1.95-μm strained InGaAs-InGaAsP-InP distributed-feedbackquantum-well lasers

Distributed-feedback emission from strained InGaAs-InGaAsP-InP quantum well lasers has been examined over a temperature range of 130 K to 300 K. Continuous single-mode output from 190 to 300 K with a side-mode-suppression ratio of about 10 dB was observed. The wavelength was 1.95 μm at 273 K and tuned at a rate of 0.13 nm/K. The current-tuning rate was 0.0043 nm/mA (-340 MHz/mA) at 273 and 283 K     

Some strength features of natural snow surfaces that affect snow drifting

The load, travel distance, and work index needed to break surface elements on 21 natural snow surfaces were measured with a motor-driven, spherical probe. The strongest and least brittle surfaces were fresh deposits of wind transported snow. The weakest surface was a new surface formed during snowfall with no sun and no wind. The most brittle surfaces were two cases of sun-softened snow that had refrozen before measurement. In new snow that had aged $\text{6–7}\text{1}\text{2}\text{h}$ with no sun and no wind, strength increased by a factor of 2–3, work index increased 10 times, and brittleness decreased by 4–9 times. On surfaces with both erosional and depositional features, the latter were stronger, less brittle, and had work indexes 10–100 times greater than the erosional features. The strength of snow surface elements as measured with the current hardness gage corresponded closely to the forces generated by saltating snow particles.     

Standardization of milk using cold ultrafiltration retentates for the manufacture of Swiss cheese: effect of altering coagulation conditions on yield and cheese quality

Fortification of cheesemilk with membrane retentates is often practiced by cheesemakers to increase yield. However, the higher casein (CN) content can alter coagulation characteristics, which may affect cheese yield and quality. The objective of this study was to evaluate the effect of using ultrafiltration (UF) retentates that were processed at low temperatures on the properties of Swiss cheese. Because of the faster clotting observed with fortified milks, we also investigated the effects of altering the coagulation conditions by reducing the renneting temperature (from 32.2 to 28.3°C) and allowing a longer renneting time before cutting (i.e., giving an extra 5 min). Milks with elevated total solids (TS; ∼13.4%) were made by blending whole milk retentates (26.5% TS, 7.7% CN, 11.5% fat) obtained by cold (<7°C) UF with part skim milk (11.4% TS, 2.5% CN, 2.6% fat) to obtain milk with CN:fat ratio of approximately 0.87. Control cheeses were made from part-skim milk (11.5% TS, 2.5% CN, 2.8% fat). Three types of UF fortified cheeses were manufactured by altering the renneting temperature and renneting time: high renneting temperature = 32.2°C (UFHT), low renneting temperature = 28.3°C (UFLT), and a low renneting temperature (28.3°C) plus longer cutting time (+5 min compared to UFLT; UFLTL). Cutting times, as selected by a Wisconsin licensed cheesemaker, were approximately 21, 31, 35, and 32 min for UFHT, UFLT, UFLTL, and control milks, respectively. Storage moduli of gels at cutting were lower for the UFHT and UFLT samples compared with UFLTL or control. Yield stress values of gels from the UF-fortified milks were higher than those of control milks, and decreasing the renneting temperature reduced the yield stress values. Increasing the cutting time for the gels made from the UF-fortified milks resulted in an increase in yield stress values. Yield strain values were significantly lower in gels made from control or UFLTL milks compared with gels made from UFHT or UFLT milks. Cheese composition did not differ except for fat content, which was lower in the control compared with the UF-fortified cheeses. No residual lactose or galactose remained in the cheeses after 2 mo of ripening. Fat recoveries were similar in control, UFHT, and UFLTL but lower in UFLT cheeses. Significantly higher N recoveries were obtained in the UF-fortified cheeses compared with control cheese. Because of higher fat and CN contents, cheese yield was significantly higher in UF-fortified cheeses (∼11.0 to 11.2%) compared with control cheese (∼8.5%). A significant reduction was observed in volume of whey produced from cheese made from UF-fortified milk and in these wheys, the protein was a higher proportion of the solids. During ripening, the pH values and 12% trichloroacetic acid-soluble N levels were similar for all cheeses. No differences were observed in the sensory properties of the cheeses. The use of UF retentates improved cheese yield with no significant effect on ripening or sensory quality. The faster coagulation and gel firming can be decreased by altering the renneting conditions.