conditions, formation of struvite occurs under physiological pH, similar to hydroxyapatite cements, providing the possibility of additional modifications with proteins or other active components.

Effect of cold‐setting calcium‐ and magnesium phosphate matrices on protein expression in osteoblastic cells

We present resonant tunneling diode-photodetectors (RTD-PDs) with GaAs0.15Sb0.85/AlAs0.1Sb0.9 double barrier structures combined with an additional quaternary Ga0.64In0.36As0.33Sb0.67 absorption layer covering the fingerprint absorption lines of various gases in the mid-infrared wavelength spectral region. The absorption layer cut-off wavelength is determined to be 3.5 μm, and the RTD-PDs show peak-to-valley current ratios up to 4.3 with a peak current density of 12 A/cm−2. The incorporation of the quaternary absorption layer enables the RTD-PDs to be sensitive to illumination with light up to the absorption lines of HCl at 3395 nm. At this wavelength, the detector shows a responsivity of 6.3 mA/W. At the absorption lines of CO2 and CO at 2004 nm and 2330 nm, respectively, the RTD-PDs reach responsivities up to 0.97 A/W. Thus, RTD-PDs pave the way towards high sensitive mid-infrared detectors that can be utilized in tunable laser absorption spectroscopy.

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Mid-infrared GaSb-based resonant tunneling diode photodetectors for gas sensing applications

We present room temperature resonant tunneling of GaSb/AlAsSb double barrier resonant tunneling diodes with pseudomorphically grown prewell emitter structures comprising the ternary compound semiconductors GaInSb and GaAsSb. At room temperature, resonant tunneling is absent for diode structures without prewell emitters. The incorporation of Ga0.84In0.16Sb and GaAs0.05Sb0.95 prewell emitters leads to room temperature resonant tunneling with peak-to-valley current ratios of 1.45 and 1.36, respectively. The room temperature operation is attributed to the enhanced Γ-L-valley energy separation and consequently depopulation of L-valley states in the conduction band of the ternary compound emitter prewell with respect to bulk GaSb.

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Room temperature operation of GaSb-based resonant tunneling diodes by prewell injection

We investigate the electronic transport properties of GaSb/AlAsSb double barrier resonant tunneling diodes with pseudomorphically grown ternary GaAsxSb1-x emitter prewells over a broad temperature range. At room temperature, resonant tunneling is observed and the peak-to-valley current ratio (PVCR) is enhanced with the increasing As mole fraction from 1.88 (GaAs0.07Sb0.93 prewell), to 2.08 (GaAs0.09Sb0.91 prewell) up to 2.36 (GaAs0.11Sb0.89 prewell). The rise in PVCR is attributed to an enhanced carrier density at the Γ-valley within the emitter prewell. On the contrary at cryogenic temperatures, increasing the As mole fractions reduces the PVCR. At a temperature of T=4.2 K, reference samples without incorporation of an emitter prewell containing As show PVCRs up to 20.4. We attribute the reduced PVCR to a degraded crystal quality of the resonant tunneling structure caused by As incorporation and subsequently an enhanced defect scattering at the interfaces.

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Georg Knebl

Papers

Effect of cold‐setting calcium‐ and magnesium phosphate matrices on protein expression in osteoblastic cells

Mid-infrared GaSb-based resonant tunneling diode photodetectors for gas sensing applications

Room temperature operation of GaSb-based resonant tunneling diodes by prewell injection

GaSb/AlAsSb resonant tunneling diodes with GaAsSb emitter prewells

Optical Mapping of Nonequilibrium Charge Carriers